synthesis of organometallic precursors for wnxcy...

SYNTHESIS OF ORGANOMETALLIC PRECURSORS FOR WNxCy DEPOSITION AND

DFT STUDY OF GAS PHASE SPECIES IN EQUILIBRIUM WITH CZTSSe

By

ARIJIT KOLEY

A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL

OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT

OF THE REQUIREMENTS FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA

2016

To my family

4

ACKNOWLEDGMENTS

First, I would like to thank Prof. Lisa McElwee-White. From day one she has been a

wonderful mentor. Her extensive knowledge in chemistry and its wide applications added with

her efficiency in learning new science quickly has always amazed me. I thank her for giving me

complete freedom in my research. We had long discussions on solving problems in the research

and what I really appreciated was that, without giving me the solution to the problem she guided

me through it which helped me to become an independent scientist.

I would like to thank my collaborator Prof. Timothy J. Anderson from Department of

Chemical Engineering for helping me understand the engineering aspect of my research. I also

thank his student Christopher O’Donohue for a wonderful collaboration which led to excellent

results.

I would like to thank my committee members Prof. Stephen A. Miller, Prof. Ronald K.

Castellano, Prof. George Christou and Prof. Helena Hagelin-Weaver for their valuable

discussions during my orals and departmental seminars. These discussions have helped me

improve my research.

I would like to thank Prof. Adrian E. Roitberg for helping me get started with the DFT

calculations for my CZTSSe project. I also thank Prof. Daniel R. Talham for his helpful

discussions in the Chemistry of Materials class.

I would like to thank both the present and past members of the McElwee-White group,

Sarah, Joseph, Ciera, Jenny, Randall, Richard, Yung-Chien, Kelsea, Michelle, Duane, Nathan,

Hang, Xiaoming, Chris, Will and Nate. A special thanks to Randall, Richard and Ciera for

mentoring me in when I started my research and Michelle for all her help in completing my

project.

5

I would like to extend my thanks to all my professors from my undergraduate and

masters institute. They have always inspired me and provided useful guidance which motivated

me to undergo higher studies.

Finally, I would like to thank my family and friends. First I thank parents and my in-laws

for their constant support, motivation and patience throughout my entire PhD career. A special

thanks goes to my wife Sweta Das and my sister Arpita Koley. They have been the greatest

friends all throughout my life. I also thank my close friends Subhadip Pal, Biswanath Dari,

Debjani Shihi, Tathagata Chowdhury, Amrita Chatterjee and Erika Taretto. They have helped me

a lot during the difficult times of my career.

6

TABLE OF CONTENTS

page

ACKNOWLEDGMENTS ...............................................................................................................4

LIST OF TABLES ...........................................................................................................................9

LIST OF FIGURES .......................................................................................................................11

LIST OF ABBREVIATIONS ........................................................................................................15

ABSTRACT ...................................................................................................................................17

CHAPTER

1 INTRODUCTION ..................................................................................................................19

Metal Halides and Carbonyls as Precursors ...........................................................................22 Amido Precursors ...................................................................................................................25

Imido and Hydrazido Precursors ............................................................................................31 Nitrido Precursors ...................................................................................................................39

2 DESIGN AND SYNTHESIS OF WN(NR2)(NRʹ2)(NRʺ

2) PRECURSORS ...........................41

Precursor Design .....................................................................................................................41

WN(NR2)(NiPr2)2 and WN(NR2)2(N

iPr2) ...............................................................................42 X-ray Crystal Structure Determination of 35 .........................................................................44 Design and Synthesis of Volatile Precursors ..........................................................................46

Structural Effects on Precursor Volatility ...............................................................................49 Thermogravimetric Analysis (TGA) of 35 and 36 .................................................................50

Thermolysis of Neat 35 ..........................................................................................................51 Spectroscopic Characterization of Compounds ......................................................................51

Computational Study of the Gas Phase Decomposition of 33 ................................................52 Mass Spectrometry .................................................................................................................54 WNxCy Film Growth from 35 .................................................................................................56 WNxCy Film Composition ......................................................................................................58 WNxCy Film Microstructure ...................................................................................................64

WNxCy Film Surface Roughness ............................................................................................66 WNxCy Film Density Measurements ......................................................................................67

Diffusion Barrier Testing ........................................................................................................69 Conclusion ..............................................................................................................................72 Experimental Section ..............................................................................................................73

General Procedures ..........................................................................................................73 Synthesis of WN(NMe2)(N

iPr2)2 (35) .............................................................................73

Synthesis of WN(NMe2)2(NiPr2) (36) .............................................................................74

General Procedure A .......................................................................................................75 Synthesis of WN(NMe2)(N

iBu2)2 (39) ............................................................................75

7

Synthesis of WN(N(CH2)5)3 (40) ....................................................................................75 Synthesis of WN(N(CH2)6)3 (41) ....................................................................................76 General Procedure B ........................................................................................................76 Synthesis of WN(NEt2)2(N

iPr2) (38) ...............................................................................76

Synthesis of WN(N(CH2)5)2(NiPr2) (42) .........................................................................77

Synthesis of WN(N(CH2)6)2(NiPr2) (43) .........................................................................77

General Procedure C ........................................................................................................78 Synthesis of WN(NEt2)(N

iPr2)2 (37) ...............................................................................78 Synthesis of WN(N(CH2)5)(N

iPr2)2 (45) .........................................................................78

Synthesis of WN(N(CH2)6)(NiPr2)2 (46) .........................................................................79

General Procedure D .......................................................................................................79 Synthesis of WN(NMe2)(N

iPr2)(NiBu2) (49) ..................................................................80

Synthesis of WN(NEt2)(NiPr2)(N

iBu2) (50) ....................................................................80 Synthesis of WN(N(CH2)5)(N

iPr2)(NiBu2) (51) ..............................................................81

Synthesis of WN(N(CH2)6)(NiPr2)(N

iBu2) (52) ..............................................................81

Diffusion Barrier Testing ................................................................................................82 DFT Calculations .............................................................................................................82

Thermolysis of 35 ............................................................................................................83 Crystallographic Structure Determination for 35 ............................................................84

3 CZTSSe: AN OVERVIEW ....................................................................................................85

Photovoltaics ...........................................................................................................................85 Silicon ..............................................................................................................................85

Dye-Sensitized Solar Cells ..............................................................................................86

Perovskites .......................................................................................................................86

Organic Photovoltaics .....................................................................................................87 CIGS, CdTe and CZTSSe ................................................................................................88

Deposition of CZTSSe ............................................................................................................89 Sputtering ........................................................................................................................89 Co-evaporation ................................................................................................................89

Pure Solution ...................................................................................................................90 Nanoparticle Based Deposition .......................................................................................90

Particle-Solution Deposition ...........................................................................................91 Computational Study ..............................................................................................................91

4 DFT STUDY OF GAS PHASE SPECIES IN EQUILIBRIUM WITH CZTSSe ..................94

Computational Methods ..........................................................................................................94

Sulfur Allotropes ....................................................................................................................96 Metal Sulfides .........................................................................................................................99 Metal Selenides .....................................................................................................................107 Bimetallic and Tetrametallic Clusters from Copper, Zinc and Tin ......................................111 Conclusion ............................................................................................................................114

Experimental Section ............................................................................................................114

8

APPENDIX

A NMR SPECTRA OF 35 AND 37 .........................................................................................116

B CRYSTALLOGRAPHIC DATA .........................................................................................118

Crystallographic Data for 35 ................................................................................................118

C COMPUTATIONAL DATA ................................................................................................150

Cartesian Coordinates for the Decomposition Pathway of 35 ..............................................150 Cartesian Coordinates for the Decomposition Pathway of 34 ..............................................168 Cartesian Coordinates for Cu2S and SnS2 ............................................................................184

Cartesian Coordinates for SnSe2 ...........................................................................................185 Cartesian Coordinates for Cu3Sn and Cu3Zn ........................................................................185

LIST OF REFERENCES .............................................................................................................187

BIOGRAPHICAL SKETCH .......................................................................................................196

9

LIST OF TABLES

Table page

2-1 Selected bond lengths (Å) and angles (°) for 35 ................................................................46

2-2 Sublimation conditions, symmetry and compound recovery for 33-47 and 49-52............49

2-3 Selected m/z values from the mass spectra of 33-45 and 45-50. .......................................55

4-1 DFT calculations for S4 (B3LYP/6-31G*) and comparison with literaturea. .....................96

4-2 Calculations for allotropes of sulfur (B3LYP/6-31G*) ......................................................98

4-3 Comparison of enthalpy, entropy, and Gibbs energy of formation of gaseous species

at 298.15 K.a .....................................................................................................................100


at 670.00 K.a .....................................................................................................................101


at 3000.00 K.a ...................................................................................................................102


at 298.15 K.a .....................................................................................................................108


at 3000.00 K.a ...................................................................................................................109


at 298.15 K.a .....................................................................................................................113


at 3000.00 K.a ...................................................................................................................113

B-1 Crystal data and structure refinement for 35 ....................................................................118

B-2 Atomic coordinates (x 104) and equivalent isotropic displacement parameters (Å2 x

103) for 35. U(eq) is defined as one third of the trace of the orthogonalized Uij

tensor. ...............................................................................................................................120

B-3 Bond lengths (Å) and angles (°) for 35 ............................................................................122

B-4 Anisotropic displacement parameters (Å2 x 103) for 35. The anisotropic displacement

factor exponent takes the form: -2π2[ h2 a*2U11 + ... + 2 h k a* b* U12. ........................144

B-5 Hydrogen coordinates (x 104) and isotropic displacement parameters (Å2 x 10 3) for

35......................................................................................................................................146

10

C-1 Optimized Cartesian coordinates of the GS in the decomposition pathway of 35. .........150

C-2 Optimized Cartesian coordinates for TS in the decomposition pathway of 35. ..............152

C-3 Optimized Cartesian coordinates for INT1 in the decomposition pathway of 35. ..........155



C-6 Optimized Cartesian coordinates for iPr2NH in the decomposition pathway of 35. .......167

C-7 Optimized Cartesian coordinates for the GS in the decomposition pathway of 34. ........168

C-8 Optimized Cartesian coordinates for TS1 in the decomposition pathway of 34. ............170


C-10 Optimized Cartesian coordinates for TS2 in the decomposition pathway of 34. ............175


C-12 Optimized Cartesian coordinates for Et2NH in the decomposition pathway of 34. ........183

C-13 Optimized Cartesian coordinates for Cu2S using M06L/LANL2DZ ..............................184

C-14 Optimized Cartesian coordinates for SnS2 using B3LYP/LANL2DZ ............................185

C-15 Optimized Cartesian coordinates for SnSe2 using B3LYP/LANL2DZ ...........................185

C-16 Optimized Cartesian coordinates for SnSe2 using M06L/LANL2DZ .............................185

C-17 Optimized Cartesian coordinates for Cu3Sn using B3LYP/LANL2DZ ..........................185

C-18 Optimized Cartesian coordinates for Cu3Sn using M06L/LANL2DZ ............................186

C-19 Optimized Cartesian coordinates for Cu3Zn using M06L/LANL2DZ ...........................186

11

LIST OF FIGURES

Figure page

1-1 PVD methods. A) Evaporation and B) Sputtering. ............................................................19

1-2 Representation of conformality in coverage of features. ...................................................20

1-3 Schematic diagram of CVD procedure. .............................................................................21

1-4 Reaction of metal chlorides with nitrogen and hydrogen. .................................................23

1-5 Reaction of TiCl4 with ammonia. ......................................................................................23

1-6 Formation of TiCl4•nNH3. .................................................................................................23

1-7 Reaction of TiCl4 with HMDS. ..........................................................................................24

1-8 Formation of W2N from WF6 and ammonia. .....................................................................25

1-9 Possible metallacycles from the intermediate Ti(NMeEt)2. ..............................................27

1-10 Tantalum precursors 3 and 4. .............................................................................................30

1-11 Formation of imido complexes from 5. .............................................................................31

1-12 Group IV bridging imido precursors..................................................................................32

1-13 Structure of 10....................................................................................................................33

1-14 Single source niobium precursors 11-14............................................................................34

1-15 Single source tantalum precursors 15-18. ..........................................................................34

1-16 Single source molybdenum precursors 19-23. ...................................................................35

1-17 Single source tungsten imido precursors 24-26. ................................................................36

1-18 Activation energy (Ea) for film growth vs N-C BDE. .......................................................37

1-19 Bridging imido and guanidinato tungsten precursors 27-29. .............................................37

1-20 Titanium hydrazido complexes, 30 and 31. .......................................................................38

1-21 Tungsten hydrazido precursor 32.......................................................................................39

1-22 Low temperature WNxCy deposition from 33. ...................................................................40

12

2-1 Arrhenius plot of growth rate (G) for films deposited with 33 depicting the two well-

defined growth regimes......................................................................................................42

2-2 Synthesis of 35-38..............................................................................................................43

2-3 Displacement ellipsoids drawing of 35 (molecule A is shown); ellipsoids are drawn

at 50% probability. .............................................................................................................45

2-4 Synthesis of 39-41..............................................................................................................47

2-5 Synthesis of 42-47..............................................................................................................47

2-6 Synthesis of 48 and 38. ......................................................................................................48

2-7 Synthesis of 49-52..............................................................................................................48

2-9 Thermolysis of 35. .............................................................................................................51

2-10 Decomposition pathway for 35. .........................................................................................53

2-11 Decomposition pathway for 34. .........................................................................................54

2-12 Growth kinetics comparing ln(G), where G is growth rate, versus inverse

temperature for films deposited from 33-35. The illustrated error bars are

representative of thickness measurements near the center of the substrate for multiple

samples and measurements. ...............................................................................................57

2-13 Evolution of the W 4f, N 1s, C 1s, and O 1s peaks with deposition temperature using

35. Relevant and nominal material BEs112 are superimposed onto the plots by a stick

pattern. ...............................................................................................................................59

2-14 Influence of precursor structure on the percentage of Nx-W, Ox-W, and Cx-W,

according to XPS peak deconvolution. ..............................................................................61

2-15 Elemental composition for films deposited from 33-35 at various deposition

temperatures, according to XPS. Note differences in concentration scale. .......................63

2-16 A) Grazing Incidence X-ray Diffraction (GIXD) patterns taken for films deposited

using compounds 34 and 35. B) Typical crystallographic planes for relevant

materials with respect to their preferred structures and according to their relative

intensities. ..........................................................................................................................65

2-17 Average surface RMS roughness for films deposited from 33-35. ...................................67

2-18 Correlation between deposition temperature and measured film density for

precursors 33-35.................................................................................................................68

2-19 XRD Patterns for as-deposited and post-annealed Cu/WNxCy/Si material stacks. ...........69

13

2-20 A) Plan-view image of etch-pit test for post-annealed Cu/WNxCy/Si stack at lower

magnification, B) plan-view image of etch-pit test for post-annealed Cu/WNxCy/Si

stack at higher magnification and C) plan-view image of etch-pit test for as-

deposited Cu/ WNxCy/Si stack, and D) image of failed post-annealed Cu/ WNxCy/Si

stack for comparison purposes. ..........................................................................................70

2-21 HRTEM image clearly showing smooth and distinct boundaries for a post-annealed

Cu/WNxCy/Si sample grown from 35. ...............................................................................71

2-22 A schematic of the etch-pit test. .........................................................................................82

3-1 Abundance of photovoltaic elements on earth’s crust. ......................................................88

3-2 Conventional unit cells for Kesterite structures. ................................................................92

4-1 Comparison between Thermocalc and DFT data for sulfur allotropes. .............................99

4-2 Optimized structures for Cu2S (M06L/LANL2DZ) and SnS2 (B3LYP/LANL2DZ). .....100

4-3 Enthalpy of formation of gaseous species as calculated from the SGTE SSUB4

database compared to the energies calculated from DFT at 298.15, 670.00 and

3000.00 K. ........................................................................................................................104

4-4 Entropy of formation of gaseous species as calculated from the SGTE SSUB4


3000.00 K. ........................................................................................................................105

4-5 Gibbs energy of formation of gaseous species as calculated from the SGTE SSUB4


3000.00 K. ........................................................................................................................106

4-6 Optimized geometry for SnSe2 with B3LYP (A) and M06L(B) .....................................107

4-7 Enthalpy of formation of gaseous species as calculated from the SGTE SSUB4

database compared to the energies calculated from DFT at 298.15 and 3000.00 K........110

4-8 Entropy of formation of gaseous species as calculated from the SGTE SSUB4

database compared to the energies calculated from DFT at 298.15 and 3000.00 K........110

4-9 Gibbs free energy of formation of gaseous species as calculated from the SGTE

SSUB4 database compared to the energies calculated from DFT at 298.15 and

3000.00 K .........................................................................................................................111

4-10 Optimized structures for Cu3Sn (A-M06L/LANL2DZ, B-B3LYP/LANL2DZ) and

Cu3Zn (C). ........................................................................................................................112

A-1 1H NMR of 35 (benzene-d6). ...........................................................................................116

A-2 gHMBC spectrum of 35 (benzene-d6). ............................................................................116

14

A-3 Variable temperature 1H NMR spectra for 35 (toluene-d8). ............................................117

A-4 Variable temperature 1H NMR spectra for 37 (toluene-d8). ............................................117

15

LIST OF ABBREVIATIONS

4PP

AACVD

AFM

ALD

APCVD

BDE

CALPHAD

CVD

DFT

DTA

ECP

FWHM

gHMBC

GIXD

HMDS

HOMO

HRTEM

ITO

LPCVD

LUMO

MOCVD

PV

PVD

QMS

4 Point Probe

Aerosol Assisted Chemical Vapor Deposition

Atomic Force Microscopy

Atomic Layer Deposition

Atmospheric Pressure Chemical Vapor Deposition

Bond Dissociation Energy

Computer Coupling of Phase Diagrams and Thermochemistry

Chemical Vapor Deposition

Density Functional Theory

Differential Thermal Analysis

Electron Core Potential

Full-Width-Half-Max

Gradient Heteronuclear Multiple Bond Coherence

Grazing Incidence X-ray Diffraction

Hexamethyldisilazane

Highest Occupied Molecular Orbital

High Resolution Transmission Electron Microscope

Indium Tin Oxide

Low Pressure Chemical Vapor Deposition

Lowest Unoccupied Molecular Orbital

Metal-Organic Chemical Vapor Deposition

Photovoltaics

Physical Vapor Deposition

Quadrupole Mass Spectrometer

16

RDS

RMS

SEM

SGTE

STP

TGA

VASP

XPS

XRR

Rate Determining Step

Root-Mean-Squared

Scanning Electron Microscope

Scientific Group Thermodata Europe

Standard Temperature and Pressure

Thermogravimetric Analysis

Vienna Ab initio Simulation Package

X-Ray Photoelectron Spectroscopy

X-ray Reflectivity

17

Abstract of Dissertation Presented to the Graduate School

of the University of Florida in Partial Fulfillment of the

Requirements for the Degree of Doctor of Philosophy

SYNTHESIS OF ORGANOMETALLIC PRECURSORS FOR WNxCy DEPOSITION AND


By

Arijit Koley

August 2016

Chair: Lisa McElwee-White

Major: Chemistry

WNxCy is known to be an excellent candidate as a Cu diffusion barrier in the

semiconductor industry. The tungsten nitride complex WN(NMe2)3 has been proven to be a

remarkable precursor for Aerosol Assisted Chemical Vapor Deposition (AACVD), which

involves volatilization by formation of aerosols from precursor solutions, to give WNxCy.

WNxCy films are obtained at temperatures as low as 125 ºC, which is important given the thermal

sensitivity of some chip components during processing. However, at low temperatures

WN(NMe2)3 was found to produce WNxCy films with low growth rates and high surface

roughness. Therefore, WN(NEt2)3 and WN(NMe2)(NiPr2)2 were synthesized through

transamination of WN(NMe2)3 with secondary amines and were found to address the

shortcomings of WN(NMe2)3. The precursors WN(NMe2)3, WN(NEt2)3 and WN(NMe2)(NiPr2)2

afforded films of thickness 30 nm, 5.5 nm and 5 nm, respectively, which passed tests as copper

diffusion barriers.

Atomic Layer Deposition (ALD) and other conventional CVD rely on evaporation of

liquid precursors or sublimation of solids, thus requiring precursors with high volatility. In order

18

to test the viability of this series of precursors for ALD, 17 precursors of the type WN(NR2)3 [R2

= combinations of Me, Et, iPr, iBu, piperidine, azepane] were prepared by transamination under

various conditions and evaluation of their volatility indicated that reduced symmetry was a major

contributor to the volatility.

CZTSSe (CuZnSnSSe) is one of the candidate materials for photovoltaic technology.

Recently it has gained interest as an earth abundant and eco-friendly material. The

thermochemistry for this material has not been studied thoroughly. The thermochemical data for

the possible gaseous binary species in equilibrium with the condensed phases of CZTSSe were

assessed by DFT using the Gaussian 09 package. Since thermochemical data for this material

derived from different models are scattered across the literature, computational results were

compared to existing databases (SGTE) as benchmarks to evaluate our methods in preparation

for calculation of unknown species. The DFT functionals B3LYP and M06L in conjunction with

the basis set LANL2DZ were used for calculations and compared to the values from the SGTE

database.

19

CHAPTER 1

INTRODUCTION

With the decreasing size of electronic devices, the importance of feature size in integrated

circuits (IC) is increasing rapidly. In modern IC, copper performs better as an interconnect

material than aluminum because the former has better conductivity and fewer electromigration

problems.1 Processing integrated circuits involves moderately high temperatures and in absence

of barrier materials Cu has a tendency to diffuse into the Si layer forming copper silicides.2 This

property results in the degradation of the copper-silicon boundary leading to the malfunctioning

of the electronic devices. Therefore, a diffusion barrier is required between the copper and

silicon layers.1 A good diffusion barrier should be able to prevent diffusion, maintain a good

adhesion with both Cu and Si without reacting with them and be prepared at the lowest possible

temperature.

A) B)

Figure 1-1. PVD methods. A) Evaporation and B) Sputtering.

These diffusion barriers can be prepared primarily in two ways: Physical Vapor

Deposition (PVD) and Chemical Vapor Deposition (CVD). There are two basic methods in

which PVD operates. One is evaporation (Figure 1-1A), where the target material (in solid or

liquid form) is heated under vacuum to convert it in to the vapor phase which is then transported

and deposited on the surface.3 The other method is known as sputtering (Figure 1-1B),4 where

20

the target material is bombarded with highly energized gaseous ions generated in a magnetron

assisted DC plasma which releases the required moieties from the target material. The ejected

moieties then fly through the plasma and are deposited on the substrate, which is usually placed

on the opposite side of the target material.3

In both the methods of PVD, after the material leaves the target source it is transferred

and deposited in a particular direction (Figure 1-1). Hence deposition procedure in PVD

encounters “line of sight” problems to create “shadows”, leading to non-uniform film growth and

incomplete coverage of substrate materials as shown by the poor barrier layer (grey) in Figure 1-

2.1 If a barrier layer is deposited non-uniformly, when copper is deposited (orange layer in

Figure 1-2) on top of the barrier material (through PVD) it can penetrate into the silicon substrate

as shown in Figure 1-2 for the poor deposition results.

Figure 1-2. Representation of conformality in coverage of features.

In CVD, the film deposition procedure is a surface phenomenon as shown in Figure 1-3.

First the precursors are transported in the vapor phase to the reaction chamber with the help of a

carrier gas. The precursors then either directly adsorb on the heated substrate or undergo gas

phase chemical transformation to an intermediate which then adsorbs on the heated substrate.

The adsorbed species then undergoes surface reaction (due to the generated heat on the substrate)

to transform into the desired material. At this point, any volatile byproducts still attached to the

21

material are desorbed from the surface of the material and removed from reaction chamber by

the carrier gas. The desired material then undergoes nucleation and film growth which results in

the formation of a conformal film on the substrate.5 Since the entire procedure is based on the

concept of adsorption of precursor materials on the substrate, CVD does not encounter the line of

sight problems of PVD and is successful in providing conformal film growth and across the

entire substrate. This CVD method requires precursor to be transported to the vapor phase which

indicates that the precursor have to be sufficiently volatile and thermally stable to be transported

to the reaction chamber without undergoing decomposition.

Figure 1-3. Schematic diagram of CVD procedure.

In AACVD, the precursor molecules are dissolved in a suitable solvent and then the

solution is converted into an aerosol with the help of a nebulizer. These aerosol droplets are

transferred in to the reaction chamber with the help of a carrier gas and deposition occurs in a

similar manner to the conventional CVD methods. An advantage of using AACVD is that

precursors with low volatility can also be used for deposition by dissolving them in an

appropriate solvent.5

22

Another precursor based deposition method is ALD. In ALD, the precursor transportation

is similar to that of CVD methods. Two sets of precursors are introduced into the chamber

sequentially. The first precursor gets adsorbed on the surface and then undergoes surface reaction

to form a single layered thin film. Once the entire substrate surface is covered, all other

byproducts and precursors (not adsorbed on the surface) are purged out of the system. This is

followed by the introduction of the second precursor which forms a single layered film on the

first film in a similar manner. This procedure is a self-limiting process and leaves only a

monolayer of deposited material from each precursor. The precursors required for this process

have to be extremely volatile and also thermally stable.6,7

Transition metal nitrides like TiN, ZrN, HfN, VN, NbN, TaN, CrN, MoN, WN have been

found to be useful in various industries, such as telecommunications, semiconductor, machine

tools and many others.8 TaNx are used in industry as diffusion barriers for IC but they require

another Ta layer with them for adhesion to the copper layer TaN alone does not adhere to copper

effectively. In contrast, WNx and WNxCy have all the properties to serve as diffusion barriers for

copper interconnect systems, including good resistance to Cu migration up to 750 ºC.8

An effective precursor which can provide a good barrier must be sufficiently volatile for

transport in the vapor phase. It should also have minimal toxicity and its synthesis should be as

simple as possible. A brief discussion of precursor design based on the ligand associated with the

metal center follows. The discussion covers evolution of precursors from the commercially

available halogenated and carbonylated metal compounds to the improved all nitrogen

coordinated single source precursors.

Metal Halides and Carbonyls as Precursors

Initially, metal nitrides were deposited in a co-reactant system where the precursors for

metal and nitrogen were different. The sources for metal have been metal halides or metal

23

carbonyls, whereas the source of nitrogen varied between nitrogen, ammonia, and primary or

secondary amines. Depending on the deposition procedure, sometimes hydrogen gas or zinc

pulses were used as co-reactants.

An early approach was using metal chlorides with nitrogen and hydrogen as co-reactants

as shown in Figure 1-4.9-11 The deposition for all the metal nitrides required temperatures higher

than 1000 °C to obtain significant growth rates at atmospheric pressure. High temperatures were

required because N2 is an unreactive source for reaction with metal chlorides. When deposition

was carried out by using TiCl4 and replacing the source of nitrogen with ammonia, TiN films

were obtained at 310 °C, with significant growths at 400 and 450 °C as shown in Figure 1-5.12

Figure 1-4. Reaction of metal chlorides with nitrogen and hydrogen.

Figure 1-5. Reaction of TiCl4 with ammonia.

Initial studies on the deposition of TiN using TiCl4 and NH3 indicated that the adduct

(TiCl4•nNH3) forms in the gas phase at room temperature, as shown in Figure 1-6.12 The number

of coordinated ammonia molecules depended on the temperature.12 Winter et al. reported

TiCl4(NH3)2 as a single source precursor for the deposition of TiN where they obtained good

quality films in the temperature range 475-600 °C.13 Similar deposition results were obtained

from TiCl4•nNH3 as those obtained from TiCl4 and NH3, indicating that the formation of the

adduct TiCl4•nNH3 was the first step in the deposition of TiN from TiCl4 and ammonia.

Figure 1-6. Formation of TiCl4•nNH3.

24

H2 has been used previously as a carrier gas for the deposition of TiN from TiCl4 and

ammonia. In order to understand the role of H2 in the deposition it was replaced by Ar, N2 and

He as carrier gases with TiCl4 and NH3, but similar TiN films were observed.12,14 Montree et al.

performed kinetic studies on the deposition using the same precursors and confirmed that H2

does not affect the film growth.14

The next attempt to decrease precursor deposition temperature was using substituted

amines instead of ammonia. Use of HMDS had a small effect on the deposition temperature of

TiN (Figure 1-7) from TiCl4, where films with higher growth rate were obtained at 300 °C.15

There was a huge decrease in deposition temperature when a similar strategy was applied for

APCVD of NbN and TaN from NbCl5 and TaCl5 respectively.16 When deposition of NbN was

performed using HMDS instead of ammonia, the deposition temperature decreased from 1000 °C

to 400 °C.16,17 A similar strategy for TaN resulted in decrease of deposition temperature from

900 °C to 550 °C.16,18 These results indicated that the formation of trimethylsilyl chloride played

a pivotal role in the decrease in deposition temperature.

Figure 1-7. Reaction of TiCl4 with HMDS.

Several approaches were made to improve the metal source by comparing different metal

halides and by replacing metal halides with metal carbonyls. Titanium tetraiodide was used

based on the concept that Ti-I bond strength (310 kJ/mol) is weaker than that of Ti-Cl (494

kJ/mol), but there was not a significant decrease in deposition temperature (430 °C vs 450 °C).19

The BDE is associated with the homolytic cleavage of the bond, whereas the reactions involved

in treating titanium halides and ammonia are all two electron process. When tantalum

pentabromide (Ta-Br bond strength = 120 kJ/mol) was used instead of tantalum pentachloride

25

(Ta-Cl bond strength = 172 kJ/mol), a decrease in deposition temperature to 425 °C was

obtained.20 For tungsten nitride, tungsten hexachloride was replaced with tungsten hexafluoride

due to the latter’s higher volatility and lower reduction temperature with H2 at ca. 300 °C to

achieve a deposition temperature of 450 °C as shown in Figure 1-8.21

Figure 1-8. Formation of W2N from WF6 and ammonia.

Tungsten nitride (WN) was also deposited through ALD using WF6 and ammonia as co-

reactants at 600 °C.22 When triethylborane was added to this deposition process as a co-reactant,

the deposition temperature drastically decreased to 313 °C.23 When diborane was used as an

additional reducing agent, the deposition temperature decreased to 200 °C.24 When a different

tungsten source, such as tungsten hexacarbonyl, WN films were formed with ammonia at 200

°C.25 In W(CO)6 the weaker tungsten-carbonyl covalent bonds dissociate easily upon heating

whereas for tungsten halides a nucleophile is required to break the tungsten halogen bonds.25

The most concerning problem with these coreactant systems was the byproducts. Figures

1-4, 1-5 and 1-8 show the formation of HCl or HF. HCl is hazardous to stainless steel process

equipment instruments and HF is harmful for silicon wafers. When carbonylated precursors are

used they produce carbon monoxide, which is also toxic. Figure 1-6 indicates that there is a

coordination complex formed in the beginning for dual source precursors, when the precursors

have empty co-ordination site. Therefore, optimal precursors should be halogen and carbon

monoxide free to eradicate the byproduct problem.

Amido Precursors

The approach to halogen free precursors started with using metal amido precursors and

ammonia as a coreactant. This design was initiated with the use of dialkylamido metal

26

complexes. Using amido metal complexes, deposition of metal (Group IV, V and VI) nitrides

were observed in the temperature range of 150-350 °C.8 TiN, ZrN, HfN, VN, NbN and MoN

were obtained by reacting Ti(NMe2)4,26-28 Zr(NMe2)4,

29 Hf(NMe2)4,29 V(NMe2)4,

30 Nb(NEt2)430

and Mo(NMe2)4,30,31 respectively, with ammonia. All the metal complexes here contain a set of

homoleptic ligands. Initial deposition studies from Ti(NMe2)4, Zr(NMe2)4 and Nb(NEt2)5 were

found to produce films with small quantities of carbon contamination.32 A comparative study of

film deposition from different metal amido precursors is discussed below.

An initial comparison has been done using precursors where the dialkylamido ligands on

the metal center have been varied. TiN films were produced from Ti(NMeEt)433 and Ti(NEt2)4.

34

Ti(NMeEt)4 was found to produce films with 18 % carbon content with respect to 30 % for

Ti(NEt2)4. This change was attributed to the homolytic bond dissociation of titanium and the

dialkylamido ligand to form a dialkylamido radical fragment. It was proposed that this radical

then undergoes fragmentation to form ethylene (identified in QMS as a component of

decomposition from Ti(NMeEt)4) and MeNH radical fragment, then the MeNH fragment further

decomposes to give one equivalent of amorphous carbon. Similar decomposition pathway from

Ti(NEt2)4 would result in 2 equivalent of amorphous carbon from each EtNH fragment.33

Although ethylene was found in the NIST database for the mass spectrum of

diethylamine, the database for mass spectrum of methylethylamine did not show the formation of

any ethylene, indicating that the ethylene was probably formed from a different fragment. There

is a possibility that a titanium metallacycle is formed through β-hydride elimination during the

decomposition of the precursor, as shown in Figure 1-9, and the ethylene is formed from the

fragment of N-alkyl dissociation. It is reported in literature that C-H activation for methyl group

is more favorable compared to the ethyl group due to sterics.35,36 Hence metallacycle 1 is favored

27

over 2, which could then lead to N-ethyl bond dissociation and formation of ethyl radical,

followed by the formation of ethylene. The possibility of β-hydride elimination and formation of

a metallacycle from Ti(NMe2)4 was supported through a recent density functional study using

M06L/LANL2DZ where this approach was found to be energetically more favorable than other

pathways.37 Formation of these metallacycles would also explain the carbon content in the films.

The carbon content of films produced from Ti(NMe2)4 was found to be around 10%. The

dimethylamido ligand fragments formed from Ti(NMe2)4 were not believed to be associated with

the surface reaction, leading to low carbon contamination in the films.34

Figure 1-9. Possible metallacycles from the intermediate Ti(NMeEt)2.

Films produced from Ti(NMeEt)4 had a high activation energy of 1 eV (23 kcal/mol)33

with respect to 18.5 kcal/mol for Ti(NMe2)433,34

and 15.2 kcal/mol for Ti(NEt2)4.34 Deposition

temperatures for Ti(NMeEt)4 and Ti(NEt2)4 were higher than Ti(NMe2)4, likely due to the

increasing steric bulk experienced during the formation of the metallacycle as shown in Figure 1-

9 compared to Ti(NMe2)4.34

With the precursor tBuTi(NMe2)3, where one dialkylamide ligand was replaced with a

tert-butyl group, the deposition temperature was found to be 300 °C, similar to the parent

precursor.38,39 All other film properties, such as carbon and hydrogen content in the films and the

growth rate, were also found to be similar for the films grown from both precursors.38 The

percentage of carbon incorporation was about 29% for films grown from tBuTi(NMe2)3 at 300

°C with respect to 32% for films grown from Ti(NMe2)4 at 350 °C.39 This similarity of carbon

28

incorporation could be attributed to the fact that both the precursors may undergo β-hydride

elimination to form a similar metallacycle during decomposition. It must also be noted that the

amount of titanium bound carbon was found to be similar in films deposited from Ti(NMe2)4 and

Ti(NEt2)439 which is consistent with both the precursors undergoing decomposition through a

similar transition state. The carbon in the deposits which are not metal bound could be formed

from the fragmentation of alkyl ligands, as shown in Figure 1-9.

Titanium precursors containing cyclic ligands have also been tested to determine whether

β-hydride elimination is one of the deposition pathways. Ti(N(CH2)4)4 and Ti(N(CH2)5)4 were

the two precursors used for this experiment. It was found that there was high carbon content in

the films, but the amount of titanium bound carbon was minimal. Because of the carbon being

part of a ring, formation of a titanium metallacycle would be unfavorable. The high carbon

content was probably due to the homolytic cleavage of the cyclic amido ligand from titanium

leading to the formation of the cyclic amido radical.39 This study indicated that precursors

containing ligands that prohibit metallacycle formation should result in minimum metal-bound

carbon in films. Synthesis of titanium precursors with bulky ligands (diisopropylamido and di-

tert-butylamido) surrounding the metal center was unsuccessful due to the steric conjestion

around the titanium.39

A comparison of titanium, zirconium, and hafnium nitride films produced from

Ti(NMe2)4, Zr(NEt2)4, and Hf(NEt2)4, respectively using ammonia as a co-reactant has been

done.28 Zirconium and hafnium precursors deposited films in the temperature range 200-400 °C,

whereas the titanium precursor deposited titanium nitride films at 150-450 °C. Hydrogen content

of the films from Ti(NMe2)4 was a high 33% at 150 °C, but it decreased to 10% at 400 °C.

Similarly, the hydrogen contents of the films derived from Zr(NEt2)4 and Hf(NEt2)4 were 38%

29

and 50% at 200 °C respectively, which decreased to 10.6% and 18.5% at 300 °C. The hydrogen

found in the films could be attributed to the M=NH (M=Ti, Zr and Hf) formation during the

ammonolysis of the precursors.28 The higher atomic sizes of Zr and Hf in Zr(NEt2)4 and

Hf(NEt2)4 favor ammonolysis with respect to titanium, which could explain the higher

percentage of hydrogen found in their films. At higher deposition temperatures, M=NH is

probably converted to MN which leads to the decrease in hydrogen content in all the films.

A similar study was also performed with the group V homoleptic metal-amido

complexes, V(NMe2)4, Nb(NEt2)4, Nb(NMe2)5 and Ta(NMe2)5 with ammonia as a co-reactant.40

Films produced from these precursors also exhibited similar trends of hydrogen content to those

from group IV metal amido complexes, with higher percentages of hydrogen content in Nb and

Ta compared to V.28 The growth rates for niobium and tantalum complexes were found to be

higher than those of vanadium precursors. This trend was probably due to the larger size of

niobium and tantalum, which favors ammonolysis, over vanadium. All the films deposited had

either minimal or no carbon and oxygen incorporation in the films.

Heteroleptic metal-amido complexes have also been used as precursors for the deposition

of metal nitrides. Both polymeric [Ti(NMe2)2(N3)2]n and monomeric Ti(NMe2)2(N3)2(py)2

precursors were synthesized for the deposition of TiN.41 It was observed that both the precursors

generated TiN films at substrate temperatures of 300-400 °C. However, the polymeric precursor

did not produce any film until the precursor temperature reached 90 °C at around 5 10-10 Torr

pressure, whereas the monomeric precursor produced films at precursor temperatures 25-90 °C

under same pressure conditions. This observation is probably due to the low volatility of

polymeric precursors with respect to the monomeric precursors.42,43 [Ti(NMe2)2(N3)2]n produced

films with higher carbon content than the Ti(NMe2)2(N3)2(py)2.41 Ti(NMe2)2(N3)2(py)2 was

30

found to produce films with carbon content of about 10% which is lower than Ti(NMe2)4,41

likely due to the decrease in the number of dialkylamido ligands in Ti(NMe2)2(N3)2(py)2.

Heteroleptic metal amido complexes of tantalum have also been used for deposition

studies. Complex 3 (Figure 1-10), containing chelating ligand, has been used for deposition of

tantalum nitrides through chemical vapor deposition.44 Complex 3 had similar thermal stability

compared to Ta(NMe2)5. Increasing the ring size of the chelating ligand and the size of the alkyl

group on the nitrogen of the chelating ligand improved the thermal stability and volatility of the

precursor. These complexes were found to have 20 °C higher onset temperature of

decomposition in TGA with respect to Ta(NMe2)5. The authors therefore chose complex 3 for

comparison of film growth with Ta(NMe2)5. However, there was an increase in deposition

temperature to 500 °C for 3 with respect to 150 °C for Ta(NMe2)5. The N/Ta ratio was found to

be around 0.9-1.3 for 3, which was similar to Ta(NMe2)5.44 Complex 4 (Figure 1-10) was

synthesized and used as a precursor for the deposition of tantalum nitride films at 340 °C.45

Films produced from 4 with ammonia as a co-reactant had no traces of carbon and oxygen.

These contaminants were also not observed when Ti(N(CH2)4)4 and Ti(N(CH2)5)4 were used for

deposition of titanium nitrides.39 The N/Ta ratio for the films from 4 was around 1.5, which was

higher than that obtained from 3 and Ta(NMe2)5.

Figure 1-10. Tantalum precursors 3 and 4.

31

Study of the deposition pathways from the metal amido precursors M(NMe2)4 (M=Ti, Zr)

started with the proposal that the dialkylamido ligands are cleaved from the metal one by one.32

However, a solution phase study was conducted46 using precursors M(NMe2)4 (M=Ti, Zr), which

indicated the formation of a metal imido complex [(M=NH)2]x during ammonolysis as an

intermediate.30 Films produced from the metal imido complex [Ti(NtBu)(NMe2)2]2, showed

similar deposition results, indicating that the metal imido bond formation is one of the

intermediates to TiN deposition.39

Figure 1-11. Formation of imido complexes from 5.

A subsequent attempt to deposit TiN from a single source precursor involved the use of

precursor 5, which was designed to test mixed halogen and amide ligands on titanium (Figure 1-

11). Deposition of TiN from 5 was observed at 500 °C.47 Through mass spectrometry (electron

impact 70 eV), they observed formation of dimeric (6) and monomeric (7) titanium imido

complexes (Figure 1-11) after heating complex 5 at temperatures of 190-240 °C. Appearance of

6 and 7 as fragments from 5 served as evidence for the formation of a metal-imido intermediate

during the decomposition of metal-amido precursors.

Imido and Hydrazido Precursors

The metal imido intermediate in Figure 1-11 suggested precursors containing M=N bond,

such as imido and hydrazido complexes, could serve as single source precursors. Bridging

titanium imido complex 8 (Figure 1-12) has been reported to generate films with similar percent

composition of elements compared to those obtained from Ti(NMe2)4.39 The similar bridging

32

imido complex 9 (Figure 1-12) containing a silylimido ligand was synthesized for the deposition

of metal nitrides. However, deposition from 9 mostly resulted in the formation of metal oxide

films, which was attributed to the leakage in precursor delivery system.48

Figure 1-12. Group IV bridging imido precursors.

A comparative study of film deposition and decomposition pathways for bridging and

terminal imido precursor was required. Mass spectrometric data for [TiCl2(NR)(NH2R)2]3 (where

R=alkyl groups) showed the presence of both monomeric and dimeric imido fragments.49 Here

the m/z value 380 indicated that the dimeric complex probably has a Ti2N2 structure, as shown in

Figure 1-12. Both the monomeric and dimeric fragments would undergo further decomposition

to form the metal nitride thin films.49 A monomeric terminal imido complex such as 10 (Figure

1-13) was found to be a better precursor with respect to tetrameric terminal imido complex

[TiCl2(NtBu)(NH2

tBu)]4. A complete study of the series of titanium precursors 10 (Figure 1-13)

was performed. In the complexes studied both the R groups and the coordinating ligands (L)

around the metal center were varied. When Me2NH was used as a ligand, it was found that only

two amines coordinated, unlike three for other ligands. The complex TiCl2(NtBu)(py)3 was found

to behave differently with respect to Ti(NMe2)4 as it produced TiN films with negligible carbon

contamination.50,51 This behavior was attributed to the fact that the tert-butyl group would

dissociate easily to form the volatile fragment isobutene, which can be lost easily during

33

deposition process. The coordinating ligands are pyridines, which also can dissociate easily from

the precursor and be carried away from the reaction chamber by carrier gas without affecting the

deposition process.51

Figure 1-13. Structure of 10.

A series of Cl3VNR (R= Me, C6H4CH3, tBu) precursors was synthesized to conduct the

depositions of VNxCy.52 Hydrogen as a carrier gas provided VNxCy films at lower temperatures

than nitrogen as a carrier gas. However, when hydrogen was used, HCl was formed as a

byproduct, probably from the σ-bond metathesis between H-H and V-Cl bonds.53,54 Comparison

of deposition from all three precursors indicated that the vanadium tert-butyl imido complex

could only be considered as a precursor for the deposition of VNxCy because it gives films at 500

°C.52 The other two complexes provided films at extremely high temperatures (900-1000 °C).

The high energy demand was probably due to the facile homolytic cleavage of the N-tBu, leading

to the formation of a stable tertiary radical which would transform to the volatile isobutene

fragment. Similar bond cleavage with other complexes would result in the formation of methyl

and aryl radicals, which have much lower stability with respect to the tertiary radical.

A chloride bridging dimeric niobium complex 11 (Figure 1-14) containing terminal imido

bonds, was synthesized for the deposition of NbN at around 600 °C.55 Although the films

contained some carbon contamination, they were found to be devoid of any chloride or silicon

contamination.55 Three new all nitrogen coordinated precursors 12, 13 and 14 were introduced as

potential precursors for the formation of NbN.56 A comparative study of deposition of NbN films

34

from 12 and 14 indicated that unlike 12, 14 did not need an additional reactive gas such as

ammonia to form carbon free films. This property was ascribed to the fact that the bidentate

guanidinate creates a coordinatively saturated environment around the Nb center to prevent β-

hydride elimination, and subsequently prevents the formation of the metal carbon bond during

the deposition process. Control of the Nb:N composition in the films is also easier from 14 as a

single source precursor than in case of 12.56

Figure 1-14. Single source niobium precursors 11-14.

Complex 15 (Figure 1-15) was initially thought to be an intermediate in the

decomposition of Ta(NEt2)5 to TaN. However further study suggested that Ta(NEt2)5 is

converted to 15 at temperatures above 100 °C implying that 15 is the true single source precursor

for the deposition of TaN. This postulate was supported by deposition of TaN films from 15 at

500-600 °C.32,57,58

Figure 1-15. Single source tantalum precursors 15-18.

Complexes 16,59 1760 and 1855 (Figure 1-15) were reported as precursors for the

deposition of TaN by LPCVD. The tert-butyl imido precursors 16 and 17 were found to deposit

35

TaN at lower temperatures (400 and 450 °C respectively), maintaining the trend followed by

tert-butyl imido complexes mentioned previously. Complex 18 produced films at 150 °C by

ALD with hydrazine as a reducing agent.61

Precursor 19 (Figure 1-16) was introduced for the deposition of MoN, where films were

obtained at 250 °C by ALD. A comparative study was performed with two other precursors,

where the methyl groups in 19 were replaced by ethyl (20) and isopropyl (21) groups (Figure 1-

16). DFT and DSC data indicated that the thermal stability of the precursors decreased with

increasing alkyl component. Complex 21 was found to be too thermally unstable for use in

deposition studies. This trend was attributed to the decomposition pathways proposed for the

precursors. DFT studies using B3LYP/LANL2DZ indicated that β-H migration, β-alkyl

migration and metallacyle formation via dialkylamine elimination were energetically more

favorable for bulky alkyl groups. Complex 20 and 21 were found to be stable enough to undergo

deposition to give MoN films by ALD.62,63

Figure 1-16. Single source molybdenum precursors 19-23.

A series of imido-guanidinato and imido-amidinato complexes was reported as potential

precursors for the deposition of MoN, and after comparing TGA and DTA data on all of them,

complex 22 (Figure 1-16) was used for the deposition of MoN by ALD at 500 °C.64,65 Deposition

of MoN was also performed by ALD using complex 23 (Figure 1-16), which contains both

36

nitrogen and sulfur containing ligands. Complex 23 combined with hydrogen plasma produced

Mo2N films at 300 °C.66

Complex 24 (Figure 1-17) was the first single source precursor synthesized for

applications in MOCVD of W2N.67 However, the deposition temperature for good quality films

was as high as 650 °C.67 The precursor 25 (Figure 1-17) was then synthesized for the deposition

of WN through ALD with ammonia being added as a co-reactant. This compound was the first

tungsten imido complex used for ALD. Complex 25 was reported to produce films of

composition WN1.1±0.1 at 250-350 °C by ALD.68

Figure 1-17. Single source tungsten imido precursors 24-26.

Complex 26 (Figure 1-17) was introduced as a single source precursor to deposit WNx

through AACVD at temperatures of 450 °C.69 Depositions were conducted using H2 as a co-

reactant. DFT study using the B3LYP functional combined with a split basis set (LANL2DZ for

metals and 6-31G(d) for non-metals) located a pathway for σ-bond metathesis between W-Cl and

H-H to form HCl (found experimentally) as a byproduct. A comparative study of all three

precursors of type 26 was performed to determine the rate determining step (RDS) of the

decomposition process. It was evident from the trend of the activation energy (Figure 1-18) that

the RDS was the imido nitrogen-carbon bond dissociation, which was supported by the DFT

calculations.53,54

37

Figure 1-18. Activation energy (Ea) for film growth vs N-C BDE.*

Complex 27 (Figure 1-19) was introduced as a new tungsten imido precursors for

LPCVD of WN, where for the first time a bridging imido was used for the deposition of WNx.70

Although the precursor had chloride ligands, the films were devoid of any chlorine

contamination. Oxygen contamination in the films reduced significantly by using ammonia as a

bleed gas instead of nitrogen. No change in carbon contamination was observed on changing the

bleed gas.70

Figure 1-19. Bridging imido and guanidinato tungsten precursors 27-29.

* Reprinted with permission from Bchir, O. J.; Green, K. M.; Ajmera, H. M.; Zapp, E. A.; Anderson, T. J.; Brooks,

B. C.; Reitfort, L. L.; Powell, D. H.; Abboud, K. A.; McElwee-White, L. J. Am. Chem. Soc. 2005, 127, 7825-7833.

38

Two new tungsten-imido-guanidinato complexes 28 and 29 (Figure 1-19) were

introduced as potential precursors for tungsten nitride deposition. However, after conducting

deposition studies it was concluded that they can produce tungsten nitride films only in the

presence of ammonia, ruling out their viability as single source precursors.71

With the evidence that the imido precursors undergo decomposition with the rate

determining dissociation of the imido nitrogen-carbon bond, replacing the nitrogen-carbon bond

with a weaker bond, such as a nitrogen-nitrogen bond, should produce films at lower

temperatures. Therefore, hydrazido complexes were of interest.

Figure 1-20. Titanium hydrazido complexes, 30 and 31.

A series of hydrazido complexes of the types 30 and 31 (Figure 1-20) were reported. The

former produced TiNCl films at 400 °C, whereas the latter deposited material at 600 °C.72

Chloride free titanium nitride films were observed from 30 at temperatures of 475 °C and above.

A comparative study indicated that during the deposition process the feasibility of the reduction

of the titanium center was dependent on the alkyl groups in 30.72

39

Figure 1-21. Tungsten hydrazido precursor 32.

A lower deposition temperature with respect to imido complexes was observed for

tungsten hydrazido complexes as predicted by the previous activation energy study on complex

26. The single source hydrazido complex 32 (Figure 1-21) was designed, and it produced

chloride free WNxCy films at 300 °C by AACVD. This deposition temperature was 150 °C lower

than the imido analogue 26.73 A gas phase Raman study on 32 supported the hypothesis for

precursor design. Fragments from the dissociation of the nitrogen-nitrogen bond in 32 were

observed in gas phase along with the formation of the protonated terminal nitrido bond. These

data were also supported by density functional theory (B3LYP/LANL2DZ) calculations.74

Nitrido Precursors

Evidence from mass spectrometry, Raman studies, and trapped decomposition fragments

has repeatedly implicated the formation of a terminal nitrido complex as an intermediate in the

decomposition pathway of metal imido and hydrazido complexes during deposition of metal

nitrides. Applying the precursor design strategy similar to the hydrazido precursors, use of

terminal nitrido metal complexes as single source precursors for the deposition of metal nitrides

should result in further lowering of deposition temperature.

Complex 33 (Figure 1-22) was prepared as a single source precursor. Deposition from 33

by AACVD formed WNx nanospheres at 75 °C and WNxCy films at 125 °C.75,76 Because any

deposition less than 400 °C is considered “low temperature” deposition, obtaining WNxCy at 125

40

°C was remarkable. The design that makes this possible evolved from the comparative study of

precursors of similar design in which the RDS was identified.

Figure 1-22. Low temperature WNxCy deposition from 33.

Although 33 provides low temperature deposition, its applications in other CVD

processes would be limited by its low volatility and decomposition during sublimation. A

comparative study of various precursors of similar design as 33 is discussed in the following

chapter.

41

CHAPTER 2

DESIGN AND SYNTHESIS OF WN(NR2)(NRʹ2)(NRʺ

2) PRECURSORS

Precursor Design

The manufacture of integrated circuits requires deposition of diffusion barrier material to

prevent the migration of Cu, its incorporation into Si and penetration into high porosity low-κ

dielectrics.†‡ Cu diffusion can increase contact resistances, produce contact layer embrittlement,

promote delamination from low-κ materials and generate energy levels within the bandgap of Si

that act as recombination centers.77 Currently, a physical vapor deposited (PVD) Ta/TaN bilayer

structure is used,78 but with the miniaturization of feature sizes, PVD has been projected to

become inadequate due to conformality issues deriving from the highly directional nature of

deposition. Chemical vapor deposition (CVD) and atomic layer deposition (ALD) are candidates

to succeed PVD technologies. Among materials considered for diffusion barrier applications are

transition metal nitrides and carbonitrides,40,65,79,80 and more recently self-forming barriers (e.g.,

MnSixOy).81-83 WNxCy has been discussed as a possible candidate given its low resistivity,

thermal and mechanical stability, resistance to recrystallization, ease of processing, and adhesion

to and compatibility with current IC materials.8,80

McElwee-White et al. have been using the CVD of WNxCy as a platform to examine

mechanism-based design of single source precursors84,85 featuring tungsten complexes with

nitrogen coordinated ligands such as imido, guanidinate, amidinate, amido, and hydrazido

moieties.84,86 One focus of this work has been lowering the deposition temperature (< 350 °C)87-

† Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;

Korotkov, R. Y.; Anderson, T. J.; McElwee-White, L. Chem. Mater. 2015, 27, 8326-8336. Copyright (2015)

American Chemical Society

‡ Reprinted with permission from McClain, K. R.; O’Donohue, C.; Koley, A.; Bonsu, R. O.; Abboud, K. A.;

Revelli, J. C.; Anderson, T. J.; McElwee-White, L. J. Am. Chem. Soc. 2014, 136, 1650-1662. Copyright (2014)


42

93 to decrease damage to adjoining thermally sensitive dielectric layers94 or contact level

structures.95,96 Identification of cleavage of the N-C bond as the rate-determining step in

deposition of WNxCy from the imido complexes Cl4(CH3CN)WNR (R = Ph, iPr, allyl)97

suggested a precursor design strategy in which the N-C bond was replaced by a weaker N-N

bond. The result was a lowering of the deposition temperatures from the 400-500 °C range

obtained with imido complexes98-100 to the 250-300 °C range observed for the analogous

hydrazido complexes.101 Elimination of that bond by moving to a terminal nitrido ligand instead

of imido or hydazido ligands was the next step in the evolving precursor design.

WN(NR2)(NiPr2)2 and WN(NR2)2(NiPr2)

McElwee-White et al. then reported the design and synthesis of the nitrido complex

WN(NMe2)3 and the resulting CVD of WNx nanospheres75 and WNxCy thin films76 from 33 at

temperatures as low as 75 °C and 125 °C, respectively. However, the growth rate for the films

grown from 33 was found to be low at lower temperatures (Figure 2-1). This discovery indicated

that although we were able to achieve low temperature deposition, high growth rates for film

deposition were yet to be achieved.

Figure 2-1. Arrhenius plot of growth rate (G) for films deposited with 33 depicting the two well-

defined growth regimes.§

§ Reprinted with permission from McClain, K. R.; O’Donohue, C.; Koley, A.; Bonsu, R. O.; Abboud, K. A.;

Revelli, J. C.; Anderson, T. J.; McElwee-White, L. J. Am. Chem. Soc. 2014, 136, 1650-1662.

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6

T (°C)

ln(G

) (Å

/min

ute

)

1000/T (K-1)

150250350450550650 200300

43

Hence we needed to synthesize more precursors of similar design but with wide variety

of ligands and compare the films grown from them. After 33 was synthesized in high yield from

WN(OtBu)3 and Zr(NMe2)4,75 synthesis of other WN(NR2)3 complexes from WN(OtBu)3 was

explored. As expected, the reaction of WN(OtBu)3 with Zr(NEt2)4 in toluene resulted in complete

amide/alkoxide exchange, as observed in the 1H NMR spectra of the product mixture. However,

the product, WN(NEt2)3 (34), could not be isolated by selective crystallization or sublimation.

Transamination from 33 using dialkylamines was chosen as a strategy due to the near

thermoneutrality of the exchange and the relative volatility of the dimethylamine product.

Indeed, reaction of 33 with excess diethylamine (60 equiv) at reflux, either neat or in pentane

solution, for 3 h resulted in complete substitution to produce 34. The crude product was purified

easily by recrystallization from hexamethyldisiloxane, resulting in a high yield (85%) of ana-

lytically pure 34.

WN(NMe2)(NiPr2)2 (35) and WN(NMe2)2(N

iPr2) (36) were obtained by manipulation of

the reaction conditions (Figure 2-2). Transamination of 33 in refluxing diisopropylamine allowed

for the selective synthesis of 35 (Figure 2-3), while conducting the transamination of 33 with

excess diisopropylamine in refluxing pentane solution resulted in selective formation of 36. In

both cases, the product could be purified by recrystallization.

Figure 2-2. Synthesis of 35-38.

44

The remaining dimethylamide groups of 35 and 36 were cleanly replaced by

transamination with excess diethylamine in refluxing benzene or pentane solution to produce

WN(NEt2)(NiPr2)2 (37) and WN(NEt2)2(N

iPr2) (34) respectively. Analytically pure 37 was more

efficiently obtained by sublimation owing to its very high solubility while pure 38 was obtained

by recrystallization from hexamethyldisiloxane.

X-ray Crystal Structure Determination of 35**

Complex 35 was chosen for X-ray structure determination because of its

heterosubstituted sterically crowded ligand environment and temperature dependent NMR

spectra. Variable temperature NMR for 35 (Figure A-3) shows a coalescence of the two

diastereotopic methyl groups at -25 °C and the activation energy barrier calculated from the

spectra was around 52.15 kJ/mol. Crystals suitable for crystallography were grown from

concentrated hexamethyldisiloxane solution at low temperature. The asymmetric unit of 35

consists of the three chemically equivalent but crystallographically independent complexes: A, B

and C (Table 2-1). As seen in Figure 2-3, 35 adopts a distorted tetrahedral geometry. The

average (A, B and C) W-N (W≡N) bond length of 1.683(3) in 35 is very similar to that in 33

[W≡N 1.680(2)] and slightly longer than in WN(N(Ar)iPr)366 (Ar = 3,5-C6H3Me2) [W≡N

1.669(5)]. As in 33,63 the W-Namide bond lengths of 35 are shorter [W-Navg. 1.953(4)] than in

WN(N(Ar)iPr)3 (Ar = 3,5-C6H3Me2) [W-N(Ar)iPr 1.972(3)], a result consistent with the stronger

donor (σ, π) character of –NR2 (R = Me, iPr)67 versus -N(Ar)iPr (Ar = 3,5-C6H3Me2). The total

bond angles around N2/N3/N4 in 35 are consistent with sp2 hybridization [359.9(3), 360.0(3) and

360.1(4)° respectively], and the amide planes of 35 are parallel to the W≡N axis, allowing π

** X-ray structure determination was carried out by Dr. Khalil Abboud, Department of Chemistry, University of

Florida.

45

donation into the W based dx2

-y2

and dxy orbitals. A distortion towards trigonal pyramidal

geometry is observed in 35, evidenced by the contraction [{N≡W-N}vg., 105.15(16)°] and

expansion [{N-W- N}avg., 113.42(15)°] of bond angles around W. As in 35, this is caused by

steric repulsion between the more bulky amide groups and a tendency for low overlap between

fully occupied bonding orbitals.

Figure 2-3. Displacement ellipsoids drawing of 35 (molecule A is shown); ellipsoids are drawn

at 50% probability.

46

Table 2-1. Selected bond lengths (Å) and angles (°) for 35

Bond Bond Length (Å) Bond Bond Angle (°)

W1A-N1A 1.688(3) N1A-W1A-N2A 105.47(15)

W1B-N1B 1.679(3) N1B-W1B-N2B 106.04(15)

W1C-N1C 1.681(3) N1C-W1C-N2C 104.95(16)

W1A-N2A 1.949(3) N1A-W1A-N3A 104.52(12)

W1B-N2B 1.952(4) N1B-W1B-N3B 104.50(16)

W1C-N2C 1.957(4) N1C-W1C-N3C 104.84(16)

W1A-N3A 1.950(3) N1A-W1A-N4A 105.45(16)

W1B-N3B 1.951(4) N1B-W1B-N4B 106.20(13)

W1C-N3C 1.955(3) N1C-W1C-N4C 106.17(12)

W1A-N4A 1.961(4) N2A-W1A-N3A 113.33(15)

W1B-N4B 1.948(3) N2B-W1B-N3B 110.87(14)

W1C-N4C 1.945(3) N2C-W1C-N3C 111.62(15)

N2A-W1A-N4A 113.65(14)

N2B-W1B-N4B 115.00(14)

N2C-W1C-N4C 115.55(14)

N3A-W1A-N4A 113.29(15)

N3B-W1B-N4B 113.27(14)

N3C-W1C-N4C 112.64(15)

Design and Synthesis of Volatile Precursors

Since volatility of the complexes is important for application in CVD and ALD,84,102 the

vapor-phase transport of these complexes was tested by sublimation. In these studies, 35 and 36

were found to be more volatile than 33 and 34, despite their higher molecular weights (Table 2-

2). The increase in volatility in going from homoleptic ligand sets to heteroleptic ones has been

previously noted and ascribed to perturbation of crystal packing forces by lowered

symmetry.84,103,104 It has also been postulated that steric bulk around the metal center contributes

to volatility by hindering intermolecular interactions. The higher volatility of 35 and 36 led us to

synthesize additional complexes containing heteroleptic sets of ligands, in which the lowered

symmetry is complemented by varying degrees of steric bulk in the dialkylamide ligands.

47


The isobutyl derivative 39 was synthesized by refluxing 33 with excess diisobutylamine

in pentane for 12 h (Figure 2-4). Reaction of 33 with excess piperidine or azepane under the

same reaction conditions resulted in replacement of all three NMe2 ligands to afford 40 or 41.

This is most likely due to the smaller cone angles of cyclic secondary amines such as piperidine

(121°) and azepane when compared to diisopropylamine (137°) and diisobutylamine (138°).


Compounds 42-47†† were synthesized from 33 in a one pot strategy which takes

advantage of the steric demand of the NiPr2 ligand to limit the extent of substitution in the

presence of excess diisopropylamine (Figure 2-5).

†† Compounds 44 and 47 were synthesized by Michelle M. Nolan.

48

Figure 2-6. Synthesis of 48 and 38.

Attempts to synthesize the asymmetrical complex 48 by controlling the stoichiometry of

less sterically hindered amines were unsuccessful. Reflux of 36 with one-third of an equivalent

of diethylamine in pentane resulted in the formation of a mixture of 48 and 38 (Figure 2-6).

Efforts to separate 48 and 38 through extraction, crystallization or sublimation did not provide a

pure sample of either product.


The alternative asymmetrical target complex 49, which contains the more sterically

demanding diisobutylamido ligand in place of the diethylamido ligand of`48 could be prepared

by a one pot synthesis strategy (Figure 2-7) that affords 49 in 50% yield. Further substitutions of

the dimethylamido ligand in 49 could be obtained by reaction with excess diethylamine,

piperidine and azepane in refluxing pentane to obtain 50, 51 and 52 respectively.

49

Structural Effects on Precursor Volatility

The effect of substituent choice on volatility and thermal stability of complexes 35-47

and 49-52 was assessed by sublimation. Complex 39 contains NR2 groups that have a nearly

identical cone angle (138° for NiBu2) to those of 27 (137° for NiPr2)105 but are of higher

molecular weight. Precursor 39 was found to be less volatile than 35 (Table 2-2), suggesting

that, as expected, the lower molecular weight of the isopropyl derivative 35 dominates volatility

when the steric profiles are similar.

Table 2-2. Sublimation conditions, symmetry and compound recovery for 33-47 and 49-52

Complex Ligand(R) Ligand(Rʹ) Ligand(Rʺ) Symmetry Pressure

(mTorr) T (°C)

%

Recovery

33 Me Me Me D3v 150-250 90-105 55

34 Et Et Et D3v 150-250 75-80 55

40 Piperidine Piperidine Piperidine D3v 150-250 70-80 45

41 Azepane Azepane Azepane D3v 150-250 75-85 40

36 Me Me iPr Cs 350-450 65-70 35

38 Et Et iPr Cs 250-350 62-68 30

42 Piperidine Piperidine iPr Cs 150-250 60-70 45

43 Azepane Azepane iPr Cs 150-250 70-80 35

44 nPr nPr iPr Cs 150-250 65-70 55

39 Me iBu iBu Cs 150-250 80-85 40

35 Me iPr iPr Cs 350-450 65-70 40

37 Et iPr iPr Cs 250-350 58-68 30

45 Piperidine iPr iPr Cs 150-250 55-65 40

46 Azepane iPr iPr Cs 150-250 60-65 35

47 nPr iPr iPr Cs 200-300 50-55 35

49 Me iBu iPr C1 150-250 45-55 55

50 Et iBu iPr C1 150-250 40-50 60

51 Piperidine iBu iPr C1 150-250 42-50 50

52 Azepane iBu iPr C1 150-250 42-50 45

Reduced symmetry about the metal center also has the expected effect on precursor

volatility.12, 33, 34 Homoleptic complexes with D3v symmetry (33, 34, 40 and 41) have lower

50

volatilities (as measured by sublimation temperature) compared to heteroleptic complexes with

Cs symmetry (35-39 and 42-47). Among the precursors with Cs symmetry, those with two

diisopropylamido groups have higher steric crowding around the tungsten center, which makes

them more volatile compared to the precursors with one diisopropylamido group. The highest

volatilities were found for the asymmetrical complexes with C1 symmetry (49-52), which all

sublimed at temperatures below 50 °C at 150-200 mTorr. Complex 50 was found to sublime at

room temperature at 150-200 mTorr slowly, where the sublimation was found to be ongoing for

48 h without any decomposition of the crude sample.

Thermogravimetric Analysis (TGA) of 35 and 36

The TGA of 35 (Figure 2-8) is consistent with sublimation of the compound at

approximately 230 °C at atmospheric pressure. This result confirms that complex 35 is

sufficiently stable to survive the reduced pressure sublimation described in Table 2-2. In

contrast, some of the precursors, such as 36, could not be sublimed at atmospheric pressure

because their decomposition temperatures were too low.

Figure 2-8. TGA Plot for 35 and 36.‡‡

‡‡ Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



51

Thermolysis of Neat 35

Thermolysis of 35 was performed to identify the volatile byproducts of its decomposition

and provide information on possible reaction pathways for deposition of WNxCy. To obtain

samples of the pyrolysis products, complex 35 was heated to ~260 °C under 1 atm of argon and

the condensate was collected at –78 °C. A brown black residue was left after thermolysis. GC-EI

MS of the condensate confirmed the presence of the pyrolysis product diisopropylamine. Also

detected in the mass spectra were imine 53, isopropylamine and acetone. The isopropylamine

and acetone are the products of hydrolysis of 53 by adventitious water introduced into the sample

during trapping and handling. (Figure 2-9).

Figure 2-9. Thermolysis of 35.

Spectroscopic Characterization of Compounds

The 1H and 13C NMR spectra of complexes 36, 38, 42-44 and 53 displayed sharp first-

order spectra indicative of unrestricted rotation about all W-Namide bonds, as found in 33. The

NMR spectra of complexes 35, 37, 39-41, 45-47 and 49-52 exhibited diastereotopic methyl

groups on the diisopropylamide ligands. This was evidenced by the appearance of two doublets

in the 1H NMR spectra (Figure A-1). To confirm that the peaks emerge from the two methyl

groups on the same isopropyl and not from methyls on two different isopropyl groups, we

obtained a 2D NMR with 35 in benzene-d6. The gHMBC spectrum (Figure A-2) shows a

coupling between the proton at 1.26 ppm and the carbon at 26.4 ppm with another coupling

between the proton at 1.34 ppm and the carbon at 25.5 ppm. This indicates that the two peaks

arise from the two methyl groups on the same isopropyl moiety.

52

The variable temperature 1H NMR spectra of 35 (Figure A-3) and 37 (Figure A-4)

indicated restricted W-Namide bond rotation at lower temperatures, evidenced by coalescence of

the diastereotopic methyl doublets into a broad singlet. The methyl doublets coalesce at -25 °C

and -5 °C for 35 and 37 respectively.

Computational Study of the Gas Phase Decomposition of 33

A DFT study was carried out to explore possible mechanistic pathways leading to loss of

diisopropylamine, a thermolysis product of 35 (Figure 2-9).§§ For the lowest energy gas phase

pathway that was located (Figure 2-10), the first step was unimolecular β-proton abstraction by

the adjacent amide, which occured via a relatively high energy transition state (ΔG‡ = 40.2

kcal/mol; ΔH‡ = 39.2 kcal/mol). Formation of INT1 was followed by the coordination of another

molecule of 35 to generate the bimetallic INT2 in a slightly exothermic step. Although the

transition state linking INT1 to INT2 could not be located computationally, addition of 35 to the

coordinatively unsaturated INT1 likely has a very low barrier. Likewise, the transition state from

INT2 to INT3 was not located, but loss of diisopropylamine from the sterically crowded INT2 is

also likely to have a moderately low barrier. Attempts to locate pathways in which two

molecules of 35 reacted directly in the gas phase were unsuccessful. The inability to locate a

bimolecular pathway is in contrast to computational results on the less sterically hindered

dimethylamido complex 33,106 for which bimolecular gas phase reaction was preferred over the

unimolecular pathway. In a related pathway involving the decomposition of WN(NEt2)3 (Figure

2-11), the energy barrier for formation of the bimolecular transition state (TS2) and the energy

barrier for the subsequent step involving elimination of amine (INT2) were isoenergetic (ΔΔG =

0.3 kcal/mol).

§§ All DFT studies for decomposition pathways of 34 and 35 were performed by Richard O. Bonsu.

53

Figure 2-10. Decomposition pathway for 35.***

*** Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



54

Figure 2-11. Decomposition pathway for 34.†††

Mass Spectrometry

Since the fragmentation patterns observed during mass spectrometry often correlate well with

observed CVD decomposition pathways,97,107,108 the positive ion CI (chemical ionization) mass

spectra of compounds 35-39, 49, 50, 52 and DART-TOF for 42-47, 51 were obtained (Table 2-

3). For all compounds, the appropriate [M+H]+ ion was observed in high relative abundance,

indicating the moderate stability of these thermally sensitive compounds under the ionization

conditions. All compounds had additional tungsten-containing fragment ions. Some of these

††† Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



49.5

24.4 18.6

GS

INT1

INT248.9

23.1

3.10.0

ΔGΔH

TS2

18.9 16.0

TS1

55

fragments correspond to loss of dialkylamine from monomeric [(M-HNR2)+H]+ and dimeric

[(M2-HNR2)+H]+ species. Heterosubstituted compounds generated fragments corresponding to

loss of both types of dialkylamines from monomeric and dimeric species, but in most cases the

relative abundances of these fragments were very low (<1%). However, the mass spectrum of

compound 36 clearly displayed all four possible fragments {[(M2-HNMe2)+H]+, [(M2-

HNiPr2)+H]+, [(M-HNMe2)+H]+, [(M-HNiPr2)+H]+} with significant relative abundance.

Table 2-3. Selected m/z values from the mass spectra of 33-45 and 45-50.

Compound (MW) Selected Ions (m/z)(Relative Abundance) [Formula]

35 (442) 443(23.4) [M+H]+

36 (386) 728(26) [(M2-HNMe2)+H]+; 672(11) [(M2-HNiPr2)+H]+; 387(96)

[M+H]+; 342(6) [(M-HNMe2)+H]+; 286(2) [(M-HNiPr2)+H]+

37 (470) 471(83) [M+H]+; 398(1) [(M-HNEt2)+H]+; 370(2) [(M-HNiPr2)+H]+

38 (442) 812(1) [(M2-HNEt2)+H]+; 443(15) [M+H]+

39(498) 499(100) [M+H]+; 868(35) [(M2-iBu2NH)+H]+; 953(19) [(M2-

Me2NH)+H]+

40 (448) 449(56) [M+H]+; 364(13) [(M-C5H10NH)+H]+; 812(1) [(M2-

C5H10NH)+H]+

41 (492) 493(100) [M+H]+; 393(2) [(M-C6H12NH)+H]+

42 (466) 467(1) [M+H]+; 847(10) [(M2-C5H10NH)+H]+

43 (494) 495(6) [M+H]+; 890(100) [(M2-iPr2NH)+H]+

44 (498) 499(5) [M+H]+; 896(1) [(M2-iPr2NH)+H]+

45 (482) 483(3) [M+H]+; 965(2) [M2+H]+

46 (496) 497(4) [M+H]+; 893(4) [(M2-iPr2NH)+H]+

47 (498) 499(100) [M+H]+; 896(2) [(M2-iPr2NH)+H]+; 997(97) [M2+H]+

49 (470) 471(62) [M+H]+; 426(19) [(M-Me2NH)+H]+; 812(2) [(M2-iBu2NH)+H]+; 896(2) [(M2-Me2NH)+H]+

50 (498) 426(7) [(M-Et2NH)+H]+; 499(18) [M+H]+; 868(5) [(M2-iBu2NH)+H]+; 896(1) [(M2-

iPr2NH)+H]+

51 (510) 511(100) [M+H]+; 920(30) [(M2-iPr2NH)+H]+; 892(32) [(M2-

iBu2NH)+H]+

52 (524) 525(31) [M+H]+; 920(1) [(M2-iBu2NH)+H]+

56

WNxCy Film Growth from 35

An Arrhenius plot of the film growth kinetics for depositions using 35 (green) presented

in Figure 2-12 dissolved in pyridine (AACVD) showed three growth regimes; a kinetically

limited regime at low temperatures with an apparent activation energy of 0.330 ± 0.016 eV, a

mass transfer limited regime, and a parasitic reaction regime at high temperatures.‡‡‡ As shown

in Figure 2-12, this behavior is different from that observed in depositions using 33 (black) and

34 (red) where only two growth regimes exist: mass transfer limited and parasitic reaction.

Apparently the low temperature surface deposition reactions for 33 and 34 are faster than the

mass transfer rates. Conversely, the observation of a low temperature kinetic limitation using 34

indicates the rate limiting reaction step is slower than the mass transfer rate in the lower

temperature range. The greater steric bulk of 35 (vs. 33 and 34) and the computational evidence

for bimolecular decomposition steps are consistent with a greater kinetic limitation for film

growth from 35 at low temperatures. This kinetic barrier, however, is still small for typical CVD

conditions where apparent activation energies are normally above 0.5 eV.109 It has previously

been argued that the lowest energy pathway for film deposition is most likely the result of

intermolecular interactions between surface bound species or a surface-gas species interaction.

In the mass transfer limited regime, there is a noticeable difference in growth rate among

the precursors with the average growth rate increasing as 33 < 35 < 34. In general, growth rate

temperature dependence under mass transfer limited conditions follows a power law, Tn; where n

is typically 1.7-1.8 for a vertical down flow design.97 Depositions using 33, 34, and 34 exhibit

values of 1.3, 2.1 and 2.0 for n, respectively. A value of 2.1 has been previously reported for a

different precursor in the same reactor.97

‡‡‡ Film deposition and data collection were carried out by Christopher O’Donohue.

57

Figure 2-12. Growth kinetics comparing ln(G), where G is growth rate, versus inverse

temperature for films deposited from 33-35. The illustrated error bars are

representative of thickness measurements near the center of the substrate for multiple

samples and measurements.§§§

At higher deposition temperatures (> 400 °C), the growth rates from 33, 34, and 35

decrease with increasing temperature. This trend is associated commonly with parasitic reactions

resulting in wall deposition upstream of the heated susceptor, premature gas phase reactions,

and/or desorption of surface bound species. The apparent activation energies for this regime are

−0.386 ± 0.008 eV, −0.385 ± 0.009 eV, and −0.200 ± 0.020 eV for 33, 34, and 35, respectively.

Since parasitic reactions decrease the reactant concentration available for deposition and thus

deposition rate, the reported deposition activation energies are negative. It is noted that the mass

transfer to parasitic reaction controlled transition temperatures are similar for each precursor,

suggesting a similar parasitic reaction. Steric control of the parasitic high temperature process is

consistent with the observed trend, where the apparent activation energies for 33 and 34 are

§§§ Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



58

nearly identical, while that of 36 is significantly higher. The A values for methyl and ethyl are

1.74 and 1.75, respectively, while the value for isopropyl is 2.15,110 indicating a much larger

steric profile for the isopropyl substituents in 35 than for the methyl and ethyl substituents in 33

and 34.

WNxCy Film Composition

X-ray photoelectron spectroscopy (XPS) was used to determine elemental composition

and atomic valence states in the films. W, N, C, and O are the only elements evident in the

deposits from 35 within the detection limit of ~1% (Figure 2-13). Similar composition data for

material grown from 33 and 34 were reported previously.106,111

In the XPS data for deposits from 34, the W 4f doublet peak was consistent with

contributions from three separate tungsten compounds, whose nominal binding energies (BEs)

values112 are depicted in the superimposed stick patterns. Although the WNx and WC1-x peaks

were separated by approximately 0.2 eV, they are illustrated as a single WNxCy peak.

In the N XPS, the stick patterns are representative of nominal BEs for WNx and CNx at

397.5 eV and 400.2 eV, respectively; although they are labeled as WNxCy and “Free N” for ease

of illustration. At the deposition temperature of 100 °C the primary N 1s peak contained an

asymmetric tail at higher BEs that could be fitted with a peak at a BE of 400.1 eV, which is

consistent with nitrogen in the form CNx. This suggests that 35 may not fully decompose at 100

°C. At all other deposition temperatures, the only peak present was one located at 397.9 ± 0.2

eV, which is indicative of partially oxidized WNx.

Typical BEs for C 1s peaks from WC1-x reside around 283.5 eV, amorphous C between

284.5 eV and 285.0 eV depending on its nature, and CNx lies at approximately 286.0 eV (Figure

2-13). In the material deposited from 35 at 100 °C, small amounts of CNx (~11%) could be

detected. Spectra from materials deposited at all other deposition temperatures revealed only

59

peaks corresponding to amorphous C (labelled as “Free C”) and carbidic C (i.e., Cx-W). The

average amorphous C content at depositions below 300 °C was 23 ± 1%, whereas from 300-450

°C it was 29 ± 1%, and above 450 °C it increased to 43 ± 1% at 650 °C.

Figure 2-13. Evolution of the W 4f, N 1s, C 1s, and O 1s peaks with deposition temperature

using 35. Relevant and nominal material BEs112 are superimposed onto the plots by a

stick pattern.****

Adventitious nonstoichiometric tungsten oxide (WOx where 2.0 < x < 3.0) was also

detected in the XPS. Although the sub-peaks corresponding to WNxCy were relatively constant

for all deposition temperatures at 32.3 ± 0.1 eV and 34.3 ± 0.1 eV for W 4f7/2 and W 4f5/2,

respectively, the WOx peaks shift from 35.8 ± 0.2 eV and 37.6 ± 0.2 eV (below 250 °C) to 35.0 ±

**** Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



60

0.1 eV and 36.7 ± 0.2 eV (at and above 250 °C) for W 4f7/2 and W 4f5/2 peaks, respectively. This

suggests that higher temperature growth results in adventitious WOx that is less fully oxidized.

Observation of WOx in the W XPS region of films grown using 35 as a precursor can be

corroborated with the O 1s peak (Figure 2-13). The stick patterns represent WOx and “Free O”,

or more specifically adsorbed O2 from the atmosphere, at 530.5 eV and 531.6 eV, respectively.

At low deposition temperatures, the O 1s peak is an average of the two defined values, but as

deposition temperature increases there is a slight shift in peak position toward predominantly

WOx. The average WOx and free O peak positions are fairly constant throughout the full range of

deposition temperatures with average values of 530.7 ± 0.1 eV and 531.9 ± 0.2 eV, respectively.

Figure 2-14 illustrates the percentage of nitridic (i.e., Nx-W), oxidic (i.e., Ox-W), and

carbidic (i.e. Cx-W), and is representative of the respective percentage occupancy of the sub-peak

under the primary elemental peak. Therefore, not only does the W 4f peak become less saturated

with O signal with increasing deposition temperature, but the available signal is of a lower

oxidation state. The elemental composition of the material deposited from 35 is plotted in Figure

2-15 as function of deposition temperature in the range 100 to 650 °C and compared to

compositions measured also by XPS for films deposited from precursors 33 and 34. The

dominant feature of this comparison is the similarity of composition variation with deposition

temperature among the three precursors. This is not surprising given the similar molecular

structure and apparent common rate-determining decomposition reaction. Another feature is that

the W concentration is relatively constant in the middle temperature range but decreases

significantly at both low and high temperature. This pattern is consistent with a tradeoff for O

and C incorporation at lower and higher deposition temperatures, respectively. At the low

temperature limit, 35 may undergo incomplete decomposition and adventitious O incorporation

61

is competitive. At the high temperature limit, premature and aggressive precursor decomposition

become more significant, as does C incorporation from ligand and solvent decomposition. The N

concentration using 35 was relatively constant (range 6% at 100 °C to 14% at 400 °C).

Figure 2-14. Influence of precursor structure on the percentage of Nx-W, Ox-W, and Cx-W,

according to XPS peak deconvolution.††††

Interestingly, depositions using 35 resulted in the lowest N incorporation, whereas

depositions with 33 provided the most. Additionally, depositions using 33 and 35 provided

†††† Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



62

almost entirely nitridic N (i.e., Nx-W), except for the two lowest deposition temperatures where

there was a presence of CNx at approximately 14% and 17%, respectively. These properties are

unlike depositions with 34, which resulted in a minimum CNx presence of approximately 16%,

with an average of 18 ± 3% below 400 °C and 35 ± 2% above 400 °C. This incorporation was

probably because the formation of diethylamine and N-ethylethanimine during the

decomposition of 34 was much more feasible than from decomposition of 33 and 35. This was

due to the less steric hindrance observed during the hydrogen abstraction by the neighboring

diethylamido group for 34 compared to diisopropylamido group for 35.

Figure 2-15 further shows that C incorporation was nearly identical for all films grown

from 33-35, with integration of C becoming prominent above 450 °C. This was most likely the

result of solvent and/or ligand decomposition. It has been documented that pyridine undergoes

surface catalyzed decomposition at similar temperatures.

Figure 2-14 shows, however, that although qualitatively similar to depositions using 33

and 34, the extent of change in amorphous C incorporation with increasing temperature into the

films was less dramatic when using 34. This result was consistent with C incorporation by ligand

degradation in a surface reaction, which would be hindered by the additional steric bulk of 35.

Oxygen was incorporated into the films by two means: during film growth from

adventitious O2 and H2O or post-growth exposure to air. Due to the relatively low density and

amorphous nature of the films, significant in-diffusion of oxygen was likely. Additionally, at

these low growth temperatures, the sticking probability of gas was high and so any background

O-source can be integrated into the film. The average percentage of WOx below 250 °C was 51 ±

4% and increases steadily to almost 90% at 650 °C. It should be noted that although more of the

incorporated O was Ox-W (Figure 2-14), there was less overall O content in the film (Figure 2-

63

15). The decrease in post-growth O was likely from film densification and C stuffing in the film,

both of which would prevent O in-diffusion.

Deconvolution of the O 1s peaks show that depositions from 34 and 35 experience nearly

identical ratios of free O and Ox-W, where-as films deposited from 33 experienced less Ox-W.

Figure 2-15. Elemental composition for films deposited from 33-35 at various deposition

temperatures, according to XPS. Note differences in concentration scale.‡‡‡‡

‡‡‡‡ Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



64

WNxCy Film Microstructure

Control of the film microstructure was important in diffusion barrier applications. An

amorphous barrier was preferable to a polycrystalline barrier due to the low-energy diffusion

pathways that grain boundaries afford.113 According to GIXD measurements (Figure 2-16), films

deposited from 34 and 35 developed crystallinity at 350 °C and 400 °C, respectively (Figure 2-

16b), whereas films grown from 33 were entirely amorphous for all deposition temperatures.

Films deposited below 350 °C and 400 °C for films grown from 34 and 35, respectively, were

entirely amorphous (Figure 2-16). The primary β-WNxCy (i.e., face-centered-cubic structure)

reflections are expected to result from a solid solution of β-WN0.5 and β-WC0.6, which have

proximal reflections, and for that reason are illustrated as a single reflection. The stick pattern

exists at 37.42, 43.12, 65.52, and 75.22 °2θ for the β-WNxCy (111), β-WNxCy (200), β-WNxCy

(220), and β-WNxCy (311) crystallographic planes, respectively. These powder reflections do, in

fact, coincide with both β-WN0.5 and β-WC0.6 solutions. Similarly, the primary WO3 stick pattern

was an amalgamation of reflections for three common WO3 phases; monoclinic, tetragonal, and

cubic. There are, however, no apparent reflections for any phase of WO3, which should improve

the barrier properties (increased structural disorder).

In both cases there was slight preferential texturing for the β-WNxCy (111) plane,

according to the peak prominence, and therefore its position was used to estimate the lattice

parameter and its full-width-half-max (FWHM) was used to estimate the lower limit of the grain

size, via Scherrer’s equation. The slight discrepancy in peak locations (from the standard) are

expected to be from compositional variations in the film, and not lattice strain, due to the highly

disordered nature of the film as evident in the nanocrystalline domain sizes described in the next

section.

65

Figure 2-16. A) Grazing Incidence X-ray Diffraction (GIXD) patterns taken for films deposited

using compounds 34 and 35. B) Typical crystallographic planes for relevant

materials with respect to their preferred structures and according to their relative

intensities.§§§§

Recall, the XPS data indicate that W was bound to C, N, and O. From that analysis it was

expected that those components belong to either a fully integrated WNxCyOz matrix, separate

interspersed matrices such as WNx, WCx, and WOx, or any permutation in between (e.g., WNxCy

and WOx; WNxOy and WCx; WNx and WCxOy). The crystallographic data obtained using GIXD

(Figure 2-16), suggest that WNx, WCx or the solid solution WNxCy phases exist and adopt a face-

centered-cubic structure. Unfortunately, it cannot be stated with confidence that a separate and

distinct WOx phase exists. The data were consistent with formation of a crystalline β-WNxCy

§§§§ Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



66

core phase surrounded by WNxCyOz solid solution, which forms upon air exposure. Therefore,

the lattice parameter of that crystalline phase should lie around the values of β-WNx or β-WCx.

The lattice constants for β-WC0.6 and β-WN0.5 are 4.236 Å and 4.126 Å, respectively. The lattice

parameters for crystalline films grown with 34 and 35 decrease with increasing deposition

temperature and have maximum values of 4.229 Å and 4.215 Å and minimum values of 4.135 Å

and 4.162 Å, respectively. It was expected that β-WNxCy would produce lattice parameter values

between the endpoints of the solid solution tie line.

It has been shown that lattice constants can increase with deposition temperature as a

result of greater incorporation of C into the lattice. Films deposited from 34 and 35 do in fact

contain greater C levels at higher deposition temperatures, however, it was important to note that

the percentage of Cx-W decreases with increasing temperature. Consequently, a decrease in

lattice constant with respect to the β-WC0.6 lattice constant was seen for films grown from both

34 and 35. This was especially true for films grown with 34, where amorphous C became more

fully integrated.

WNxCy Film Surface Roughness

Highly smooth films are desirable for applications in integrated circuit manufacturing as

they promote interlayer adhesion and minimize electron scattering that increases contact

resistances between layers.80,114 Atomic force microscopy (AFM) measurements were performed

to determine the root-mean-squared (RMS) surface roughness (Figure 2-17). Films deposited

using precursors 33-35 resulted in smooth films that exhibited similar RMS roughness trends at

temperatures below 450 °C. Above 450 °C, the deposits from 34 and 35 continued to increase in

roughness as the films became more crystalline, whereas 33 produced smooth amorphous films

throughout the entire deposition temperature range. The average RMS surface roughness below

150 °C was 0.50 nm, 0.58 nm, and 0.58 nm for films grown from 33, 34, and 35, respectively.

67

These values approached that of the underlying Si substrate (0.18 nm) and are highly desirable.

Between 150-450 °C, the average RMS roughness increased to 2.1 ± 0.4 nm, 1.7 ± 0.7 nm, and

1.3 ± 0.2 nm for films grown with 33, 34, and 35 respectively. The slight roughening of films at

intermediate growth temperatures can be explained by an increase in growth rate, which

promotes the propagation of underlying features more quickly. Additionally, incorporation of

amorphous C has been shown to encourage roughening of the film.

Figure 2-17. Average surface RMS roughness for films deposited from 33-35.*****

WNxCy Film Density Measurements

Films deposited from 33-35 were analyzed with X-ray reflectivity (XRR) to determine

film densities with respect to deposition temperature (Figure 2-18). Film densification occured

for all three precursors with increasing deposition temperature, except at 650 °C. This was

typical of CVD growth as crystallinity is enhanced with temperature due to increased bulk and

surface diffusion rates.81,83 For all three precursors, density decreased at 650 °C when large

***** Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



68

amounts of low density amorphous C (2-3 g/cm3)115 were intermixed with the denser WNxCy

films. Density values for bulk fully crystalline WNxCy have been reported at 15.6 g/cm3, whereas

amorphous WNxCy has been reported between 3-13.1 g/cm3.8,84,85 The slightly smaller density

values for films grown from 33-35 can be attributed to significant O incorporation, which

enhances the disorder in the film and prevents crystal packing, in addition to WOx having a

lower average density (7 g/cm3).86 Regardless, it has been reported that film microstructure was

predominantly responsible for inhibition of Cu diffusion in barrier materials and that density is of

secondary importance for the application.87

Figure 2-18. Correlation between deposition temperature and measured film density for

precursors 33-35.†††††

Films deposited below 650 °C have minimum densities of 4.1 g/cm3, 4.2 g/cm3, and 4.2

g/cm3 for films grown from 33, 34, and 35 respectively. Conversely, maximum film densities

were 6.4 g/cm3, 8.0 g/cm3, and 8.8 g/cm3 when using 33, 34, and 35 respectively. Films from 33

††††† Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



69

were the least dense for all deposition temperatures, which reflect upon their highly amorphous

microstructure, whereas 34 produced the densest films for all temperatures but 450 °C.

Diffusion Barrier Testing

The tests of films grown from 33 and 34 as Cu diffusion barriers have been presented

elsewhere.106,111 The integrity of film grown from 35 as a diffusion barrier is discussed here. Thin

WNxCy films (~5 nm thickness) grown from 35 at 150 °C were evaluated by depositing

approximately 100 nm of Cu onto WNxCy film and annealing the Cu/WNxCy/Si stack at 500 °C

for 30 min under N2.

Figure 2-19. XRD Patterns for as-deposited and post-annealed Cu/WNxCy/Si material

stacks.‡‡‡‡‡

An etch-pit test was performed to evaluate Cu diffusion through the barrier. The etch pit

test has greater sensitivity to Cu diffusion than either 4 Point Probe (4PP) or XRD measurements

(Figure 2-19). Figure 2-20 displays SEM plan-view images of etched films on the post-annealed

Cu/WNxCy/Si stacks (Figure 2-20a and 2-20b), the as-deposited Cu/WNxCy/Si stacks (Figure 2-

‡‡‡‡‡ Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



70

10c), and a failed barrier for comparison (Figure 2-20d). In the event of even small scale Cu

diffusion to the surface, micron-sized inverted pyramidal features (appearing as bright rectangles

in Figure 2-20d) would be visible on the surfaces. The lack of inverted pyramidal features in

Figures 2-20a (lower magnification) and 2-20b (higher magnification) was evidence for

successful barrier performance by films deposited from 35.

Figure 2-20. A) Plan-view image of etch-pit test for post-annealed Cu/WNxCy/Si stack at lower

magnification, B) plan-view image of etch-pit test for post-annealed Cu/WNxCy/Si

stack at higher magnification and C) plan-view image of etch-pit test for as-deposited

Cu/ WNxCy/Si stack, and D) image of failed post-annealed Cu/ WNxCy/Si stack for

comparison purposes.§§§§§

To assess the diffusion barrier tests, XRD and four point probe (4PP) measurements were

first performed. Figure 2-19 illustrates the change in crystallinity between the as-deposited

samples and the post-annealed samples with an annealed Cu/Si structure there to highlight peak

positions for Cu3Si.

§§§§§ Reprinted with permission from Koley, A.; O’Donohue, C. T.; Nolan, M. M.; McClain, K. R.; Bonsu, R. O.;



71

Peaks for Cu (111) and Cu (200) were present at 43.55 and 50.89 °2θ, respectively, for

both as-deposited and post-annealed samples, in addition to a smaller Cu (220) peak at 74.43 °2θ

for the post-annealed sample. Cu (111) is the preferred orientation for barrier applications since

it offers the lowest electrical resistivity and highest electromigration resistance.116 The critical

peaks of Cu3Si (110) and Cu3Si (103) peaks that appeared at 44.77 and 45.35 °2θ, respectively,

in the annealed Cu/Si stack did not appear in either the as-deposited or post-annealed

Cu/WNxCy/Si stacks.

Furthermore, the onset of Cu3Si precipitates can drastically increase the resistivity of the

material stacks upon annealing. The as-deposited and annealed Cu/Si stack had resistivity

measurements of 4.5 ± 0.3 μΩ-cm and 97.3 ± 12.3 μΩ-cm, respectively. In comparison, the

resistivity of the as-deposited and annealed Cu/WNxCy/Si stacks were 5.1 ± 0.2 μΩ-cm and 4.8 ±

0.2 μΩ-cm, respectively. These results were consistent with an intact barrier.

Figure 2-21. HRTEM image clearly showing smooth and distinct boundaries for a post-annealed

Cu/WNxCy/Si sample grown from 35.******

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72

An additional test for barrier evaluation was to examine the interfaces with a high

resolution transmission electron microscope (HRTEM). Figure 2-21 is a cross-sectional HRTEM

image depicting the well-defined interfaces present in a post-annealed Cu/WNxCy/Si sample.

The single crystal lattice structures of the Si substrate and the polycrystalline Cu film are clearly

visible. The amorphous nature of the native Si oxide (SiO2) and WNxCy films is also evident.

Conclusion

By manipulation of reaction conditions, several compounds of the type

WN(NR2)(NRʹ2)(NRʺ

2) were synthesized. Reduced symmetry and increased steric bulk were

associated with improved volatility, an important property for use of the compounds in

conventional CVD or ALD. Compounds 49-52 would be better choice as precursors for ALD

applications and compound 50 would be the best precursor for that application since it sublimes

without decomposition. Complexes 33-47 would be suitable for AACVD given their lower

volatility compared to 49-52 and decomposition during sublimation. The TGA of 35 was

characteristic of sublimation. WNxCy thin films were successfully deposited at temperatures as

low as 100 °C using AACVD from pyridine solutions of 35 (0.051 M). The effect of ligand

structure on film properties has been ascertained. It was determined that 34 and 35 offer more

desirable film properties for diffusion barrier applications in terms of growth rate, surface

roughness, composition, and density. The integrity of thin films deposited from 35 was evaluated

for inhibition of Cu diffusion by 4PP, XRD, SEM etch-pit test, and HRTEM. Cu (~100

nm)/WNxCy (~5 nm)/Si stacks successfully passed annealing at 500 °C for 30 minutes in N2.

Therefore, 35 was identified as a viable single-source precursor for deposition of WNxCy for Cu

diffusion barrier applications.

73

Experimental Section

General Procedures

Unless otherwise specified, all manipulations were performed under an inert atmosphere

(N2, Ar) using standard Schlenk and glovebox techniques. Toluene was purified using an

MBraun MB-SP solvent purification system and stored over activated 3 Å molecular sieves prior

to use. Benzene-d6 was purchased from Cambridge Isotope Laboratories, Inc. and stored over

activated 3 Å molecular sieves (15% w/v) for several days in an inert atmosphere glove box prior

to use. Anhydrous tert-butanol, pentane and redistilled diisopropylamine were purchased from

Sigma-Aldrich and used as received. Hexamethyldisiloxane and pyridine were purchased from

Sigma-Aldrich or Alfa Aesar and stored over activated 3 Å molecular sieves (15% w/v) for

several days in an inert atmosphere glove box prior to use. Compounds 33 and 34 were prepared

as previously described.106,117 All other chemicals were purchased and used as received. 1H and

13C NMR spectra were obtained using Gemini, Mercury, or VXR 300 MHz spectrometers

(Varian shims/probes; Oxford magnets) using the residual protons of the deuterated solvents as

reference peaks. Mass spectra were obtained with a Thermo Scientific Trace GC DSQ mass

spectrometer using the DIP-CI mode of operation or an Agilent 6200 ESI-TOF mass

spectrometer using DART-TOF mode of operation. Elemental analysis results were attained

from Complete Analysis Laboratories, Inc.

Synthesis of WN(NMe2)(NiPr2)2 (35)

In a 100 mL Schlenk flask, 0.50 g (1.5 mmol) of 33 and 10 mL of diisopropylamine (7.2

g, 71 mmol) were combined to give an orange/red suspension. A reflux condenser was attached

and the mixture was brought to a gentle reflux under argon. After 12 h, solvent was removed

from the dark brown solution under vacuum at room temperature. The crude product was

extracted by stirring with hexamethyldisiloxane (50 mL) for 15 min and filtered through Celite.

74

The filter pad was washed with additional hexamethyldisiloxane (2 × 5 mL). The resulting

brown filtrate was concentrated to saturation and left in the glovebox refrigerator (-15 °C)

overnight. The mother liquor was removed, and the product was dried under vacuum to yield

0.40 g (0.90 mmol) of pure 35 as colorless microcrystals (60%). 1H NMR (C6D6, 300 MHz): δ =

1.29 [d, J = 6 Hz, 12 H, -N(CH(CH3)a(CH3)b)2]; 1.37 [d, J = 6 Hz, 12 H, -N(CH(CH3)a(CH3)b)2];

3.37 [s, 6 H, -N(CH3)2]; 3.45 [m, J = 6.4 Hz, 4 H, -N(CH(CH3)a(CH3)b)2]. 13C NMR (C6D6, 75

MHz): δ = 26.2 [-N(CH(CH3)a(CH3)b)2]; 27.2 [-N(CH(CH3)a(CH3)b)2]; 51.4 [-N(CH3)2]; 52.3 [-

N(CH(CH3)a-(CH3)b)2]. DIP-CI-MS: calcd. for [M + H]+ 443.2368; found 443.2364.

C14H34N4W (442.29): calcd. C 38.02, H 7.75, N 12.67; found C 37.89, H 7.68, N 12.63.

Synthesis of WN(NMe2)2(NiPr2) (36)

In a 100 mL Schlenk flask, 0.25 g (0.76 mmol) of 33 and 60 mL of pentane were

combined to create a white slurry. To the slurry, 3.0 mL of diisopropylamine (2.2 g, 21 mmol)

was added to give an orange/red suspension. A reflux condenser was attached and the mixture

was brought to a gentle reflux under argon. After 12 h, the resulting amber/brown solution was

returned to room temperature and solvent was removed under vacuum. The product was


The filter pad was washed with additional hexamethyldisiloxane (2 × 5 mL). The resulting

brown filtrate was concentrated to saturation and left in the glovebox refrigerator (-15 °C)

overnight. The mother liquor was removed, and the product was dried under vacuum to yield

0.19 g (0.49 mmol) of pure 36 as colorless microcrystals (65%). 1H NMR (C6D6, 300 MHz): δ =

1.31 [d, J = 6 Hz, 12 H, -N(CH(CH3)2)2]; 3.35 [s, 12 H, -N(CH3)2]; 3.41 [m, J = 6 Hz, 2 H, - N(-

CH(CH3)2)2]. 13C NMR (C6D6, 75 MHz): δ = 26.4 [-N(CH(CH3)2)2]; 51.3 [-N(CH3)2]; 51.9 [-N-

(CH(CH3)2)2]. DIP-CI-MS: calcd. for [M + H]+ 387.1747; found 387.1750. C10H26N4W

(386.19): calcd. C 31.10, H 6.79, N 14.51; found C 30.93, H 6.83, N 14.43.

75

General Procedure A

In a 100 mL Schlenk flask, 0.25 g (0.76 mmol) of 33 and 60 mL of pentane were

combined to create a white slurry. To the slurry, the amine was added in excess to give an

orange/red suspension. A reflux condenser was attached and the mixture was brought to a gentle

reflux under argon. After 12 h, the resulting amber/brown solution was returned to room

temperature and solvent was removed under vacuum. The product was extracted by stirring with

hexamethyldisiloxane (30 mL) for 15 min and filtered through Celite. The filter pad was washed

with additional hexamethyldisiloxane (2 × 5 mL). Solvent was removed from the filtrate to give

a crude solid. Sublimation of the crude product gave pure product.

Synthesis of WN(NMe2)(NiBu2)2 (39)

Compound 39 was synthesized by General Procedure A. The crude product was purified

by sublimation at 150-250 mTorr and 80-85 °C to afford an orange-white solid. Yield: 60%. 1H

NMR (C6D6, 300 MHz): δ 0.95 [dd, J = 6.3 Hz, 24H, −N(CHaHbCH(CH3)c(CH3)d)]; 1.98 [sp, J =

7 Hz, 4H, −N(CHaHbCH(CH3)c(CH3)d)]; 3.40 [s, 6H, −N(CH3)2]; 3.49 [d, J = 6 Hz, 4H,

−N(CHaHbCH(CH3)c(CH3)d)]; 3.55 [d, J = 6.6 Hz, 4H, −N(CHaHbCH(CH3)c(CH3)d)]. 13C NMR

(C6D6, 75 MHz): δ 20.4 [−N(CHaHbCH(CH3)c(CH3)d)]; 20.7 [−N(CHaHbCH(CH3)c(CH3)d)]; 27.1

[−N(CHaHbCH(CH3)c(CH3)d)]; 52.4 [−N(CH3)2]; 66.5 [−N(CHaHbCH(CH3)c(CH3)d)]. DIP-CI-

MS: calcd for [M + H]+ 497.2970; found 497.2950.

Synthesis of WN(N(CH2)5)3 (40)


by sublimation at 150-250 mTorr and 70-80 °C to afford an orange solid. Yield: 60%. 1H NMR

(C6D6, 300 MHz): 1.39 [m, 6H, -NCH2CH2CH2]; 1.47 [m, J 12H, -NCH2CH2CH2]; 3.80 [t, J =

6 Hz, 12H, -NCH2CH2CH2]; 13C NMR (C6D6, 75 MHz): 25.2 [-N(CH2CH2CH2)]; 29.7 [-

76

N(CH2CH2CH2)]; 60.7 [-N(CH2CH2CH2)]. DIPCI-MS calcd. for [M + H]+ 449.2931; found

449.2934.

Synthesis of WN(N(CH2)6)3 (41)


by sublimation at 150-250 mTorr and 75-85 °C to afford an orange solid. Yield: 55%. 1H NMR

(C6D6, 300 MHz): 1.51 [br m 6H, -NCH2CH2CH2]; 1.75 [br m, 12H, -NCH2CH2CH2]; 3.80 [t,

J = 6 Hz, 12H, -NCH2CH2CH2]; 13C NMR (C6D6, 75 MHz): 26.8 [-N(CH2CH2CH2)]; 33.6

[-N(CH2CH2CH2)]; 61.3 [-N(CH2CH2CH2)]. DIPCI-MS calcd. for [M + H]+ 493.2525; found

493.2513.

General Procedure B

In a 200 mL Schlenk flask, 0.50 g (1.5 mmol) of 33 and 80 mL pentane were combined

to form a white slurry. To the slurry, 6.0 mL of diisopropylamine (4.3 g, 43 mmol) was added to

give an orange/red suspension. A reflux condenser was attached and the mixture was brought to

a gentle reflux under Ar. After 12 h, solvent was removed from the amber/brown solution under

vacuum at room temperature. The residue was extracted by stirring with hexamethyldisiloxane

(50 mL) for 15 min and filtered through Celite. The filter pad was washed with additional

hexamethyldisiloxane (2 × 5 mL). Solvent was removed from the resulting brown filtrate under

vacuum to give crude 36. This was dissolved in pentane (60 mL) and amine was added in excess.

A reflux condenser was attached and the mixture was brought to a gentle reflux under Ar. After

12 h, solvent was removed from the dark brown solution under vacuum at room temperature.

Sublimation of the crude residue afforded pure product.

Synthesis of WN(NEt2)2(NiPr2) (38)

Compound 38 was synthesized by General Procedure C. The crude product was purified

by sublimation at 200-300 mTorr and 60-65 °C to afford light amber microcrystalline powder.

77

Yield 50%. 1H NMR (C6D6, 300 MHz): δ = 1.15 [t, J = 7 Hz, 12 H, -N(CH2CH3)2]; 1.34 [d, J = 6

Hz, 12 H, -N(CH(CH3)2)2]; 3.42 [m, J = 6 Hz, 2 H, -(CH(CH3)2)2]; 3.51-3.72 [m, J = 7 Hz, 8 H,

N(CH2CH3)2]. 13C NMR (C6D6, 75 MHz): δ = 17.6 [-N(CH2CH3)]; 26.6 [-N(CH(CH3)2)2]; 51.2

[-N(CH2CH3)2]; 52.7 [-N(CH(CH3)2)2]. DIP-CI-MS: calcd. for [M + H]+ 443.2373; found

443.2366. C14H34N4W (442.29): calcd. C 38.02, H 7.75, N 12.67; found C 37.79, H 7.71, N

12.58.

Synthesis of WN(N(CH2)5)2(NiPr2) (42)

Compound 42 was synthesized by General Procedure B. The crude product was purified

by sublimation at 150-250 mTorr and 60-70 °C to afford orange-white solid. Yield 50%. 1H

NMR (C6D6, 300 MHz): δ 1.30 [br m, 8H, −NCH2CH2CH2]; 1.40 [d, J = 3 Hz, 12H,

−N(CH(CH3)2)2]; 1.47 [br m, 4H, −NCH2CH2CH2]; 3.44 [m, 2H, −N(CH(CH3)2)2]; 3.80 [t, J = 6

Hz, 12H, −NCH2CH2CH2]. 13C NMR (C6D6, 75 MHz): δ 25.2 [−N(CH(CH3)2)2]; 26.4

[−NCH2CH2CH2]; 29.7 [−NCH2CH2CH2]; 51.0 [−N(CH(CH3)2)2]; 60.7 [−NCH2CH2CH2]. MS

(DART-TOF): calcd for [M + H]+ 467.2368; found 467.2346.

Synthesis of WN(N(CH2)6)2(NiPr2) (43)

Compound 43 was synthesized by General Procedure B. The crude product was purified


NMR (C6D6, 300 MHz): δ 1.36 [dd, J = 24, 6 Hz, 12H, −N(CH(CH3)2)2]; 1.52 [br m, 8H,

−NCH2CH2CH2]; 1.78 [br m, 4H, −NCH2CH2CH2]; 3.47 [m, J = 6 Hz, 2H, −N(CH(CH3)2)2];

3.81 [t, J = 6 Hz, 12H, −NCH2CH2CH2]. 13C NMR (C6D6, 75 MHz): δ 26.4 [−N(CH(CH3)2)2];

26.8 [−NCH2CH2CH2]; 33.5 [−NCH2CH2CH2]; 50.9 [−N(CH(CH3)2)2]; 61.6 [−NCH2CH2CH2].

MS (DART-TOF): calcd for [M + H]+ 495.2681; found 495.2694.

78

General Procedure C

In a 100 mL Schlenk flask, 0.50 g (1.5 mmol) of 33 and 10 mL of diisopropylamine (7.2

g, 71 mmol) were combined to create an orange/red suspension. A reflux condenser was

attached and the mixture was brought to a gentle reflux under Ar. After 12 h, solvent was

removed from the dark brown solution under vacuum at room temperature. The residue was


The filter pad was washed with additional hexamethyldisiloxane (2 × 5 mL). Solvent was

removed from the resulting brown filtrate under vacuum to give crude 35, which was slurried in

excess amine. A reflux condenser was attached and the mixture was brought to a gentle reflux

under Ar. After 6 h, solvent was removed from the dark brown solution under vacuum at room

temperature. Sublimation of the crude residue afforded pure product.

Synthesis of WN(NEt2)(NiPr2)2 (37)


by sublimation at 200-300 mTorr and 55-65 °C to afford light amber microcrystalline powder.

Yield 50%. 1H NMR (C6D6, 300 MHz): δ = 1.15 [t, J = 7 Hz, 6 H, -N(CH2CH3)2]; 1.26 [d, J = 6

Hz, 12 H, -N(CH(CH3)a(CH3)b)2]; 1.33 [br. d, 12 H, -N(CH(CH3)a(CH3)b)2]; 3.46 [m, J = 6 Hz, 4

H, -N(CH(CH3)a(CH3)b)2]; 3.62 [q, J = 7 Hz, 4 H, -N(CH2CH3)2]. 13C NMR (C6D6, 75 MHz): δ

= 17.2 [-N(CH2CH3)]; 26.8 [-N(CH(CH3)a(CH3)b)2]; 51.4 [-N(CH2CH3)2]; 52.7 [-N(CH(CH3)a-

(CH3)b)2]. DIP-CI-MS: calcd. for [M + H]+ 471.2687; found 471.2705. C16H38N4W (470.35):

calcd. C 40.86, H 8.14, N 11.91; found C 40.78, H 7.99, N 11.76.

Synthesis of WN(N(CH2)5)(NiPr2)2 (45)



NMR (C6D6, 300 MHz): δ 1.30 [d, J = 6 Hz, 12H, −N(CH(CH3)a(CH3)b)]; 1.39 [d, J = 6 Hz,

79

12H, −N(CH(CH3)a(CH3)b)]; 1.44–1.49 [m, 6H, −NCH2CH2CH2]; 3.44 [m, J = 6 Hz, 4H,

−N(CH(CH3)a(CH3)b)]; 3.80 [t, J = 6 Hz, 4H, −NCH2CH2CH2]. 13C NMR (C6D6, 75 MHz): δ

25.2 [−N(CH(CH3)a(CH3)b)]; 25.9 [−N(CH(CH3)a(CH3)b)]; 26.6 [−NCH2CH2CH2]; 29.3

[−NCH2CH2CH2]; 51.2 [−N(CH(CH3)a(CH3)b)]; 61.6 [−NCH2CH2CH2]. MS (DART-TOF):

calcd for [M + H]+ 483.2681; found 483.2663.

Synthesis of WN(N(CH2)6)(NiPr2)2 (46)



NMR (C6D6, 300 MHz): δ 1.31 [d, J = 6 Hz, 12H, −N(CH(CH3)a(CH3)b)]; 1.39 [d, J = 6 Hz,

12H, −N(CH(CH3)a(CH3)b)]; 1.52 [br m, 6H, −NCH2CH2CH2]; 1.78 [br m, 6H, NCH2CH2CH2];

3.47 [sp, J = 6 Hz, 4H, −N(CH(CH3)a(CH3)b)]; 3.80 [t, J = 6 Hz, 4H, −NCH2CH2CH2]. 13C NMR

(C6D6, 75 MHz): δ 25.3 [−NCH(CH3)a(CH3)b]; 26.4 [−NCH(CH3)a(CH3)b]; 26.8

[−NCH2CH2CH2]; 33.2 [−NCH2CH2CH2]; 51.1 [−NCH(CH3)a(CH3)b]; 61.6 [−NCH2CH2CH2].

MS (DART-TOF): calcd for [M + H]+ 497.2838; found 497.2861.

General Procedure D

In a 200 mL Schlenk flask, 0.50 g (1.3 mmol) of 36 and 80 mL pentane were combined

to form a white slurry. To the slurry, 8.0 mL of diisobutylamine (5.9 g, 46 mmol) was added to

give an orange/red suspension. A reflux condenser was attached and the mixture was brought to

a gentle reflux under Ar. After 12 h, solvent was removed from the amber/brown solution under

vacuum at room temperature. The residue was extracted by stirring with hexamethyldisiloxane

(50 mL) for 15 min and filtered through Celite. The filter pad was washed with additional

hexamethyldisiloxane (2 × 5 mL). Solvent was removed from the resulting brown filtrate under

vacuum to give the crude product. This was dissolved in pentane (60 mL) and the amine was

added in excess. A reflux condenser was attached and the mixture was brought to a gentle reflux

80

under Ar. After 3 h, solvent was removed from the dark brown solution under vacuum at room

temperature. Sublimation of the crude residue afforded pure product.

Synthesis of WN(NMe2)(NiPr2)(NiBu2) (49)

Compound 49 was synthesized by General Procedure D. The crude product was purified


NMR (C6D6, 300 MHz): δ 0.91 [d, J = 6 Hz, 6H, −NCH2CH(CH3)a(CH3)b]; 0.99 [d, J = 6 Hz,

6H, −NCH2CH(CH3)a(CH3)b]; 1.28 [d, J = 6 Hz, 12H, −N(CH(CH3)a(CH3)b)]; 1.36 [d, J = 6 Hz,

12H, −N(CH(CH3)a(CH3)b)]; 1.97 [sp, J = 6 Hz, 2H, −NCH2CH(CH3)a(CH3)b]; 3.37 [s, 6H,

−N(CH3)2]; 3.43–3.54 [m, J = 6 Hz, 12H, −N(CH(CH3)a(CH3)b), −NCH2CH(CH3)a(CH3)b];)].

13C NMR (C6D6, 75 MHz): δ 20.1 [−NCH2CH(CH3)a(CH3)b]; 20.8 [−NCH2CH(CH3)a(CH3)b];

25.8 [−N(CH(CH3)a(CH3)b)]; 26.7 [−N(CH(CH3)a(CH3)b)]; 27.2 [−NCH2CH(CH3)a(CH3)b]; 51.0

[−N(CH3)2]; 51.9 [−N(CH(CH3)a(CH3)b)]; 66.2 [−NCH2CH(CH3)a(CH3)b]. DIP-CI-MS: calcd for

[M + H]+ 471.2681; found 471.2690.

Synthesis of WN(NEt2)(NiPr2)(NiBu2) (50)




6H, −NCH2CH(CH3)a(CH3)b]; 1.15 [t, J = 6 Hz, 3H, −N(CH2CH3)a(CH2CH3)b]; 1.17 [t, J = 6 Hz,

3H, −N(CH2CH3)a(CH2CH3)b]; 1.31 [d, J = 6 Hz, 6H, −N(CH(CH3)a(CH3)b)]; 1.36 [d, J = 6 Hz,

6H, −N(CH(CH3)a(CH3)b)]; 1.97 [sp, J = 6 Hz, 2H, −NCH2CH(CH3)a(CH3)b]; 3.37–3.67 [m,

10H, −NCH2CH3, −N(CH(CH3)a(CH3)b), −NCH2CH(CH3)a(CH3)b]. 13C NMR (C6D6, 75 MHz): δ

16.5 [−N(CH2(CH3)a)(CH2(CH3)b)]; 16.8 [−N(CH2(CH3)a)(CH2(CH3)b)]; 20.1

[−NCH2CH(CH3)a(CH3)b]; 20.4 [−NCH2CH(CH3)a(CH3)b]; 25.8 [−N(CH(CH3)a(CH3)b)]; 26.3

[−N(CH(CH3)a(CH3)b)]; 27.1 [−NCH2CH(CH3)a(CH3)b]; 50.6 [−N(CH2(CH3)a)(CH2(CH3)b)];

81

52.0 [−N(CH(CH3)a(CH3)b)]; 66.2 [−NCH2CH(CH3)a(CH3)b]. DIP-CI-MS: calcd for [M + H]+

499.2994; found 499.2998.

Synthesis of WN(N(CH2)5)(NiPr2)(NiBu2) (51)



NMR (C6D6, 300 MHz): δ 1.00 [d, J = 6 Hz, 12H, −NCH2CH(CH3)2]; 1.29–1.46 [m, 18H,

−N(CH(CH3)a(CH3)b), −NCH2CH2CH2]; 1.98 [sp, J = 6 Hz, 2H, −NCH2CH(CH3)2]; 3.44 [m, J =

6 Hz, 2H, −N(CH(CH3)a(CH3)b)]; 3.62 [br m, 4H, −NCH2CH(CH3)a(CH3)b]; 3.80 [t, J = 6 Hz,

4H, −NCH2CH2CH2]. 13C NMR (C6D6, 75 MHz): δ 20.4 [−NCH2CH(CH3)a(CH3)b]; 20.8

[−NCH2CH(CH3)a(CH3)b]; 25.0 [−N(CH(CH3)a(CH3)b)]; 25.2 [−N(CH(CH3)a(CH3)b)]; 27.2

[−NCH2CH(CH3)a(CH3)b]; 27.4 [−NCH2CH2CH2]; 33.5 [−NCH2CH2CH2]; 51.1

[−N(CH(CH3)a(CH3)b)]; 60.7 [−NCH2CH2CH2]; 66.5 [−NCH2CH(CH3)a(CH3)b]. MS (DART-

TOF): calcd for [M + H]+ 511.2995; found 511.2995

Synthesis of WN(N(CH2)6)(NiPr2)(NiBu2) (52)




6H, −NCH2CH(CH3)a(CH3)b]; 1.30–1.38 [d, J = 6 Hz, 12H, −N(CH(CH3)a(CH3)b)]; 1.52 [br m,

6H, −NCH2CH2CH2]; 1.78 [br m, 6H, −NCH2CH2CH2]; 1.99 [sp, J = 6 Hz, 2H,

−NCH2CH(CH3)a(CH3)b]; 3.47 [m, 2H, −N(CH(CH3)a(CH3)b)]; 3.60 [br m, 4H,

−NCH2CH(CH3)a(CH3)b]; 3.81 [t, J = 6 Hz, 4H, −NCH2CH2CH2]. 13C NMR (C6D6, 75 MHz): δ

20.3 [−NCH2CH(CH3)a(CH3)b]; 20.8 [−NCH2CH(CH3)a(CH3)b]; 26.4 [−N(CH(CH3)a(CH3)b)];

26.8 [−N(CH(CH3)a(CH3)b)]; 26.9 [−NCH2CH2CH2]; 27.3 [−NCH2CH(CH3)a(CH3)b]; 33.5

82

[−NCH2CH2CH2]; 51.1 [−N(CH(CH3)a(CH3)b)]; 61.6 [−NCH2CH2CH2]; 66.4

[−NCH2CH(CH3)a(CH3)b]. DIP-CI-MS: calcd for [M + H]+ 523.3126; found 523.3127..

Diffusion Barrier Testing

Complex 35 was used to deposit films for testing as a Cu diffusion barrier. A 300 nm of

MOCVD Cu was deposited onto freshly prepared (approximately 5 min of post-growth exposure

to air) WNxCy/Si using (hfac)CuI,II(TMVS). The Cu films were subsequently annealed at a

temperature of 500 °C for 30 min under a flow of 99.999% N2. The annealed Cu/WNxCy/Si

stacks were then analyzed by XRD, SEM, and 4PP. Etch-pit testing was performed by removing

the Cu layer with a dilute nitric acid solution, then removing the barrier with a solution of

NH4OH, H2O2, and H2O in a ratio of 1:1:4 for 10 min, followed by the etching of Cu3Si for 5

seconds with Secco etchant (K2Cr2O7:H2O, 1:1). A schematic is shown in Figure 2-22.

Figure 2-22. A schematic of the etch-pit test.

DFT Calculations

The gas-phase room temperature full optimizations of all molecules were performed

using the DFT functional M06L, as implemented by the Gaussian 09 package.118 Tungsten was

described by the LanL2DZ basis set with additional effective core potential in the LanL2DZ

valence basis. The remaining atoms (N, C and H) were described by the 6-31G* basis set. All

83

geometries were fully optimized without any symmetry restrictions. The ground state (GS) and

intermediate (INT) geometries were optimized as minima, with confirmation by the existence of

zero imaginary frequencies upon calculation of the vibrational frequencies. The optimized

transition states (TS) geometries were identified by the presence of only one negative Eigenvalue

in the Hessian matrix. The thermochemical data (ΔG, ΔH, ΔG‡ and ΔH‡) were obtained within

the rigid-rotator harmonic-oscillation approximation. The optimized structures were visualized

using Chemcraft.119 The Cartesian coordinates for optimized GS, INT and TS structures are

listed in Appendix C (from Table C-1 to Table C-12).

Thermolysis of 35

Compound 35 (0.25 g, 0.565 mmol) was added to a 10 mL round bottom flask attached to

a distillation head, which was then connected to a 10 mL Schlenk flask. Complex 27 was heated

to 300 °C under 1 atm of flowing Ar and all of the gaseous decomposed products from 27 were

trapped in the Schlenk flask at -78 °C (dry ice/acetone). After 4 h, the trapped thermolysis

products were warmed to room temperature and treated with 10 ml of DI water. The solution of

trapped products in DI water was analyzed by GC-EI-MS.

GC-EI-MS was run on a Thermo Scientific Trace DSQ equipped with an EI source, using

a 60 m ATTM-5ms column (Alltech) with a 0.25 mm ID and 0.25 µm film thickness. The

injection port was held at 50 °C, the injection was split 100:1, and 2 µL of sample was injected.

The ion source was held at 150 °C, the EI source was operated at 70 eV and the instrument was

scanned over m/z 25 – 225. Helium was used as the GC carrier gas using a temperature gradient.

The initial temperature was set to 50 °C and held for 2 minutes. The temperature was ramped at

10 °C/minute until it reached 120 °C and held for 1 minute.

84

Crystallographic Structure Determination for 35

X-Ray intensity data were collected at 100 K on a Bruker DUO diffractometer using

MoK radiation ( = 0.71073 Å) and an APEXII CCD area detector. Raw data frames were read

by the program SAINT120 and integrated using 3D profiling algorithms. The resulting data were

reduced to produce hkl reflections and their intensities and estimated standard deviations. The

data were corrected for Lorentz and polarization effects and numerical absorption corrections

were applied based on indexed and measured faces. The structure was solved and refined in

SHELXTL6.1, using full-matrix least-squares refinement. The non-H atoms were refined with

anisotropic thermal parameters and all of the H atoms were calculated in idealized positions and

refined riding on their parent atoms. The asymmetric unit consists of three chemically equivalent

but crystallographically independent complexes. The data were checked for higher symmetry but

none were observed. In the final cycle of refinement, 13145 reflections (of which 11193 are

observed with I > 2(I)) were used to refine 545 parameters and the resulting R1, wR2 and S

(goodness of fit) were 2.14%, 3.77% and 0.980, respectively. The refinement was carried out by

minimizing the wR2 function using F2 rather than F values. R1 is calculated to provide a

reference to the conventional R value but its function is not minimized.

85

CHAPTER 3

CZTSSe: AN OVERVIEW

Photovoltaics

Power consumption around the world has been increasing every day. Currently 15 TW of

energy is consumed globally and most of it comes from fossil fuel. These fuels release a huge

amount of CO2 which contributes to global warming.121 So, an alternative to fossil fuel is

required. Solar derived electricity would help meet new demand and replacement of retiring

fossil fuel plants, contribute to powering our transportation system, and bring affordable

electricity to those who now have none. PV provides clean and renewable energy and also are

easy for installation. Using earth abundant materials for PV makes it economical with respect to

the alternate forms of energy.122,123 Here the advantages and drawbacks of different materials that

are candidates materials in the photovoltaic industry are discussed.

Silicon

Silicon is a very well established and well-studied semiconductor material. Therefore, it

has been the first choice of material for photovoltaic applications. However, the extensive use of

silicon in the semiconductor industry makes obtaining it at a low cost a problem for the

photovoltaic industry.123,124 In order to meet the requirements for both industries, different

production methods have been developed. Usually silicon is produced through the Siemens

process.125 Here polysilicon is deposited through the thermal degradation of trichlorosilane. This

process requires high energy because the deposition is done on high purity silicon slim rods,

which are heated to high temperatures. So, low energy technologies, such as fluidized bed

technology, have been reported.126 Here, silane (SiH4) is introduced into the reactor in the

gaseous form along with silicon seed particles and then the gaseous silane decomposes to form

86

silicon on the seed particles. However, this technology has problems with impurities in the

silicon product.

Kerfless silicon wafers technology has also been introduced to reduce the amount of

silicon lost during the production. A large portion of the silicon is lost as silicon dust during the

wire-saw method. Different new methods have been reported to solve this problem.127,128 The

methods described here are known as edge-defined film-fed growth and string ribbon silicon

technology. Both the methods use molten silicon for wafer production. For edge-defined film-fed

growth a graphite die is used to define thickness of silicon sheets, whereas for ribbon silicon

technology temperature resistant wires are pulled through molten silicon to form ribbon of

silicon. This has reduced the silicon loss during its production. However, these methods were

also found to retain impurities.

Use of ultrathin silicon has been reported to meet the silicon deficiency. It has been found

that a 40 µm film can provide the similar efficiency as 100 µm film.129 This performance is

expected to decrease the amount of silicon required to perform as a photovoltaic material.

Dye-Sensitized Solar Cells

In this method light is absorbed by the dye, which then injects an electron to the

conduction band of a semiconductor material. From here the electron is transported through a

nanoparticle to reach the front contact and perform its work. Once the work is done then it

undergoes a redox cycle to regenerate the dye.130 Efficiency of 10 % was achieved from one of

the ruthenium based dye-sensitized solar cell quite early.131 However over the years there has not

been much improvement in the efficiency of these solar cells.130

Perovskites

Perovskites are solid state sensitized solar cells whose basic technology is based on dye-

sensitized solar cells. Perovskites have a general formula of ABX3 (X = oxygen, carbon,

87

nitrogen, and halogen) where the A cation occupies a cubo-octahedral site and the B cation

occupies an octahedral site. For example, in CH3NH3PbI3, the A cation is CH3NH3+ and the B

cation is Pb2+. This structure has been modified to CH3NH3Pb(IxZ1-x) (where Z is either chlorine

or bromine).

Initially, perovskites were used in solution as sensitizers for dye sensitized solar cells.

Later on the solid perovskites were being used for solar cells. These were found to provide

efficiency as high as 10.9 % using CH3NH3PbI2Cl.132 Recently this efficiency has been improved

to 17.9 %.133 It has been projected that with the fine tuning of the material an efficiency in the

range of 20-30 % can be achieved from this material.134

With the immense potential for perovskites as a photovoltaic material one problem still

remains with it. The use of lead is not at all environment friendly. A replacement with a non-

toxic material is required.

Organic Photovoltaics

Organic Photovoltaics work on the donor acceptor theory. When light is incident on a

material, one of the electrons from the HOMO is transferred to the LUMO of the material. This

creates an electron-hole pair. This pair can reside in one molecule or with neighboring

molecules. The basic design for these molecules involve compounds with extensive conjugation

of electrons and good intermolecular interaction through π-π stacking or hydrogen bonding.135

There are certain advantages and disadvantages of using organic photovoltaics. One of

the advantages for these organic photovoltaic devices is that they are ecofriendly. The

disadvantage is that they still have to achieve high power conversion efficiency. The highest

efficiency obtained through organic photovoltaics is 13.2% for a multijunction cell obtained by

88

Heliatek (manufacturer of organic photovoltaics). Given the diversity of organic molecules there

is a possibility of achieving higher efficiency.

CIGS, CdTe and CZTSSe

CIGS (CuInGaSe), CdTe and CZTSSe (CuZnSnSSe) are known to be excellent

candidates for PV materials.122 Recently CIGS and CdTe have been found to produce cells of

efficiency 21.5 % and 21.4 % respectively.136 CdTe was able to achieve 1 GW production

annually in 2009123 and the same feat was achieved by CIGS in 2011.137,138 However, the global

demands in power consumption are increasing every year. In order to meet the required annual

power production demands (15 TW/year), the amount of PV materials used must be increased to

higher levels.123,137

Figure 3-1. Abundance of photovoltaic elements on earth’s crust.

It is important to understand that neither CIGS nor CdTe are manufactured from earth

abundant elements. Figure 3-1 shows that other than copper none of the elements used for the

formation of CIGS and CdTe are earth abundant.139,140 Also the toxicity of CdTe is a concern.

The necessity for earth abundant, nontoxic PV material can be addressed with CZTSSe

0

50

100

150

200

250

300

350

400

450

Cd Cu Ga In S Se Sn Te Zn

Ab

un

dan

ce (

pp

m)

Elements

89

(Kesterite) because it has a band gap similar to CIGS and is composed mostly of earth abundant

(Figure 3-1) and nontoxic elements.122,137 Recently CZTSSe has been reported to provide films

with high efficiency (above 12 %) which makes it a strong competitor for next generation PV

material as compared to CIGS and CdTe.141,142

Deposition of CZTSSe

Different deposition techniques have been applied for the deposition of CZTSSe.

Currently the drawback for CZTSSe is the low efficiency compared to CIGS and CdTe. The

following discussion will provide a short comparative overview between deposition methods and

efficiency achieved from the resulting films.

Sputtering

Sputtering is a vacuum deposition procedure where the target materials are bombarded

with highly energized ions. One of the first deposition of CZTS films was conducted through

sputtering. The resulting material was reported as a candidate for photovoltaics due to its optimal

band gap.143 CZTSSe films of efficiency 5.2 % were obtained by sputtering of metal precursors

followed by sulfo-selenization.144 Films with efficiency around 6.7 % were obtained145 as an

improvement from previous depositions146 due to preferential etching techniques of CZTS

absorber layers. Co-sputtering of different chalcogenides followed by annealing with SnS(g) and

S2(g) resulted in 8 % efficient films.147 Manipulating the SeS2/S weight ratio during the

annealing process of film deposition through sputtering resulted in high efficiency of 12.3 %.148

Co-evaporation

In co-evaporation method multiple precursors are heated thermally under vacuum to

volatilize them followed by deposition on the substrate. Here the precursors must be volatile

enough to be transported to the vapor phase. An advantage to this technique is that the film

composition can be tuned easily by changing the proportions of precursors used. An increase in

90

efficiency from 0.02 % to 5.4 % was observed when the CZTS films were annealed with SnS(g)

and sulfur instead of just sulfur.149 This was attributed to the fact that during the deposition

process of CZTS, a significant amount of Sn was lost. The Sn was then replaced by annealing the

films with SnS(g). A slight improvement of efficiency was observed when Cu2ZnSnSe4 films

produced through co-evaporation showed power conversion efficiency of 9.15 %150 with respect

to 8.4 % for Cu2ZnSnS4.151

Pure Solution

In pure solution deposition, the precursors are dissolved in a solvent and deposited

through a sol-gel method. ITO has been prepared from a solution of SnCl2•2H2O and

alcohol.152,153 Although very economical, one of the disadvantages of this method is that there is

possible contamination from solvents into the films. Films from copper (II) acetate monohydrate,

zinc (II) acetate dihydrate and tin (II) chloride dihydrate with band gap of 1.49 eV showed the

potential for this method in the PV industry.154 However the films showed efficiency lower than

6 % which was much lower with respect to efficiency achieved through other methods.155-160

Recently, higher efficiency has been achieved through spray deposition of water-ethanol based

colloidal inks which has resulted in 8.6 % efficiency161 which increases to 10.8 % on fine tuning

the Sn content in the films.162

Nanoparticle Based Deposition

To avoid the impurities from the solution based approach, nanoparticles of composition

closer to the required material were dissolved in a solution and used for deposition. This method

was based on the concept that the required composition would be achieved with minimum

foreign material from solvents. Initially a 7.2 % efficient CZTSSe film,163 and then a 6.8 %

efficient CZTSSe film doped with germanium were prepared through this process.164 Using

binary and ternary sulfide nanoparticles followed by annealing with selenium resulted in an

91

increase in efficiency to 8.5 % for CZTSSe films.165 By controlling the spatial distribution of

elements specially towards the surface ( Sn rich) of the CZTS material an efficiency of 8.6 %

was achieved.

Particle-Solution Deposition

In this method both particles and solutions of precursors are combined and then spin

coated on a surface. Since it uses a combination of solution and solid particles together it usually

generates a thicker mixture that results in the formation of large grain boundaries as seen in

CIGSSe.166 This method has resulted in the formation of CZTSSe films producing highest

efficiencies. Initially a 10.1 % efficiency was observed from the CZTSSe films167 followed by an

improvement to 11.1 %,168 and recently 12.6 % efficiency was achieved which is the highest

obtained for CZTSSe material.141

There has been a significant development for the earth abundant material CZTSSe in the

past few years compared to other photovoltaic materials.136 However, the maximum efficiency

achieved is still lower than CIGS and CdTe. In order to improve the efficiency, it is important to

understand the thermochemistry of CZTSSe along with the development of new deposition

methods.

Computational Study

Several computational studies have been done on the CZTSSe in order to understand its

structural, electronic and vibrational properties of the material. Some of them have been

compared with the experimental data when possible. Given the complexity of the material,

theoretical calculations have been limited.

Initially, a study of the band gap optimization was done both theoretically (DFT using

PW91)169 and experimentally (UV-Vis absorption spectra). Here, it was observed that the band

92

gap can be tuned by changing the ratio of Se/(S+Se). Although the trends were similar for both

theoretical and experimental methods, the exact value for the exact band gap varied by 1.0 ev.170

To understand the composition dependence of the structural and electronic properties of

CZTSSe density functional HSE was used.171 Here it was stated that increasing the Se content of

the films decreases the band gap of the film. It was also reported that high efficiency was

obtained from those CZTSSe films whose compositions had high Se content in the films.

Figure 3-2. Conventional unit cells for Kesterite structures.††††††

Another DFT study using the PBE functional indicated that changing the anion

distribution along with the S/Se ratio affects the band gap.172 These studies were performed using

†††††† Reprinted with permission from Khare, A.; Himmetoglu, B.; Cococcioni, M.; Aydil, E. S. J. Appl. Phys. 2012,

111, 123704-1-123704-8.

93

different compositions of CZTSSe (Figure 3-2). Raman studies were also performed using DFT,

which provided results that were on par with the experimental values. A DFT study using the

VASP code was performed in order to understand the cation disorder in the CZTSSe material.173

To understand the diffusion of elements of PV materials (CIGSe and CZTSSE) in the

CdS buffer layer, a computational study was conducted. This study was done using the DFT

functional HSE06 and PAW approach as implemented in the VASP code.174

All the calculations presented here have been performed on the solid state CZTSSe

material. The thermochemistry of the gas phase species, which are in equilibrium with the

CZTSSe material, has not been investigated. This study would provide information about the

different chemical species that are likely to be in the gas phase during the active operation of

CZTSSe as a photovoltaic material.

94

CHAPTER 4


Computational Methods

The goal of this study is predicting the thermodynamics for formation of stable binary

and ternary vapor phase species by Density Functional Theory (DFT) calculations on the

reaction equilibria for formation of certain components of CZTSSe as independent species. Of

particular interest are the nature and possible formation of different metal sulfides, metal

selenides and metal clusters under condition of high temperature degradation of the CZTSSe

composite material. Results from DFT calculations on sulfur allotropes were verified against

CALPHAD data, which also provided access for modelling energetics of condensed phases that

are difficult to derive by DFT. The DFT calculations for each equilibrium system were

performed using two separate Density Functionals B3LYP and M06L, and results from both are

presented. Implementation of the diffuse functionality and the effective core potential (ECP)

were carried out to afford accurate prediction of gas phase energetics involving both main group

and transition metals.

DFT calculations have been done for all possible binary species that can be formed from

CZTSSe. The calculations were used to identify the stable binary molecules which have higher

possibilities of formation among all the different molecules. Therefore, initially some

calculations were done on metal sulfides and selenides as a benchmark and compared with the

SGTE database. SGTE is engaged in critical assessment and compilation of thermodynamic data

for inorganic and metallurgical substances. The method that gave the closest value to the

database was used to do the calculations to complete the database.

95

All possible species were assumed to be in the gas phase. The DFT calculations yielded

thermochemical data at 298.15 K and 1 atm pressure unless otherwise mentioned. The main

objective is to calculate the following for each species:

a) Total Enthalpy

b) Total Free Energy

c) Bond Length

d) Bond Angle (where applicable)

e) Optimized Geometry

The Enthalpy of Formation (ΔH°f) and the Free Energy of Formation (ΔG°

f) were used to

determine which molecules would have the possibility of being present in the gas phase at a

particular temperature and pressure. Bond lengths and the bond angles provided insight into the

nature of the bonding in the molecules.

For non-metals, B3LYP/6-31G* has been used as it applies to all the elements from H to

Kr and also has been used in the literature to give data comparable to the experimental values.175

For molecules containing both metal and non-metal atoms, M06L and B3LYP functionals have

both been used for calculations. In the past, the M06L functional has been found to give accurate

results for organometallic compounds.176-179 The three different metals that will be studied are

copper, zinc and tin, hence the basis set LANL2DZ should serve the purpose for both the metals

and the sulfur.179,180

Equations 4-1 and 4-2 were used to calculate the ΔH°f and ΔG°

f.

ΔH°f(MxSy) = ΔH°

f(MxSy) – x ΔH°f(M) – y ΔH°

f(S) (4-1)

ΔG°f(MxSy) = ΔG°

f(MxSy) – x ΔG°f(M) – y ΔG°

f(S) (4-2)

96

Sulfur Allotropes

Sulfur is known to exist in different allotropic forms S1-8. Therefore, it is important to

optimize each one of them separately with B3LYP/6-31G* to determine the most stable one in

the gas phase and use it for other calculations. Among all the sulfur allotropes, S4 is known to

exist in eight different structural forms (Table 4-1) of which first six are singlet molecules and

the last two are triplet. Initial calculations were done for all the eight S4 structures to obtain the

one with minimum energy, which later would be compared with the different sulfur allotropes.

Table 4-1. DFT calculations for S4 (B3LYP/6-31G*) and comparison with literaturea.

Species

(Symmetry)

Spin

State Structure

ΔH°f

(report

ed)

ΔG°f

(reporte

d)

Ref. for

Reported

Value

ΔH°f

(calculat

ed)

ΔG°f

(calcul

ated)

S4(C

2v)

Singlet

0.0 4.9 183 0.0 -96.2

S4(C

2h)

Singlet

41.9 40.3 183 29.2 -66.6

S4(D

2h)

Singlet

5.6 8.2 183 89.2 -2.4

S4(C

s)

Singlet

61.6 61.0 183 73.8 -21.2

S4(D

2d)

Singlet

79.6 84.0 183 88.8 -4.42

S4(D

3h)

Singlet

106.6 111.3 183 113.9 -22.0

S4(C

2v)

Triplet

50.1 43.0 183 1.8 -102.3

S4(C

2h)

Triplet

88.2 73.7 183 15.2 -89.0

aAll values in kJ/mol

97

Ab initio calculations (G3X(MP2) level) have also been done on all the different S4

structural moieties.181 All the calculations obtained through DFT are based on gas phase species

similar to those obtained in ab initio data, so both computational methods should identify the

same structure as the most stable one. The results have been compared in Table 4-1. The first six

entries are all singlet species and the last two, S4(C

2v) and S

4(C

2h) are in triplet state.

All the values entered in Table 4-1 are with respect to the enthalpy value of S4(C2v) in the

singlet form. DFT calculations give S4(C2v) in the triplet form as the most stable moiety while

the ab initio literature results181 suggests that S4(C2v) in the singlet form is the most stable

structure. DFT value for the enthalpy of formation of S4(C2v) in the singlet state was more

comparable to the reported value than in the triplet state. Ab initio has been known to handle spin

states correctly in the past.182,183 All other sulfur allotropes except S2 would be calculated in

singlet form hence it was decided to compare the singlet form for the final comparison.

The optimized structural parameters for the allotropes of sulfur are represented in Table

4-2. All the enthalpy and free energy values are calculated with respect to that of sulfur atom and

the values give the energy difference per sulfur atom for each allotrope. S7 has shown an

interesting result that it exists as a combination of two S2 and one S3 moiety interacting with each

other. The bond lengths for S7 as mentioned in Table 4-2 indicates that there is definitely an

interaction.

It is widely known that S8 is the most stable isotope in the solid form and it was also

found to be the most stable one among all the different allotropes in the gas phase. Although all

the calculations were done under 1 atm pressure and 298.15 K, S8 was also found to optimize in

the crown form similar to that in the solid state. The calculations were repeated at high

98

temperatures for S8 along with all other calculations for metal sulfides, selenides and metal

clusters. For all calculations at 298.15 K and 1 atm pressure, S8 was used as a source of sulfur.

Table 4-2. Calculations for allotropes of sulfur (B3LYP/6-31G*)

Species Structure

Bond

Length (Å)a

Bond

Length (Å)b

Bond

Angle (º)

ΔH

(kcal mol-1)

ΔG

(kcal mol-1)

S S 0.0 0.0

S2 S=S 1.93 1.89 -400.8 -372.8

S3 1.95 1.91 118.3 -595.4 -533.5

S4

1.94, 2.20 105.7 -825.9 -730.1

S5

2.06

100.3,

91.1

-257.4 -1077.0

S6

2.11 103.1 -1348.5 -1171.9

S7

2.04, 2.17,

2.33

1.99,2.18

110.3,

103.1,

106.9

-1574.8 -1368.6

S8

2.10 2.05 109.1 -1852.3 -1601.6

aDFT results breported values184,185

The results obtained for the allotropes of sulfur through DFT were compared with the

values obtained through Thermocalc (a program used for the preparation of the SGTE database)

to determine whether both follow the same trend in energy values. Figure 4-1 represents a

comparison graph of the Gibbs free energy data for all allotropes with respect to the sulfur atom

between DFT and Thermocalc. The graph shows that both methods of calculation give the same

99

trend of Gibbs free energy. This comparison was done as a proof of concept study to confirm that

results from both methods follow the same trend for known molecules, before calculating

unknown species by DFT.

Figure 4-1. Comparison between Thermocalc and DFT data for sulfur allotropes.

Metal Sulfides

In order to calculate ΔH°f and ΔG°

f for the metal sulfides from equations (4-1) and (4-2)

optimization was done for the sulfides and the metals separately at STP. The sulfides chosen for

this purpose were CuS, Cu2S, ZnS, SnS and SnS2. Among these sulfides CuS, ZnS and SnS are

linear structures hence their optimization did not change their geometry. When Cu2S was

optimized it was expected to give a bent structure. However, it resulted in a three membered ring

(Figure 4-2). Conversely, SnS2 optimized to a linear structure like CO2.

Calculations were done with the two different density functionals, B3LYP and M06L

because when Cu2S was optimized with M06L, and ZnS was optimized with B3LYP, then they

provided results which were more comparable data with the SGTE database than when

-60

-50

-40

-30

-20

-10

0

0 2 4 6 8 10

En

ergy(k

Cal/

mol

ato

m)

Number of S atoms

Gibbs Energy (ΔG0f)of S Species

Thermocalc

DFT

100

optimized with B3LYP and M06L respectively. Therefore, both density functionals were used

for calculations and comparisons. The basis set LANL2DZ was used for all calculations. Since

only one basis set has been used for all calculations from here onwards the two DFT methods

will be differentiated by their density functionals as B3LYP and M06L.

Figure 4-2. Optimized structures for Cu2S (M06L/LANL2DZ) and SnS2 (B3LYP/LANL2DZ).

Table 4-3. Comparison of enthalpy, entropy, and Gibbs energy of formation of gaseous species

at 298.15 K.a

Species CuS SnS ZnS Cu2S SnS2

ΔH: SGTE -6143 -101375 30901 -229553 -58951

ΔH: B3LYP -41659 -129372 37263 -110113 -81922

ΔH: M06L -99276 -156153 -55599 -198972 -108244

ΔS: SGTE 12.230 10.515 11.495 -128.875 0.147

ΔS: B3LYP 9.128 4.213 8.426 -26.681 -14.979

ΔS: M06L 6.683 3.249 7.097 -31.333 1.569

ΔG: SGTE -9790 -104510 27474 -191129 -58995

ΔG: B3LYP -44380 -130628 34750 -102158 -77456

ΔG: M06L -101268 -157122 -57715 -189630 -108 712

aThe units are J/mole-atom for ΔH, ΔG and J/mole-atom/K for ΔS.

101

Results obtained from these calculations were compared with the values from the SGTE

database. Comparisons were done for three different temperatures: 298.15 K, 670 K and 3000K.

The values available in the SGTE database were at 670 K, so this temperature could be used for

benchmarking. To obtain values for a wide range of temperatures, calculations were compared at

298.15 K and 3000 K.


at 670.00 K.a


ΔH: SGTE -6744 -103303 30836 -237363 -59991

ΔH: B3LYP -42858 -130682 36030 -110958 -82963

ΔH: M06L -56118 -134279 158646 -141501 -86391

ΔS: SGTE 11.008 6.573 11.018 -145.827 -1.929

ΔS: B3LYP 6.190 1.004 5.943 -147.905 -17.267

ΔS: M06L -130.752 -136.355 -127.966 -148.208 -117.031

ΔG: SGTE -14119 -107707 23454 -139659 -58698

ΔG: B3LYP -47006 -131355 32049 -11862 -71394

ΔG: M06L 31486 -42921 244383 -42202 -7980


At 298.15 K, the calculations (Table 4-3) show that all metal sulfides except ZnS have a

possibility of existence in the gas phase. Based on the Gibbs free energy data (Table 4-3), both

M06L and the SGTE data indicate that among all the metal sulfides Cu2S is the most stable one

at 298.15 K in gas phase. However, B3LYP obtains SnS as the most stable species at 298.15 K.

Free energy values of Cu2S obtained through SGTE and M06L are extremely close whereas the

102

values obtained for SnS vary widely for all three systems. B3LYP and SGTE indicate that ZnS

should not be present in the gas phase at 298.15 K. However, M06L indicates the opposite. This

indicates that ZnS gives better results with B3LYP than with M06L.

A similar trend is followed at 670.0 K as shown in Table 4-4. None of the calculated

values for ZnS showed favorable existence in the gas phase at 670.0 K. CuS also gave positive

Gibbs free energy of formation value when calculated using M06L functional. However, results

obtained using B3LYP and SGTE provide a negative value and their values are close to each

other even at 298.15 K. So for CuS, B3LYP functional is a comparable mode of calculation for

the gas phase species. Calculated values for SnS2 obtained using B3LYP functional were found

to be more comparable with the SGTE calculated values than when M06L functional was used.


at 3000.00 K.a


ΔH: SGTE -13450 -121519 32421 -289816 -71571

ΔH: B3LYP -49999 -137863 28660 -115757 -89398

ΔH: M06L -63430 -141514 136908 -146398 -92947

ΔS: SGTE 6.583 -5.924 13.312 -179.187 -10.137

ΔS: B3LYP 1.325 -3.905 1.046 -26.592 -21.710

ΔS: M06L 0.504 -4.016 -4.851 -34.554 -25.489

ΔG: SGTE -33200 -107747 -7515 247744 -41571

ΔG: B3LYP -53974 -126148 25522 -35982 -24267

ΔG: M06L -64942 -129465 151461 -42736 -16480


Most of the calculated values obtained at 3000 K (Table 4-5) follow the same trend as at

298.15 K and 670.0 K. The SGTE values indicate that ZnS has a negative free energy of

formation whereas both the DFT results indicate the opposite. These results from SGTE are

103

contrasting to the values from previous temperatures. If ZnS is not bound at 670.0 K, then it will

also not be bound at 3000.0 K. Cu2S results at 3000.0 K were different in SGTE, B3LYP and

M06L. Cu2S is known to decompose at 1398 K.186 So SGTE results are probably more accurate

at this high temperature for the solid Cu2S. The negative Gibbs free energy values obtained using

both B3LYP and M06L indicates that at high temperatures Cu2S is expected to be in the gas

species with minimum intermolecular interaction. Comparing all three temperature ranges it can

be said that the B3LYP functional is more comparable with the SGTE database with most

sulfides except for Cu2S at 298.15 K and 670.0 K, where the results are similar to M06L system.

Figure 4-3 indicates that CuS, SnS2 and SnS follow a linear trend for the enthalpy of

formation values for both B3LYP and M06L. At 298.15 K results obtained using B3LYP for all

the metal sulfides except Cu2S were closer to the SGTE values. Cu2S produced comparable

values at 298.15 K when optimized using M06L. Results obtained for ZnS using B3LYP are

closer to the SGTE values. At 670.0 K and 3000.0 K SnS, SnS2 and CuS produced similar trends

and closer values. Results for Cu2S follow the trend using M06L system at room temperature but

not at higher temperatures.

Figure 4-4 shows a similar trend in the entropy of formation for all metal sulfides except

Cu2S at temperatures 298.15 K and 3000.0 K. The entropy of formation should be negative

which was found with both SGTE and DFT. This is mainly because of the decreasing number of

molecules during the formation of these metal sulfides. The structure for SnS2 (Figure 4-2) was

found to be linear whereas the structure for Cu2S (Figure 4-2) was found to be triangular like

cyclopropane. SnS2 has a structure similar to the diatomic metal sulfides which is why all these

molecules except Cu2S have comparable values for ΔS0f as shown in Figure 4-4. The bending

modes of vibration seen for SnS2 would not be seen for the other diatomic molecules. This could

104

be the reason behind the SnS2 values to be slightly different from the other diatomic molecules.

At 670.0 K B3LYP results for all metal sulfides except Cu2S showed comparable results with the

SGTE database. However, values obtained using M06L for all other metal sulfides deviated from

the linear trend. Results at 3000.0 K and 298.15K were similar.

Figure 4-3. Enthalpy of formation of gaseous species as calculated from the SGTE SSUB4


3000.00 K.

105

Figure 4-4. Entropy of formation of gaseous species as calculated from the SGTE SSUB4


3000.00 K.

The Gibbs free energy trend shown in Figure 4-5 indicates similar values from both

B3LYP and M06L for all metal sulfides at 298.15 K and 670.0 K except the results for ZnS

using M06L at 670.0 K. At 3000.0 K the values for SnS, SnS2 and CuS followed the same trend

as SGTE. Results for ZnS using B3LYP were comparable and follow the same trend. However,

results for ZnS from M06L and the values for Cu2S using both B3LYP and M06L deviated

completely from the SGTE trend. One of the reason for these differences in the results could be

106

from the fact that in DFT all the calculated energies correspond to a single molecule formation

with no intermolecular interaction. A lot of the values in the database are obtained

experimentally, which includes intermolecular interaction.

Figure 4-5. Gibbs energy of formation of gaseous species as calculated from the SGTE SSUB4


3000.00 K.

To summarize for the metal sulfides, results from different DFT functionals are closer

with the SGTE values at different temperatures. Based on the metal a particular DFT function

107

can be chosen to calculate the gas phase thermochemical data for a species whose data is not

available in the database. Except Cu2S all other metal sulfides were found to give results from

B3LYP that were closer to the SGTE values. The only distinction of Cu2S with other metal

sulfides was that it has two transition metals in its structure. M06L works excellently with the

transition metals, so it is possible that having two transition metals in Cu2S makes it difficult for

B3LYP to optimize.

Metal Selenides

Calculations for metal selenides were performed based on Equations 4-1 and 4-2, similar

to the metal sulfides. Among the several allotropes of selenium187 Se8, one of the stable

allotropes of selenium was used for calculations maintaining the consistency with the sulfur

allotrope. The density functionals M06L, B3LYP have been used with the basis set LANL2DZ

for comparison, given the preliminary success with metal sulfides. Calculations were done at

temperatures 298.15 K and 3000.0 K. Calculated energy values for the formation of metal

selenides in gas phase as single species are shown below. A comparison between values from

two different DFT functionals is performed.

A) B)

Figure 4-6. Optimized geometry for SnSe2 with B3LYP (A) and M06L(B)

Cu2Se optimized to a geometry similar to Cu2S, with the Cu-Se bond length found to be

about 2.3 Å in Cu2Se with respect to 2.18 Å in Cu2S. However, SnSe2 optimized in two different

108

geometries, bent for B3LYP and linear for M06L (Figure 4-6) at all temperatures when started

with the bent structure (Figure 4-6 A). All other metal selenides optimized to a linear structure

like their sulfide analogues.


at 298.15 K.a

Species CuSe SnSe ZnSe Cu2Se SnSe2

ΔH: B3LYP -45.80 -124.55 36.10 -110.90 -81.77

ΔH: M06L -58.65 -127.10 134.25 -140.93 -90.63

ΔH: SGTE -19.69 -99.99 43.83 -104.90 n.a.

ΔS: B3LYP 0.008 0.003 0.008 -0.027 -0.036

ΔS: M06L 0.005 0.001 0.007 -0.031 -0.0015

ΔS: SGTE 0.010 0.014 0.012 -0.029 n.a.

ΔG: B3LYP -48.30 -125.50 33.65 -102.83 -111.90

ΔG: M06L -60.30 -127.35 132.05 -131.63 -135.40

ΔG: SGTE -22.81 -104.17 40.26 -96.09 n.a aThe units are kJ/mol-atom for ΔH, ΔG and kJ/mol-atom.K for ΔS.

Results from both functionals and SGTE in Table 4-6 indicate that all the metal selenides

except ZnSe can be present in the gas phase. Both the Gibbs energy of formation and enthalpy of

formation values calculated using density functionals B3LYP and M06L were highly positive,

along with the SGTE values indicating that formation of ZnSe in gas phase at 298.15 K is

energetically disfavored. Based on the Gibbs free energy values obtained using B3LYP, SnSe is

the most stable species followed by SnSe2, Cu2Se, and CuSe, whereas for M06L SnSe2 was

found to be more stable than SnSe followed by Cu2Se and CuSe. There are no data available for

SnSe2 in the SGTE database. Without SnSe2 the trend for increasing Gibbs free energy in SGTE

was similar to that obtained from B3LYP.

Table 4-7 indicated that all the metal selenides except ZnSe have a possibility of

formation in the gas phase. However, B3LYP calculations for SnSe2 indicate that its formation at

3000.0 K is both energetically and entropically disfavored whereas M06L values suggest that it

109

can exist in the gas phase at 3000.00 K. The trend of the different metal selenide species (except

SnSe2) arranged in ascending order of their Gibbs free energy value was found to be same for

values obtained in DFT (B3LYP and M06L) and SGTE. The values indicated that SnSe was the

most stable species followed by CuSe, Cu2Se and ZnSe. This order was different with respect to

the trend seen at 298.15 K. At 298.15 K Cu2Se was found to be more stable than CuSe. The

decrease in the value of Cu2Se with respect to CuSe could be attributed to the high negative

entropy value for the former with respect to the latter. This is due to the higher decrease in the

number of molecules for the formation of Cu2Se than CuSe. At 3000.00 K TΔS value is much

higher than at 298.15 K which results in the low Gibbs free energy value for Cu2Se than CuSe.


at 3000.00 K.a

Species CuSe SnSe ZnSe Cu2Se SnSe2

ΔH: B3LYP -54.30 -133.10 27.60 -116.63 -89.37

ΔH: M06L -67.20 -135.60 117.90 -146.70 -98.17

ΔH: SGTE -26.30 -119.60 35.40 -112.30 n.a.

ΔS: B3LYP 0.001 -0.004 0.001 -0.032 -0.031

ΔS: M06L -0.002 -0.006 -0.009 -0.036 -0.008

ΔS: SGTE 0.005 -0.002 0.005 -0.0353 n.a.

ΔG: B3LYP -57.30 -120.60 24.80 -20.50 2.40

ΔG: M06L -61.45 -115.95 144.60 -38.20 -75.27

ΔG: SGTE -42.30 -113.40 21.10 -6.40 n.a. aThe units are kJ/mol-atom for ΔH, ΔG and kJ/mol-atom.K for ΔS.

Figure 4-7 indicates that the enthalpy of formation values obtained for CuSe, Cu2Se and

SnSe from B3LYP and M06L functional are closer to the values obtained from the SGTE

database. Similar to ZnS the values obtained for ZnSe using B3LYP functional were closer to the

values from the SGTE database than the values obtained using M06L. Cu2Se values obtained

using both B3LYP and M06L were similar to the SGTE database results unlike CuS which

provided closer results with M06L.

110

Figure 4-7. Enthalpy of formation of gaseous species as calculated from the SGTE SSUB4

database compared to the energies calculated from DFT at 298.15 and 3000.00 K

Entropy of formation values for CuSe, SnSe and ZnSe (Figure 4-8) were found to be

close to 0 J/mol-atom.K similar to that found for their corresponding sulfide species (Figure 4-4).

Similar to Cu2S (Figure 4-4) values obtained for Cu2Se (Figure 4-8) were lower than the other

metal selenides and this is probably due to the larger decrease in the number of molecules during

the formation of Cu2Se. At 3000.00 K the results for Cu2Se from M06L functional were closer to

the SGTE database than those from B3LYP.

Figure 4-8. Entropy of formation of gaseous species as calculated from the SGTE SSUB4

database compared to the energies calculated from DFT at 298.15 and 3000.00 K.

111

Figure 4-9. Gibbs free energy of formation of gaseous species as calculated from the SGTE

SSUB4 database compared to the energies calculated from DFT at 298.15 and

3000.00 K

Gibbs free energy of formation values of CuSe, SnSe and Cu2Se obtained from B3LYP

and M06L functionals were similar to those obtained using SGTE database. Results obtained for

ZnSe (Figure 4-9) using B3LYP functional were closer to the SGTE database compared to the

results obtained using M06L, which is a similar trend as observed for ZnS (Figure 4-6). The

Gibbs free energy values for the metal selenides obtained using B3LYP and M06L at both

298.15 K and 3000.00 K were closer to the SGTE database (Figure 4-9) with respect to the

values obtained for metal sulfides (Figure 4-6).

To summarize, for the metal selenides both the DFT functionals give similar results

compared to the SGTE database. Both DFT and SGTE values give different trends at the two

temperatures. Currently the SGTE database does not have thermodynamic data for the SnSe2 in

gas phase for comparison purposes.

Bimetallic and Tetrametallic Clusters from Copper, Zinc and Tin

The next calculations were performed on the different clusters that are possible from

copper, zinc and tin to find their possibility of existence in gas phase at room temperature. In the

112

beginning simple clusters (clusters containing two different metals) were used for calculations.

DFT functionals M06L and B3LYP combined with basis set LANL2DZ were used for

calculations. Along with diatomic CuZn and CuSn, Cu2Zn optimized as a linear structure.

A) B)

C)

Figure 4-10. Optimized structures for Cu3Sn (A-M06L/LANL2DZ, B-B3LYP/LANL2DZ) and

Cu3Zn (C).

Tetrametallic clusters optimized to give a different structures for both Cu3Sn and Cu3Zn.

Cu3Sn optimized in two different structures from the two different functionals as shown in

Figure 4-10 (A and B). The structure for Cu3Sn as shown in Figure 4-10 (B) is similar to a

tetrahedron moiety reported in literature where the Cu3Sn assumes a tetrahedral structure.188

Cu3Zn optimized to a trigonal planar structure (Figure 4-10 C) irrespective of the functional.

However, the structure obtained for Cu3Zn was also found to be a tetrahedron in literature.189

Table 4-8 indicates all the metal clusters have a possibility of being present in the gas

phase. The negative entropy value could be attributed to the fact that these clusters are formed

from the respective metals in their atomic state in gas phase. This leads to a decrease in the

113

number of entities during the formation of clusters. The Gibbs free energy trend indicates that

Cu3Sn is the most stable species at room temperature.


at 298.15 K.a

Species CuZn Cu2Zn CuSn Cu3Sn Cu3Zn

ΔH: B3LYP -49.9 -218.6 -178.8 -511.7 -315.0

ΔH: M06L -76.8 -295.4 -206.8 -746.7 -460.6

ΔS: B3LYP -0.068 -0.222 -0.080 -0.269 -0.263

ΔS: M06L -0.069 -0.233 -0.081 -0.314 -0.269

ΔG: B3LYP -29.5 -152.3 -154.9 -431.4 -236.6

ΔG: M06L -55.9 -226.0 -182.7 -653.2 -380.3

aThe units are kJ/mol.


at 3000.00 K.a

Species CuZn Cu2Zn CuSn Cu3Sn Cu3Zn

ΔH: B3LYP -61.3 -230.3 -190.2 -512.2 -315.6

ΔH: M06L -88.2 -307.1 -218.3 -770.0 -461.4

ΔS: B3LYP -0.078 -0.233 -0.089 -0.270 -0.264

ΔS: M06L -0.079 -0.243 -0.090 -0.334 -0.271

ΔG: B3LYP 172.0 468.4 79.7 299.2 476.8

ΔG: M06L 151.5 422.3 53.9 233.2 351.8

aThe units are kJ/mol.

Table 4-9 shows that the trend for the enthalpy and the entropy values at 3000.0 K were

similar to that at 298.15 K and the values were quite close. However, the Gibbs free energy

114

values in Table 4-9 are completely different with respect to the values at 298.15 K. This was

probably because the entropy values are negative for all species and at high temperatures the

TΔS factor is much higher than the ΔH factor for these alloys. Therefore, at high temperatures

the metal atoms would prefer to be in their atomic state in the gas phase rather than forming a

metal cluster.

Conclusion

Results for different metal sulfides and selenides obtained using both DFT functionals

B3LYP and M06L combined with basis set LANL2DZ were compared to the SGTE database.

DFT results for all metal sulfides and metal selenides using B3LYP /LANL2DZ provided results

closer to the SGTE database compared to the results from M06L/LANL2DZ except for Cu2S.

For species containing Zn, B3LYP/ LANL2DZ was found to give results comparable to the

SGTE database. Thermochemical values for SnSe2 in gas phase is not available in the SGTE

database. Results obtained for SnSe2 can be used to fill the database. Similarly, DFT results for

the metal clusters can also be used to fill the database. Results for metal clusters indicate that

their existence in gas phase at 3000.0 K is energetically not favorable.

Experimental Section

The thermochemical data for the possible gaseous binary species that take part in

equilibrium with the condensed phases of the CZTSSe are assessed by DFT using the Gaussian

09 package.118 For the sulfur allotropes DFT functional B3LYP combined with basis set 6-31G*

used for calculations. For all metal sulfides, metal selenides and metal clusters DFT functionals

B3LYP and M06L combined with basis set LANL2DZ have been used for calculations. The

thermochemical data (ΔG, ΔH and ΔS) were obtained within the rigid-rotator harmonic-

oscillation approximation. The optimized structures were visualized using Chemcraft.119 The

115

Cartesian coordinates for optimized structures are listed in Appendix C (from Table C-13 to

Table C-19).

116

APPENDIX A

NMR SPECTRA OF 35 AND 37

Figure A-1. 1H NMR of 35 (benzene-d6).

Figure A-2. gHMBC spectrum of 35 (benzene-d6).

117

Figure A-3. Variable temperature 1H NMR spectra for 35 (toluene-d8).

Figure A-4. Variable temperature 1H NMR spectra for 37 (toluene-d8).

118

APPENDIX B

CRYSTALLOGRAPHIC DATA

Crystallographic Data for 35

Table B-1. Crystal data and structure refinement for 35

Identification code 33

Empirical formula C14H34N4W

Formula weight 442.30

Temperature 100(2) K

Wavelength 0.71073 Å

Crystal system Orthorhombic

Space group P2(1)2(1)2(1)

Unit cell dimensions a = 15.2965(8) Å α = 90°.

b = 17.931(1) Å β = 90°.

c = 20.8790(11) Å γ = 90°.

Volume 5726.7(5) Å3

Z 12

Density (calculated) 1.539 Mg/m3

Absorption coefficient 6.048 mm-1

F(000) 2640

Crystal size 0.38 x 0.16 x 0.08 mm3

Theta range for data collection 1.50 to 27.50°.

Index ranges -18 ≤ h ≤ 19, -23 ≤ k ≤23, -27 ≤ l ≤ 27

Reflections collected 92465

Independent reflections 13145 [Rint = 0.0524]

Completeness to theta = 27.50° 100.0 %

Absorption correction Integration

Max. and min. transmission 0.6306 and 0.2095

Refinement method Full-matrix least-squares on F2

Data / restraints / parameters 13145 / 0 / 545

Goodness-of-fit on F2 0.980

Final R indices [I>2sigma(I)] R1 = 0.0214, wR2 = 0.0377 [11193]

R indices (all data) R1 = 0.0306, wR2 = 0.0393

Absolute structure parameter 0.497(6)

Largest diff. peak and hole 1.361 and -1.079 e.Å-3

R1 = (||Fo| - |Fc||) / |Fo|

119

wR2 = [w(Fo2 - Fc

2)2] / wFo22]]1/2

S = [w(Fo2 - Fc

2)2] / (n-p)]1/2

w= 1/[2(Fo2)+(m*p)2+n*p], p = [max(Fo

2,0)+ 2* Fc2]/3, m & n are constants

120

Table B-2. Atomic coordinates (x 104) and equivalent isotropic displacement parameters (Å2 x

103) for 35. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

W1A 20(1) 3228(1) 85(1) 17(1)

N1A -112(2) 3225(2) -718(1) 22(1)

N2A 1148(2) 3703(2) 235(2) 17(1)

N3A -2(2) 2177(1) 325(1) 24(1)

N4A -973(2) 3796(2) 424(2) 19(1)

C1A 1784(3) 4017(2) -235(2) 25(1)

C2A 2119(3) 3430(2) -694(2) 34(1)

C3A 1357(3) 4678(2) -595(2) 26(1)

C4A 1438(3) 3755(3) 910(2) 22(1)

C5A 1566(3) 4553(3) 1125(2) 38(1)

C6A 2236(3) 3267(3) 1042(2) 43(1)

C7A 65(3) 1945(2) 996(2) 32(1)

C8A -98(3) 1529(2) -94(2) 41(1)

C9A -1678(3) 4182(2) 68(2) 25(1)

C10A -1307(3) 4778(3) -363(2) 29(1)

C11A -2244(3) 3631(3) -298(2) 38(1)

C12A -1028(3) 3855(2) 1130(2) 19(1)

C13A -939(3) 4662(2) 1364(2) 28(1)

C14A -1833(2) 3482(2) 1402(2) 31(1)

W1B -140(1) 3415(1) 3406(1) 15(1)

N1B -96(2) 3516(2) 2608(1) 20(1)

N2B 966(2) 3800(2) 3735(2) 16(1)

N3B -1113(2) 4047(2) 3673(2) 22(1)

N4B -342(2) 2358(2) 3564(1) 17(1)

C1B 1036(3) 3849(2) 4436(2) 19(1)

C2B 1825(3) 3436(3) 4701(2) 32(1)

C3B 977(3) 4649(2) 4680(2) 30(1)

C4B 1685(3) 4154(2) 3375(2) 23(1)

C5B 2097(3) 3606(2) 2909(2) 30(1)

C6B 1393(3) 4869(2) 3035(2) 33(1)

C7B -1384(3) 4079(3) 4344(2) 31(1)

121

Table B-2. Continued

x y z U(eq)

C8B -1662(3) 4528(3) 3282(2) 34(1)

C9B -479(3) 1739(2) 3100(2) 25(1)

C10B -1233(3) 1900(2) 2650(2) 34(1)

C11B 365(3) 1584(2) 2724(2) 34(1)

C12B -398(2) 2138(2) 4241(2) 20(1)

C13B 302(3) 1585(2) 4436(2) 33(1)

C14B -1308(3) 1871(2) 4426(2) 33(1)

W1C 5081(1) 1614(1) 3249(1) 15(1)

N1C 5198(2) 1645(2) 4049(1) 22(1)

N2C 3932(2) 1162(2) 3108(2) 18(1)

N3C 6024(2) 964(2) 2953(2) 21(1)

N4C 5209(2) 2635(2) 2948(1) 16(1)

C1C 3331(3) 837(3) 3587(2) 26(1)

C2C 3779(3) 224(2) 3966(2) 34(1)

C3C 2946(3) 1440(3) 4010(2) 36(1)

C4C 3699(3) 1033(2) 2434(2) 23(1)

C5C 2817(3) 1367(3) 2254(2) 35(1)

C6C 3762(3) 206(2) 2265(2) 31(1)

C7C 6682(3) 583(3) 3336(2) 27(1)

C8C 6150(3) 817(3) 2277(2) 28(1)

C9C 5168(3) 2751(2) 2250(2) 20(1)

C10C 4409(3) 3252(2) 2056(2) 34(1)

C11C 6036(3) 3010(2) 1964(2) 28(1)

C12C 5380(3) 3318(2) 3325(2) 26(1)

C13C 6218(3) 3251(2) 3717(2) 37(1)

C14C 4588(3) 3502(2) 3752(2) 33(1)

122

Table B-3. Bond lengths (Å) and angles (°) for 35

Bond Bond Length (Å) / Bond Angle (°)

W1A-N1A 1.688(3)

W1A-N2A 1.949(3)

W1A-N3A 1.950(3)

W1A-N4A 1.961(4)

N2A-C4A 1.481(5)

N2A-C1A 1.491(5)

N3A-C8A 1.463(4)

N3A-C7A 1.464(4)

N4A-C12A 1.481(5)

N4A-C9A 1.481(5)

C1A-C2A 1.513(5)

C1A-C3A 1.548(6)

C1A-H1AA 1.0000

C2A-H2AA 0.9800‡‡‡‡‡‡

C2A-H2AB 0.9800

C2A-H2AC 0.9800

C3A-H3AA 0.9800

C3A-H3AB 0.9800

C3A-H3AC 0.9800

C4A-C6A 1.528(6)

‡‡‡‡‡‡ The hydrogens were placed arbitrarily so all C-H bond lengths were assumed to be 0.98 Å.

123



C4A-H4AA 1.0000

C5A-H5AA 0.9800

C5A-H5AB 0.9800

C5A-H5AC 0.9800

C6A-H6AA 0.9800

C6A-H6AB 0.9800

C6A-H6AC 0.9800

C7A-H7AA 0.9800

C7A-H7AB 0.9800

C7A-H7AC 0.9800

C8A-H8AA 0.9800

C8A-H8AB 0.9800

C8A-H8AC 0.9800

C9A-C10A 1.507(6)

C9A-C11A 1.520(6)

C9A-H9AA 1.0000

C10A-H10G 0.9800

C10A-H10H 0.9800

C10A-H10I 0.9800

C11A-H11G 0.9800

C11A-H11H 0.9800

124



C11A-H11I 0.9800

C12A-C14A 1.512(5)

C12A-C13A 1.534(5)

C12A-H12C 1.0000

C13A-H13G 0.9800

C13A-H13H 0.9800

C13A-H13I 0.9800

C14A-H14G 0.9800

C14A-H14H 0.9800

C14A-H14I 0.9800

W1B-N1B 1.679(3)

W1B-N4B 1.948(3)

W1B-N3B 1.951(4)

W1B-N2B 1.952(4)

N2B-C1B 1.472(5)

N2B-C4B 1.475(5)

N3B-C8B 1.455(5)

N3B-C7B 1.463(6)

N4B-C12B 1.471(4)

N4B-C9B 1.489(5)

C1B-C2B 1.520(5)

125



C1B-C3B 1.525(5)

C1B-H1BA 1.0000

C2B-H2BA 0.9800

C2B-H2BB 0.9800

C2B-H2BC 0.9800

C3B-H3BA 0.9800

C3B-H3BB 0.9800

C3B-H3BC 0.9800

C4B-C5B 1.520(6)

C4B-C6B 1.531(6)

C4B-H4BA 1.0000

C5B-H5BA 0.9800

C5B-H5BB 0.9800

C5B-H5BC 0.9800

C6B-H6BA 0.9800

C6B-H6BB 0.9800

C6B-H6BC 0.9800

C7B-H7BA 0.9800

C7B-H7BB 0.9800

C7B-H7BC 0.9800

C8B-H8BA 0.9800

126



C8B-H8BB 0.9800

C8B-H8BC 0.9800

C9B-C10B 1.515(5)

C9B-C11B 1.536(5)

C9B-H9BA 1.0000

C10B-H10A 0.9800

C10B-H10B 0.9800

C10B-H10C 0.9800

C11B-H11A 0.9800

C11B-H11B 0.9800

C11B-H11C 0.9800

C12B-C13B 1.515(5)

C12B-C14B 1.522(5)

C12B-H12A 1.0000

C13B-H13A 0.9800

C13B-H13B 0.9800

C13B-H13C 0.9800

C14B-H14A 0.9800

C14B-H14B 0.9800

C14B-H14C 0.9800

W1C-N1C 1.681(3)

127



W1C-N4C 1.945(3)

W1C-N3C 1.955(3)

W1C-N2C 1.957(4)

N2C-C4C 1.470(5)

N2C-C1C 1.479(5)

N3C-C8C 1.449(5)

N3C-C7C 1.456(5)

N4C-C9C 1.474(4)

N4C-C12C 1.479(4)

C1C-C3C 1.515(6)

C1C-C2C 1.519(6)

C1C-H1CA 1.0000

C2C-H2CA 0.9800

C2C-H2CB 0.9800

C2C-H2CC 0.9800

C3C-H3CA 0.9800

C3C-H3CB 0.9800

C3C-H3CC 0.9800

C4C-C5C 1.524(6)

C4C-C6C 1.527(5)

C4C-H4CA 1.0000

128



C5C-H5CA 0.9800

C5C-H5CB 0.9800

C5C-H5CC 0.9800

C6C-H6CA 0.9800

C6C-H6CB 0.9800

C6C-H6CC 0.9800

C7C-H7CA 0.9800

C7C-H7CB 0.9800

C7C-H7CC 0.9800

C8C-H8CA 0.9800

C8C-H8CB 0.9800

C8C-H8CC 0.9800

C9C-C10C 1.523(5)

C9C-C11C 1.529(5)

C9C-H9CA 1.0000

C10C-H10D 0.9800

C10C-H10E 0.9800

C10C-H10F 0.9800

C11C-H11D 0.9800

C11C-H11E 0.9800

C11C-H11F 0.9800

129



C12C-C13C 1.527(5)

C12C-C14C 1.540(5)

C12C-H12B 1.0000

C13C-H13D 0.9800

C13C-H13E 0.9800

C13C-H13F 0.9800

C14C-H14D 0.9800

C14C-H14E 0.9800

C14C-H14F 0.9800

N1A-W1A-N2A 105.47(15)

N1A-W1A-N3A 104.52(12)

N2A-W1A-N3A 113.33(15)

N1A-W1A-N4A 105.45(16)

N2A-W1A-N4A 113.65(14)

N3A-W1A-N4A 113.29(15)

C4A-N2A-C1A 114.0(3)

C4A-N2A-W1A 116.4(3)

C1A-N2A-W1A 129.5(3)

C8A-N3A-C7A 110.7(3)

C8A-N3A-W1A 128.0(2)

130



C7A-N3A-W1A 121.3(2)

C12A-N4A-C9A 115.2(4)

C12A-N4A-W1A 116.1(3)

C9A-N4A-W1A 128.8(3)

N2A-C1A-C2A 112.0(4)

N2A-C1A-C3A 109.5(3)

C2A-C1A-C3A 111.5(4)

N2A-C1A-H1AA 107.9

C2A-C1A-H1AA 107.9

C3A-C1A-H1AA 107.9

C1A-C2A-H2AA 109.5§§§§§§

C1A-C2A-H2AB 109.5

H2AA-C2A-H2AB 109.5

C1A-C2A-H2AC 109.5

H2AA-C2A-H2AC 109.5

H2AB-C2A-H2AC 109.5

C1A-C3A-H3AA 109.5

C1A-C3A-H3AB 109.5

H3AA-C3A-H3AB 109.5

C1A-C3A-H3AC 109.5

§§§§§§ The hydrogens were placed arbitrarily so all bond angles consisting of hydrogen were assumed to be 109.5°.

131



H3AA-C3A-H3AC 109.5

H3AB-C3A-H3AC 109.5

N2A-C4A-C5A 112.4(4)

N2A-C4A-C6A 112.0(3)

C5A-C4A-C6A 112.6(4)

N2A-C4A-H4AA 106.4

C5A-C4A-H4AA 106.4

C6A-C4A-H4AA 106.4

C4A-C5A-H5AA 109.5

C4A-C5A-H5AB 109.5

H5AA-C5A-H5AB 109.5

C4A-C5A-H5AC 109.5

H5AA-C5A-H5AC 109.5

H5AB-C5A-H5AC 109.5

C4A-C6A-H6AA 109.5

C4A-C6A-H6AB 109.5

H6AA-C6A-H6AB 109.5

C4A-C6A-H6AC 109.5

H6AA-C6A-H6AC 109.5

H6AB-C6A-H6AC 109.5

N3A-C7A-H7AA 109.5

132



N3A-C7A-H7AB 109.5

H7AA-C7A-H7AB 109.5

N3A-C7A-H7AC 109.5

H7AA-C7A-H7AC 109.5

H7AB-C7A-H7AC 109.5

N3A-C8A-H8AA 109.5

N3A-C8A-H8AB 109.5

H8AA-C8A-H8AB 109.5

N3A-C8A-H8AC 109.5

H8AA-C8A-H8AC 109.5

H8AB-C8A-H8AC 109.5

N4A-C9A-C10A 110.8(4)

N4A-C9A-C11A 111.3(4)

C10A-C9A-C11A 112.1(4)

N4A-C9A-H9AA 107.5

C10A-C9A-H9AA 107.5

C11A-C9A-H9AA 107.5

C9A-C10A-H10G 109.5

C9A-C10A-H10H 109.5

H10G-C10A-H10H 109.5

C9A-C10A-H10I 109.5

133



H10G-C10A-H10I 109.5

H10H-C10A-H10I 109.5

C9A-C11A-H11G 109.5

C9A-C11A-H11H 109.5

H11G-C11A-H11H 109.5

C9A-C11A-H11I 109.5

H11G-C11A-H11I 109.5

H11H-C11A-H11I 109.5

N4A-C12A-C14A 112.9(3)

N4A-C12A-C13A 112.3(3)

C14A-C12A-C13A 111.7(4)

N4A-C12A-H12C 106.5

C14A-C12A-H12C 106.5

C13A-C12A-H12C 106.5

C12A-C13A-H13G 109.5

C12A-C13A-H13H 109.5

H13G-C13A-H13H 109.5

C12A-C13A-H13I 109.5

H13G-C13A-H13I 109.5

H13H-C13A-H13I 109.5

C12A-C14A-H14G 109.5

134



C12A-C14A-H14H 109.5

H14G-C14A-H14H 109.5

C12A-C14A-H14I 109.5

H14G-C14A-H14I 109.5

H14H-C14A-H14I 109.5

N1B-W1B-N4B 106.20(13)

N1B-W1B-N3B 104.50(16)

N4B-W1B-N3B 113.27(14)

N1B-W1B-N2B 106.04(15)

N4B-W1B-N2B 115.00(14)

N3B-W1B-N2B 110.87(14)

C1B-N2B-C4B 115.3(4)

C1B-N2B-W1B 115.7(3)

C4B-N2B-W1B 128.2(3)

C8B-N3B-C7B 110.5(4)

C8B-N3B-W1B 128.7(3)

C7B-N3B-W1B 120.8(3)

C12B-N4B-C9B 114.7(3)

C12B-N4B-W1B 115.6(2)

C9B-N4B-W1B 129.6(2)

N2B-C1B-C2B 113.0(3)

135



N2B-C1B-C3B 112.6(4)

C2B-C1B-C3B 112.6(4)

N2B-C1B-H1BA 106.0

C2B-C1B-H1BA 106.0

C3B-C1B-H1BA 106.0

C1B-C2B-H2BA 109.5

C1B-C2B-H2BB 109.5

H2BA-C2B-H2BB 109.5

C1B-C2B-H2BC 109.5

H2BA-C2B-H2BC 109.5

H2BB-C2B-H2BC 109.5

C1B-C3B-H3BA 109.5

C1B-C3B-H3BB 109.5

H3BA-C3B-H3BB 109.5

C1B-C3B-H3BC 109.5

H3BA-C3B-H3BC 109.5

H3BB-C3B-H3BC 109.5

N2B-C4B-C5B 111.0(4)

N2B-C4B-C6B 112.3(3)

C5B-C4B-C6B 111.4(4)

N2B-C4B-H4BA 107.3

136



C5B-C4B-H4BA 107.3

C6B-C4B-H4BA 107.3

C4B-C5B-H5BA 109.5

C4B-C5B-H5BB 109.5

H5BA-C5B-H5BB 109.5

C4B-C5B-H5BC 109.5

H5BA-C5B-H5BC 109.5

H5BB-C5B-H5BC 109.5

C4B-C6B-H6BA 109.5

C4B-C6B-H6BB 109.5

H6BA-C6B-H6BB 109.5

C4B-C6B-H6BC 109.5

H6BA-C6B-H6BC 109.5

H6BB-C6B-H6BC 109.5

N3B-C7B-H7BA 109.5

N3B-C7B-H7BB 109.5

H7BA-C7B-H7BB 109.5

N3B-C7B-H7BC 109.5

H7BA-C7B-H7BC 109.5

H7BB-C7B-H7BC 109.5

N3B-C8B-H8BA 109.5

137



N3B-C8B-H8BB 109.5

H8BA-C8B-H8BB 109.5

N3B-C8B-H8BC 109.5

H8BA-C8B-H8BC 109.5

H8BB-C8B-H8BC 109.5

N4B-C9B-C10B 111.6(3)

N4B-C9B-C11B 110.4(3)

C10B-C9B-C11B 111.0(3)

N4B-C9B-H9BA 107.9

C10B-C9B-H9BA 107.9

C11B-C9B-H9BA 107.9

C9B-C10B-H10A 109.5

C9B-C10B-H10B 109.5

H10A-C10B-H10B 109.5

C9B-C10B-H10C 109.5

H10A-C10B-H10C 109.5

H10B-C10B-H10C 109.5

C9B-C11B-H11A 109.5

C9B-C11B-H11B 109.5

H11A-C11B-H11B 109.5

C9B-C11B-H11C 109.5

138



H11A-C11B-H11C 109.5

H11B-C11B-H11C 109.5

N4B-C12B-C13B 113.1(3)

N4B-C12B-C14B 112.4(3)

C13B-C12B-C14B 111.8(3)

N4B-C12B-H12A 106.3

C13B-C12B-H12A 106.3

C14B-C12B-H12A 106.3

C12B-C13B-H13A 109.5

C12B-C13B-H13B 109.5

H13A-C13B-H13B 109.5

C12B-C13B-H13C 109.5

H13A-C13B-H13C 109.5

H13B-C13B-H13C 109.5

C12B-C14B-H14A 109.5

C12B-C14B-H14B 109.5

H14A-C14B-H14B 109.5

C12B-C14B-H14C 109.5

H14A-C14B-H14C 109.5

H14B-C14B-H14C 109.5

N1C-W1C-N4C 106.17(12)

139



N1C-W1C-N3C 104.84(16)

N4C-W1C-N3C 112.64(15)

N1C-W1C-N2C 104.95(16)

N4C-W1C-N2C 115.55(14)

N3C-W1C-N2C 111.62(15)

C4C-N2C-C1C 115.7(4)

C4C-N2C-W1C 115.3(3)

C1C-N2C-W1C 128.3(3)

C8C-N3C-C7C 111.1(3)

C8C-N3C-W1C 121.0(3)

C7C-N3C-W1C 128.0(3)

C9C-N4C-C12C 114.7(3)

C9C-N4C-W1C 116.6(2)

C12C-N4C-W1C 128.7(2)

N2C-C1C-C3C 110.8(4)

N2C-C1C-C2C 110.9(4)

C3C-C1C-C2C 112.8(4)

N2C-C1C-H1CA 107.3

C3C-C1C-H1CA 107.3

C2C-C1C-H1CA 107.3

C1C-C2C-H2CA 109.5

140



C1C-C2C-H2CB 109.5

H2CA-C2C-H2CB 109.5

C1C-C2C-H2CC 109.5

H2CA-C2C-H2CC 109.5

H2CB-C2C-H2CC 109.5

C1C-C3C-H3CA 109.5

C1C-C3C-H3CB 109.5

H3CA-C3C-H3CB 109.5

C1C-C3C-H3CC 109.5

H3CA-C3C-H3CC 109.5

H3CB-C3C-H3CC 109.5

N2C-C4C-C5C 113.0(3)

N2C-C4C-C6C 111.1(4)

C5C-C4C-C6C 112.4(4)

N2C-C4C-H4CA 106.7

C5C-C4C-H4CA 106.7

C6C-C4C-H4CA 106.7

C4C-C5C-H5CA 109.5

C4C-C5C-H5CB 109.5

H5CA-C5C-H5CB 109.5

C4C-C5C-H5CC 109.5

141



H5CA-C5C-H5CC 109.5

H5CB-C5C-H5CC 109.5

C4C-C6C-H6CA 109.5

C4C-C6C-H6CB 109.5

H6CA-C6C-H6CB 109.5

C4C-C6C-H6CC 109.5

H6CA-C6C-H6CC 109.5

H6CB-C6C-H6CC 109.5

N3C-C7C-H7CA 109.5

N3C-C7C-H7CB 109.5

H7CA-C7C-H7CB 109.5

N3C-C7C-H7CC 109.5

H7CA-C7C-H7CC 109.5

H7CB-C7C-H7CC 109.5

N3C-C8C-H8CA 109.5

N3C-C8C-H8CB 109.5

H8CA-C8C-H8CB 109.5

N3C-C8C-H8CC 109.5

H8CA-C8C-H8CC 109.5

H8CB-C8C-H8CC 109.5

N4C-C9C-C10C 112.2(3)

142



N4C-C9C-C11C 113.1(3)

C10C-C9C-C11C 112.2(3)

N4C-C9C-H9CA 106.2

C10C-C9C-H9CA 106.2

C11C-C9C-H9CA 106.2

C9C-C10C-H10D 109.5

C9C-C10C-H10E 109.5

H10D-C10C-H10E 109.5

C9C-C10C-H10F 109.5

H10D-C10C-H10F 109.5

H10E-C10C-H10F 109.5

C9C-C11C-H11D 109.5

C9C-C11C-H11E 109.5

H11D-C11C-H11E 109.5

C9C-C11C-H11F 109.5

H11D-C11C-H11F 109.5

H11E-C11C-H11F 109.5

N4C-C12C-C13C 111.7(3)

N4C-C12C-C14C 110.3(3)

C13C-C12C-C14C 111.5(3)

N4C-C12C-H12B 107.7

143



C13C-C12C-H12B 107.7

C14C-C12C-H12B 107.7

C12C-C13C-H13D 109.5

C12C-C13C-H13E 109.5

H13D-C13C-H13E 109.5

C12C-C13C-H13F 109.5

H13D-C13C-H13F 109.5

H13E-C13C-H13F 109.5

C12C-C14C-H14D 109.5

C12C-C14C-H14E 109.5

H14D-C14C-H14E 109.5

C12C-C14C-H14F 109.5

H14D-C14C-H14F 109.5

H14E-C14C-H14F 109.5

Symmetry transformations used to generate equivalent atoms

144

Table B-4. Anisotropic displacement parameters (Å2 x 103) for 35. The anisotropic displacement

factor exponent takes the form: -2π2[ h2 a*2U11 + ... + 2 h k a* b* U12.

U11 U22 U33 U23 U13 U12

W1A 21(1) 16(1) 14(1) 1(1) -1(1) -2(1)

N1A 22(2) 21(2) 25(2) -1(1) -2(2) -5(2)

N2A 15(2) 21(2) 16(2) 1(2) 0(2) 0(2)

N3A 37(2) 16(2) 20(2) 2(1) 4(2) -1(2)

N4A 16(2) 27(2) 14(2) 3(2) 0(2) 1(2)

C1A 18(3) 29(3) 26(3) -2(2) -1(2) -5(2)

C2A 35(3) 43(3) 24(3) 7(2) 6(2) 10(3)

C3A 25(3) 23(3) 31(3) 8(2) 5(2) -9(2)

C4A 15(2) 34(3) 18(3) -2(2) 0(2) -2(2)

C5A 32(3) 49(3) 35(3) -10(2) -5(2) -7(3)

C6A 35(3) 73(4) 21(3) 2(2) -2(2) 18(3)

C7A 41(3) 25(2) 30(2) 6(2) 5(2) 1(3)

C8A 67(4) 22(2) 35(3) 0(2) -3(2) -12(3)

C9A 21(3) 25(2) 29(3) 5(2) 2(2) 2(2)

C10A 28(3) 31(3) 26(3) 8(2) -5(2) 7(2)

C11A 33(3) 45(3) 37(3) 11(2) -13(2) -8(2)

C12A 16(2) 21(2) 19(3) 1(2) 0(2) 4(2)

C13A 33(3) 26(3) 26(3) 2(2) 8(2) 5(2)

C14A 26(2) 36(3) 30(3) 4(2) 0(2) -7(2)

W1B 14(1) 16(1) 14(1) 1(1) -1(1) 0(1)

N1B 18(2) 21(2) 22(2) 2(1) -4(2) -1(2)

N2B 13(2) 17(2) 19(2) 0(2) 1(2) -2(2)

N3B 18(2) 23(2) 24(2) 2(2) 1(2) 8(2)

N4B 17(2) 18(2) 15(2) 2(1) 1(1) -1(1)

C1B 20(3) 21(2) 15(2) -2(2) -4(2) 1(2)

C2B 23(2) 43(3) 29(3) 4(2) -4(2) 1(2)

C3B 36(3) 32(3) 23(3) -3(2) 1(2) -5(2)

C4B 16(2) 29(3) 23(3) 1(2) -1(2) -5(2)

C5B 18(2) 41(3) 31(3) 1(2) 6(2) -1(2)

C6B 35(3) 26(3) 37(3) 5(2) 6(2) -9(2)

C7B 24(3) 41(3) 27(3) 1(2) 2(2) 14(2)

C8B 30(3) 42(3) 32(3) 9(2) -1(2) 14(2)

145


U11 U22 U33 U23 U13 U12

C9B 34(3) 20(3) 22(2) 3(2) 1(2) -4(2)

C10B 42(3) 31(3) 30(3) -8(2) -8(2) -10(2)

C11B 45(3) 31(3) 27(3) -3(2) 5(2) 8(2)

C12B 18(2) 18(2) 24(2) -1(2) 2(2) -1(2)

C13B 40(3) 30(2) 30(2) 1(2) 2(2) 2(2)

C14B 34(3) 35(3) 30(3) 4(2) 8(2) -8(2)

W1C 14(1) 17(1) 14(1) 0(1) 0(1) -1(1)

N1C 22(2) 22(2) 22(2) -1(1) -1(2) 0(2)

N2C 19(2) 20(2) 14(2) -4(2) 0(2) -1(2)

N3C 19(2) 22(2) 21(2) 0(2) 1(2) 8(2)

N4C 20(2) 17(2) 13(2) -4(1) -3(1) -1(2)

C1C 17(2) 34(3) 25(3) 1(2) -1(2) -10(2)

C2C 38(3) 30(3) 35(3) -1(2) 3(2) -14(2)

C3C 21(3) 59(4) 27(3) 1(2) 7(2) 4(3)

C4C 20(3) 26(3) 22(3) -1(2) 0(2) -7(2)

C5C 24(3) 45(3) 36(3) 1(2) -7(2) -3(2)

C6C 27(3) 38(3) 30(3) -10(2) -4(2) -9(2)

C7C 23(3) 30(3) 29(3) 3(2) 1(2) 8(2)

C8C 27(3) 34(3) 22(3) -4(2) 2(2) 14(2)

C9C 20(2) 23(2) 16(2) 2(1) 4(2) 1(2)

C10C 31(3) 47(3) 25(3) 10(2) 0(2) 10(2)

C11C 31(3) 28(3) 24(2) 2(2) 5(2) -5(2)

C12C 37(2) 17(2) 25(3) 2(2) -1(2) 1(2)

C13C 40(3) 32(3) 38(3) -12(2) -5(2) -12(2)

C14C 44(3) 25(2) 28(2) -5(2) 0(2) 11(2)

146

Table B-5. Hydrogen coordinates (x 104) and isotropic displacement parameters (Å2 x 10 3) for

35.

x y z U(eq)

H1AA 2295 4215 11 29

H2AA 2409 3032 -453 51

H2AB 2537 3658 -991 51

H2AC 1628 3221 -936 51

H3AA 1210 5073 -289 39

H3AB 824 4507 -810 39

H3AC 1768 4873 -914 39

H4AA 951 3548 1176 27

H5AA 1050 4848 1010 58

H5AB 2083 4762 913 58

H5AC 1649 4566 1590 58

H6AA 2098 2747 939 64

H6AB 2397 3306 1496 64

H6AC 2726 3435 777 64

H7AA -455 1656 1113 48

H7AB 106 2387 1270 48

H7AC 588 1636 1052 48

H8AA 383 1180 -17 62

H8AB -86 1691 -542 62

H8AC -656 1281 -5 62

H9AA -2060 4435 390 30

H10G -939 5116 -110 43

H10H -1785 5060 -559 43

H10I -953 4544 -699 43

H11G -2498 3270 2 58

H11H -1886 3367 -614 58

H11I -2714 3900 -518 58

H12C -514 3577 1305 22

H13G -448 4902 1144 42

H13H -833 4665 1827 42

H13I -1479 4935 1270 42

H14G -1860 2964 1253 46

147


x y z U(eq)

H14H -2356 3750 1258 46

H14I -1806 3491 1871 46

H1BA 511 3585 4610 23

H2BA 1837 2928 4528 48

H2BB 1787 3415 5169 48

H2BC 2361 3699 4576 48

H3BA 462 4892 4495 45

H3BB 1504 4923 4555 45

H3BC 926 4646 5148 45

H4BA 2145 4297 3692 27

H5BA 2303 3167 3143 45

H5BB 2592 3845 2692 45

H5BC 1662 3454 2590 45

H6BA 1162 5221 3351 49

H6BB 937 4749 2722 49

H6BC 1894 5093 2815 49

H7BA -1352 4595 4496 46

H7BB -995 3766 4603 46

H7BC -1986 3898 4383 46

H8BA -2276 4389 3339 52

H8BB -1500 4471 2830 52

H8BC -1578 5048 3412 52

H9BA -627 1280 3349 30

H10A -1769 1972 2899 51

H10B -1310 1479 2356 51

H10C -1107 2353 2404 51

H11A 838 1466 3024 51

H11B 523 2027 2474 51

H11C 273 1162 2434 51

H12A -288 2601 4497 24

H13A 875 1770 4300 50

H13B 186 1103 4233 50

148


x y z U(eq)

H13C 296 1525 4903 50

H14A -1742 2242 4292 50

H14B -1339 1804 4891 50

H14C -1429 1395 4214 50

H1CA 2836 603 3347 31

H2CA 4023 -146 3671 51

H2CB 3353 -18 4249 51

H2CC 4251 439 4224 51

H3CA 2630 1801 3745 54

H3CB 3418 1695 4241 54

H3CC 2542 1214 4319 54

H4CA 4148 1296 2170 27

H5CA 2807 1897 2370 52

H5CB 2351 1104 2484 52

H5CC 2725 1315 1791 52

H6CA 4344 19 2378 47

H6CB 3665 141 1804 47

H6CC 3317 -72 2503 47

H7CA 6629 43 3273 41

H7CB 6593 702 3790 41

H7CC 7266 747 3204 41

H8CA 6737 975 2149 42

H8CB 5714 1094 2028 42

H8CC 6082 282 2195 42

H9CA 5045 2251 2057 24

H10D 3873 3081 2267 52

H10E 4332 3231 1590 52

H10F 4534 3767 2185 52

H11D 6504 2671 2098 42

H11E 6167 3516 2115 42

H11F 5994 3011 1495 42

H12B 5458 3739 3017 32

149


x y z U(eq)

H13D 6710 3143 3431 55

H13E 6156 2847 4030 55

H13F 6327 3721 3943 55

H14D 4064 3551 3485 49

H14E 4695 3973 3978 49

H14F 4502 3101 4065 49

150

APPENDIX C

COMPUTATIONAL DATA

Cartesian Coordinates for the Decomposition Pathway of 35

Table C-1. Optimized Cartesian coordinates of the GS in the decomposition pathway of 35.

x y z

W 0.035447000 0.548742000 -0.418762000

N -1.668846000 -0.422585000 -0.130429000

N 0.069720000 2.358788000 0.387924000

N 1.625086000 -0.553853000 -0.002960000

N 0.132578000 0.801648000 -2.074659000

C 0.137819000 3.631916000 -0.297015000

H 0.092738000 3.477978000 -1.377227000

C 0.133622000 2.523822000 1.824828000

H 0.057651000 1.556819000 2.343259000

C 1.671079000 -1.027376000 1.391558000

C 2.954319000 -0.696546000 2.144397000

H 0.875937000 -0.452095000 1.906632000

H 2.839320000 -0.941734000 3.207727000

H 3.808287000 -1.273148000 1.770184000

H 3.199070000 0.368740000 2.061101000

C 2.716487000 -0.841703000 -0.954948000

C 3.871374000 0.152942000 -0.845079000

H 2.256857000 -0.675377000 -1.936973000

H 4.553259000 0.035576000 -1.697209000

151

Table C-1. Continued

x y z

H 3.491270000 1.181658000 -0.856304000

H 4.462113000 0.016281000 0.067812000

C -2.463668000 -1.041335000 -1.210060000

C -2.202950000 -2.541763000 -1.343025000

H -2.068241000 -0.578291000 -2.122844000

H -2.629822000 -2.917531000 -2.281775000

H -1.124083000 -2.742274000 -1.360417000

H -2.645855000 -3.124237000 -0.527208000

C -2.112780000 -0.461811000 1.275854000

C -2.578632000 -1.822384000 1.783095000

H -1.204122000 -0.223611000 1.864839000

H -2.750756000 -1.774758000 2.865565000

H -3.522471000 -2.131072000 1.319702000

H -1.834059000 -2.602332000 1.591699000

C 3.217112000 -2.280266000 -0.936276000

H 3.911693000 -2.436213000 -1.770745000

H 3.763102000 -2.526660000 -0.016669000

H 2.392181000 -2.993318000 -1.047308000

C 1.269218000 -2.493958000 1.557993000

H 2.077784000 -3.184219000 1.296309000

H 0.991768000 -2.696607000 2.601019000

152


x y z

H 0.404947000 -2.723567000 0.922534000

C -3.116399000 0.640582000 1.618805000

H -4.113959000 0.431558000 1.218095000

H -3.213525000 0.745265000 2.707551000

H -2.779499000 1.600695000 1.209394000

C -3.955613000 -0.732888000 -1.172575000

H -4.138866000 0.346266000 -1.127190000

H -4.429560000 -1.115223000 -2.085012000

H -4.468409000 -1.204453000 -0.325057000

H 1.082259000 2.992667000 2.138684000

H -0.689139000 3.160152000 2.194063000

H 1.072062000 4.166928000 -0.053898000

H -0.698686000 4.285854000 0.003616000

Table C-2. Optimized Cartesian coordinates for TS in the decomposition pathway of 35.

x y z

N 1.778550000 -0.596691000 0.168895000

W -0.121492000 0.385928000 -0.274183000

N -0.281905000 2.282982000 0.254729000

N -0.204583000 0.454191000 -1.952594000

N -1.724263000 -0.585868000 0.355418000

H 0.632210000 -1.370012000 0.258187000

153


x y z

C -3.061655000 -0.598546000 -0.229745000

C -3.984594000 -1.481083000 0.600432000

H -3.012432000 -1.000983000 -1.259107000

H -5.003420000 -1.478875000 0.193520000

H -3.635694000 -2.520531000 0.621163000

H -4.024944000 -1.122085000 1.636776000

C -0.842212000 -1.748734000 0.270243000

C -0.777444000 -2.535445000 1.574217000

H 0.129963000 -3.153006000 1.644378000

H -0.816023000 -1.874309000 2.445194000

H -1.636892000 -3.219158000 1.645185000

C 2.722884000 -0.864442000 -0.933283000

C 2.131684000 -1.818624000 -1.955510000

H 3.581809000 -1.385211000 -0.484153000

H 2.886270000 -2.061440000 -2.712573000

H 1.819546000 -2.756609000 -1.480018000

H 1.267567000 -1.382592000 -2.468482000

C 2.362997000 -0.002498000 1.391606000

C 1.424347000 -0.221286000 2.571262000

H 2.477287000 1.091272000 1.243752000

H 1.730621000 0.387193000 3.429749000

154


x y z

H 0.379673000 0.038311000 2.348582000

H 1.429353000 -1.275335000 2.873952000

C -0.283840000 3.434210000 -0.626848000

H 0.493667000 4.157835000 -0.331443000

C -0.555828000 2.672892000 1.624949000

H -0.758221000 1.799268000 2.255000000

C 3.734998000 -0.559298000 1.753607000

H 3.705069000 -1.654372000 1.823347000

H 4.512217000 -0.280742000 1.034477000

H 4.039500000 -0.168529000 2.731657000

C 3.228850000 0.418838000 -1.580192000

H 4.000551000 0.206543000 -2.330508000

H 2.404669000 0.943566000 -2.080902000

H 3.666428000 1.098913000 -0.836978000

C -1.069224000 -2.674892000 -0.916883000

H -0.266290000 -3.419906000 -0.983185000

H -2.010799000 -3.236778000 -0.806096000

H -1.100482000 -2.135276000 -1.869360000

C -3.572878000 0.830308000 -0.305665000

H -3.576528000 1.289818000 0.692244000

H -2.936682000 1.441358000 -0.958440000

155


x y z

H -4.595071000 0.861271000 -0.700753000

H -0.102165000 3.119397000 -1.656839000

H -1.253397000 3.958697000 -0.578731000

H 0.286422000 3.231610000 2.066552000

H -1.446443000 3.321324000 1.669132000

Table C-3. Optimized Cartesian coordinates for INT1 in the decomposition pathway of 35.

x y z

N 1.925638000 -0.613137000 0.277322000

W -0.162564000 0.209948000 -0.306885000

N -0.229879000 2.189530000 0.002431000

N -0.243329000 -0.066069000 -1.970190000

N -1.890296000 -0.399207000 0.463827000

H 1.717215000 -1.438269000 0.845701000

C -3.190363000 -0.443706000 -0.192677000

C -4.206390000 -1.082583000 0.746076000

H -3.127900000 -1.051112000 -1.116214000

H -5.198648000 -1.137143000 0.280385000

H -3.907484000 -2.100621000 1.023821000

H -4.290897000 -0.495811000 1.670035000

C -1.041700000 -1.545835000 0.611611000

C -0.762344000 -1.931196000 2.051569000

156


x y z

H 0.184120000 -2.488947000 2.165393000

H -0.717880000 -1.049223000 2.702686000

H -1.550229000 -2.590153000 2.458234000

C 2.791360000 -1.097018000 -0.852350000

C 2.125966000 -2.274171000 -1.537691000

H 3.727573000 -1.454870000 -0.397433000

H 2.803700000 -2.691136000 -2.290873000

H 1.895968000 -3.074069000 -0.821163000

H 1.195737000 -1.970575000 -2.030276000

C 2.596221000 0.379534000 1.190785000

C 1.779730000 0.483067000 2.465732000

H 2.555744000 1.343022000 0.661623000

H 2.154680000 1.294685000 3.098281000

H 0.720792000 0.686174000 2.267601000

H 1.833124000 -0.448900000 3.044373000

C -0.094957000 3.200867000 -1.026812000

H 0.721491000 3.906154000 -0.790633000

C -0.599341000 2.783196000 1.268476000

H -0.926248000 2.012829000 1.978746000

C 4.043596000 0.043134000 1.518472000

H 4.131162000 -0.961691000 1.953033000

157


x y z

H 4.706752000 0.098481000 0.649527000

H 4.420696000 0.754161000 2.261712000

C 3.106787000 0.037749000 -1.806103000

H 3.769117000 -0.320532000 -2.601487000

H 2.186133000 0.410744000 -2.271107000

H 3.613160000 0.872959000 -1.305737000

C -1.310077000 -2.763723000 -0.253742000

H -0.446487000 -3.444013000 -0.246442000

H -2.167955000 -3.353718000 0.118354000

H -1.501080000 -2.501385000 -1.299383000

C -3.601632000 0.965291000 -0.585944000

H -3.631484000 1.615211000 0.299510000

H -2.888610000 1.396657000 -1.299762000

H -4.595755000 0.971601000 -1.049173000

H 0.113523000 2.735250000 -1.993754000

H -1.020217000 3.797019000 -1.115787000

H 0.233806000 3.349326000 1.722996000

H -1.439926000 3.486258000 1.138529000

158


x y z

W 1.862516000 -0.421261000 -0.129495000

N 0.943534000 -0.862149000 1.278865000

N 2.549131000 -1.983607000 -1.134281000

N 2.760301000 1.376098000 -0.148742000

N 0.174818000 0.300278000 -1.023450000

W -1.001910000 0.052641000 0.282194000

N -0.986477000 1.026973000 2.032203000

N -2.395612000 1.139579000 -0.652986000

N -1.851150000 -1.719589000 0.180757000

C -2.042446000 0.711343000 2.967712000

H -2.911757000 0.265145000 2.463847000

C 0.157288000 1.585903000 2.706268000

H 0.938688000 1.838497000 1.985753000

C -3.726845000 1.213063000 -0.018976000

C -4.914336000 1.166426000 -0.976543000

H -3.788813000 0.284507000 0.578919000

H -5.840580000 1.089739000 -0.392996000

H -4.990381000 2.078621000 -1.579018000

H -4.870967000 0.308939000 -1.654534000

C -2.077119000 2.031809000 -1.792260000

C -2.535872000 1.475783000 -3.137983000

159


x y z

H -0.983040000 2.026262000 -1.831346000

H -2.164255000 2.117803000 -3.947204000

H -2.120743000 0.473855000 -3.296866000

H -3.625113000 1.419628000 -3.239585000

C -1.948618000 -2.389710000 1.494135000

C -3.392334000 -2.733984000 1.835902000

H -1.585397000 -1.662701000 2.238980000

H -3.465001000 -3.171996000 2.838887000

H -4.029851000 -1.840621000 1.802471000

H -3.806441000 -3.463329000 1.127374000

C -2.167371000 -2.555275000 -0.989674000

C -3.382136000 -2.017934000 -1.729245000

H -2.431625000 -3.550877000 -0.601433000

H -3.644108000 -2.666145000 -2.574824000

H -4.250715000 -1.951306000 -1.062278000

H -3.180397000 -1.013614000 -2.119141000

C 3.237194000 -1.796399000 -2.394010000

H 3.244949000 -0.736828000 -2.679576000

H 2.732744000 -2.356999000 -3.199169000

C 2.548031000 -3.368369000 -0.722096000

H 2.013846000 -3.485522000 0.225785000

160


x y z

H 3.578259000 -3.741435000 -0.588540000

C 3.672692000 0.529241000 0.541132000

C 3.861895000 0.746375000 2.028690000

H 4.525673000 1.605805000 2.230137000

H 2.910039000 0.925081000 2.541677000

H 4.326583000 -0.130237000 2.498007000

C 2.567899000 2.777431000 0.175014000

C 3.760403000 3.577929000 -0.342238000

H 2.539916000 2.914084000 1.275309000

H 3.664911000 4.641980000 -0.089323000

H 4.697717000 3.209933000 0.092158000

H 3.838563000 3.485521000 -1.432829000

H 2.065341000 -4.009409000 -1.479856000

H 4.283107000 -2.144502000 -2.343861000

C 1.262743000 3.294921000 -0.404932000

H 1.219121000 3.096725000 -1.483889000

H 0.392162000 2.803259000 0.049226000

H 1.164364000 4.376347000 -0.245351000

C 4.977884000 0.216883000 -0.167155000

H 5.743331000 0.984490000 0.044546000

H 5.396652000 -0.748653000 0.151867000

161


x y z

H 4.844920000 0.188558000 -1.254788000

C -3.885663000 2.391996000 0.951708000

H -4.238346000 3.293886000 0.440167000

H -4.624051000 2.150224000 1.727757000

H -2.936155000 2.630433000 1.441824000

C -2.492382000 3.487270000 -1.607586000

H -2.147643000 3.883915000 -0.646013000

H -2.032727000 4.091135000 -2.400141000

H -3.576013000 3.643270000 -1.674131000

C -0.967162000 -2.724974000 -1.908623000

H -0.665753000 -1.767243000 -2.351818000

H -0.104542000 -3.109353000 -1.351465000

H -1.198877000 -3.423330000 -2.722746000

C -1.013688000 -3.588612000 1.599279000

H -1.048780000 -4.009481000 2.611211000

H -1.289997000 -4.388892000 0.901145000

H 0.014850000 -3.274676000 1.393423000

H -2.399323000 1.613530000 3.493310000

H -1.696524000 -0.007339000 3.734414000

H -0.125851000 2.497853000 3.257538000

H 0.591061000 0.863542000 3.419569000

162


x y z

W 1.418610000 -0.520752000 -0.563087000

N -0.046852000 -1.064468000 -1.405080000

N 2.519806000 0.276834000 -2.038379000

N 3.189968000 1.413730000 0.809715000

N 1.889971000 -1.866736000 0.782909000

H 4.109195000 0.970132000 0.858919000

N 0.186980000 0.724677000 0.443188000

W -1.322164000 0.229958000 -0.421120000

N -2.366080000 -1.449858000 0.148015000

N -2.495235000 1.492143000 0.652120000

N -1.565120000 1.271646000 -2.096514000

C -3.631104000 -1.363395000 0.914652000

C -3.510586000 -1.695151000 2.405899000

H -3.898435000 -0.306957000 0.896037000

H -4.408235000 -1.339694000 2.931354000

H -3.417812000 -2.764173000 2.617995000

H -2.643281000 -1.186043000 2.844409000

C -1.898794000 -2.816472000 -0.219480000

C -2.404509000 -3.239384000 -1.596690000

H -0.813975000 -2.727508000 -0.313576000

H -1.902932000 -4.161141000 -1.922243000

163


x y z

H -3.484713000 -3.427013000 -1.611014000

H -2.175427000 -2.462319000 -2.335306000

C -3.840936000 1.970239000 0.284299000

C -3.944774000 3.493875000 0.183781000

H -4.529471000 1.653788000 1.089220000

H -4.942693000 3.772291000 -0.178522000

H -3.791914000 3.997495000 1.142573000

H -3.206843000 3.884995000 -0.527158000

C -2.025392000 1.919807000 2.001703000

C -1.177936000 3.188129000 1.924705000

H -1.343958000 1.123683000 2.332358000

H -0.674714000 3.372139000 2.884111000

H -0.404232000 3.049891000 1.161554000

H -1.767769000 4.077716000 1.677999000

C -1.985266000 0.646248000 -3.325701000

H -2.176996000 -0.422218000 -3.171182000

C -1.309104000 2.682204000 -2.231234000

H -1.058091000 3.119405000 -1.257999000

C 2.705244000 1.585345000 2.201542000

C 3.175589000 2.822976000 2.962560000

H 1.606003000 1.611469000 2.127119000

164


x y z

H 2.764535000 2.794458000 3.980065000

H 4.270032000 2.848954000 3.053436000

H 2.849372000 3.763667000 2.508671000

C 3.337730000 2.600279000 -0.067538000

C 4.560116000 3.474763000 0.214188000

H 3.496780000 2.166337000 -1.061161000

H 4.739233000 4.145181000 -0.636596000

H 4.456060000 4.102622000 1.104512000

H 5.464581000 2.863789000 0.339328000

C 3.928455000 0.124880000 -2.295630000

H 4.479704000 -0.018032000 -1.360607000

C 1.825097000 0.803194000 -3.196845000

H 0.758605000 0.927378000 -2.984573000

C 2.769865000 -2.208748000 -0.278732000

C 2.418283000 -3.441960000 -1.093996000

H 2.757680000 -4.370016000 -0.598909000

H 1.337126000 -3.530209000 -1.263845000

H 2.901622000 -3.416389000 -2.080160000

C 1.240906000 -2.789570000 1.703922000

C 2.296662000 -3.520753000 2.525589000

H 0.681235000 -3.550797000 1.124481000

165


x y z

H 1.824292000 -4.222947000 3.223621000

H 2.978259000 -4.090760000 1.883894000

H 2.896420000 -2.809702000 3.108969000

C 4.246329000 -2.134479000 0.048696000

H 4.564154000 -2.995188000 0.662330000

H 4.872181000 -2.146053000 -0.853525000

H 4.487730000 -1.229484000 0.623359000

C 0.265037000 -2.036727000 2.590145000

H 0.781455000 -1.246945000 3.151204000

H -0.526086000 -1.564289000 1.996344000

H -0.207904000 -2.714000000 3.313120000

C 3.117980000 0.346641000 2.980127000

H 2.643161000 0.327268000 3.968297000

H 2.845604000 -0.563716000 2.436546000

H 4.207312000 0.340934000 3.141146000

C 2.055541000 3.406058000 -0.165943000

H 2.156242000 4.164583000 -0.952250000

H 1.210678000 2.755783000 -0.414445000

H 1.808468000 3.931478000 0.764684000

C -3.117396000 2.013512000 3.060522000

H -2.650601000 2.170465000 4.040073000

166


x y z

H -3.811135000 2.847653000 2.898451000

H -3.705473000 1.089798000 3.121153000

C -4.372771000 1.363248000 -1.013226000

H -4.001441000 1.901163000 -1.892170000

H -4.104480000 0.305058000 -1.135410000

H -5.467741000 1.431087000 -1.023833000

C -4.813316000 -2.086174000 0.271034000

H -4.730130000 -3.177796000 0.301928000

H -5.736825000 -1.818477000 0.801823000

H -4.932207000 -1.790618000 -0.778735000

C -2.107840000 -3.933184000 0.798924000

H -1.593114000 -4.829356000 0.426955000

H -1.670914000 -3.688069000 1.772133000

H -3.155684000 -4.212909000 0.955323000

H 1.924913000 0.142625000 -4.077260000

H 2.235675000 1.791323000 -3.474232000

H 4.142789000 -0.740360000 -2.949005000

H 4.334706000 1.020391000 -2.797748000

H -1.214659000 0.733626000 -4.111816000

H -2.910648000 1.109917000 -3.712760000

H -0.475690000 2.886711000 -2.927175000

167


x y z

H -2.199317000 3.208501000 -2.626417000

Table C-6. Optimized Cartesian coordinates for iPr2NH in the decomposition pathway of 35.

x y z

N 0.103998000 -0.521078000 -0.745204000

H 0.286950000 -0.002939000 -1.602857000

C 1.125721000 -0.167949000 0.240162000

C 1.116732000 1.275234000 0.751405000

H 0.972530000 -0.834964000 1.102359000

H 1.987807000 1.472206000 1.390458000

H 1.153181000 1.986688000 -0.085935000

H 0.222992000 1.503263000 1.342738000

C -1.318089000 -0.392135000 -0.409727000

C -1.911758000 1.010276000 -0.563120000

H -1.839500000 -1.030070000 -1.143140000

H -3.006951000 0.978538000 -0.489717000

H -1.551965000 1.705824000 0.203413000

H -1.662964000 1.438957000 -1.542881000

C 2.478992000 -0.501835000 -0.370910000

H 3.290958000 -0.355054000 0.350708000

H 2.500960000 -1.538453000 -0.721700000

168


x y z

H 2.687923000 0.148767000 -1.232551000

C -1.608445000 -0.969205000 0.965408000

H -2.689609000 -1.039422000 1.129199000

H -1.180606000 -1.972671000 1.070705000

H -1.198611000 -0.339439000 1.766320000

Cartesian Coordinates for the Decomposition Pathway of 34

Table C-7. Optimized Cartesian coordinates for the GS in the decomposition pathway of 34.

x y z

W -0.067248000 -0.008064000 -0.388760000

N -1.642957000 1.105042000 0.045514000

N 1.671227000 0.819473000 0.061673000

N -0.171659000 -1.838228000 0.347255000

N -0.066992000 -0.217436000 -2.054591000

C 2.852748000 0.891692000 -0.789796000

C 3.396580000 2.292229000 -1.017971000

H 2.589163000 0.433133000 -1.749039000

H 3.646591000 0.262072000 -0.345381000

H 4.238798000 2.264688000 -1.719403000

H 2.623752000 2.947240000 -1.437495000

H 3.761922000 2.747306000 -0.088978000

C 1.846221000 1.332515000 1.420247000

169


x y z

C 1.387502000 2.771511000 1.608907000

H 2.903890000 1.219496000 1.714308000

H 1.283086000 0.689953000 2.122837000

H 1.456725000 3.072716000 2.661882000

H 1.985243000 3.470218000 1.014869000

H 0.344211000 2.883743000 1.287840000

C 0.016960000 -1.992262000 1.784124000

C 1.411680000 -2.449896000 2.182153000

H -0.738499000 -2.693113000 2.181764000

H -0.199353000 -1.024000000 2.270131000

H 1.523938000 -2.479391000 3.272907000

H 1.621417000 -3.455675000 1.799446000

H 2.170172000 -1.770320000 1.771013000

C -0.135663000 -3.086057000 -0.416293000

C 1.177390000 -3.312493000 -1.147708000

H -0.957400000 -3.073844000 -1.144658000

H -0.339129000 -3.921471000 0.274122000

H 1.163243000 -4.260480000 -1.700048000

H 1.345186000 -2.501647000 -1.866523000

H 2.027916000 -3.331998000 -0.455154000

C -2.655637000 1.599757000 -0.888243000

170


x y z

C -3.479328000 0.496765000 -1.531379000

H -2.153674000 2.179541000 -1.674017000

H -3.311296000 2.303495000 -0.349251000

H -4.217578000 0.911849000 -2.228815000

H -2.821595000 -0.177333000 -2.093004000

H -4.013770000 -0.098350000 -0.780816000

C -1.985039000 1.256309000 1.454900000

C -3.143460000 0.384137000 1.911937000

H -2.204567000 2.317869000 1.668069000

H -1.090505000 1.018093000 2.058478000

H -3.320696000 0.492170000 2.988959000

H -4.071144000 0.655455000 1.393974000

H -2.936772000 -0.671914000 1.695995000

Table C-8. Optimized Cartesian coordinates for TS1 in the decomposition pathway of 34.

x y z

N 0.443912000 2.004221000 0.078815000

W 0.008708000 -0.085868000 -0.357667000

N -1.806691000 -0.795339000 -0.033645000

N 0.174648000 -0.167704000 -2.026082000

N 1.310936000 -1.400007000 0.361043000

171


x y z

H 1.462511000 1.091542000 0.313619000

C 1.837406000 -2.549405000 -0.358527000

C 2.994940000 -3.203320000 0.372961000

H 2.150588000 -2.246834000 -1.376620000

H 1.013892000 -3.265440000 -0.484677000

H 3.334435000 -4.101736000 -0.155381000

H 3.850083000 -2.520015000 0.446742000

H 2.705273000 -3.489418000 1.390959000

C 2.155906000 -0.215661000 0.427971000

C 2.808119000 0.015890000 1.778718000

H 2.889886000 -0.179770000 -0.395841000

H 3.228148000 1.027358000 1.869399000

H 2.083320000 -0.128394000 2.588034000

H 3.626081000 -0.697082000 1.948549000

C 0.626403000 2.952789000 -1.019288000

C 1.846596000 2.650452000 -1.864634000

H 0.738542000 3.954205000 -0.569854000

H -0.272695000 2.999027000 -1.658848000

H 1.967411000 3.414856000 -2.639890000

H 2.755924000 2.646724000 -1.249423000

H 1.759329000 1.678411000 -2.361196000

172


x y z

C -0.298539000 2.536784000 1.212074000

C -0.051993000 1.753026000 2.487404000

H -1.384943000 2.573218000 0.994157000

H 0.008939000 3.583668000 1.373542000

H -0.710605000 2.095838000 3.292906000

H -0.239953000 0.674358000 2.360819000

H 0.986147000 1.860489000 2.819615000

C -2.728765000 -1.292105000 -1.057306000

C -4.097696000 -0.631451000 -1.069033000

H -2.853319000 -2.380314000 -0.914575000

H -2.240373000 -1.151446000 -2.026296000

H -4.658644000 -0.946709000 -1.956658000

H -4.699692000 -0.901427000 -0.194048000

H -4.005129000 0.461113000 -1.096431000

C -2.214490000 -1.096197000 1.343013000

C -3.063021000 -0.025795000 2.015284000

H -1.304454000 -1.263022000 1.942852000

H -2.749264000 -2.061222000 1.347989000

H -3.216278000 -0.265468000 3.074888000

H -2.571050000 0.952709000 1.960417000

H -4.047316000 0.080806000 1.549890000

173


x y z

N 1.458719000 1.741576000 0.074687000

W 0.116965000 -0.081230000 -0.323258000

N -1.838247000 0.316145000 -0.148052000

N 0.492323000 -0.346032000 -1.945481000

N 0.303099000 -1.855819000 0.581211000

H 2.069387000 1.461434000 0.844946000

C 0.328132000 -3.130519000 -0.112690000

C 0.747021000 -4.257816000 0.813669000

H 1.009841000 -3.078509000 -0.984181000

H -0.676687000 -3.321079000 -0.516155000

H 0.745541000 -5.222439000 0.291772000

H 1.759852000 -4.086937000 1.200345000

H 0.070544000 -4.329398000 1.673611000

C 1.542313000 -1.196787000 0.829980000

C 1.867484000 -0.864061000 2.267213000

H 2.398768000 -1.612135000 0.273248000

H 2.708110000 -0.154912000 2.346148000

H 1.004884000 -0.411439000 2.779943000

H 2.150219000 -1.750001000 2.858658000

C 2.347770000 2.099694000 -1.065115000

C 3.400714000 1.046755000 -1.313786000

174


x y z

H 2.815672000 3.072355000 -0.838280000

H 1.707162000 2.230953000 -1.944211000

H 4.079860000 1.381388000 -2.104851000

H 4.003622000 0.865370000 -0.413264000

H 2.940840000 0.103881000 -1.623202000

C 0.669376000 2.906737000 0.544516000

C 0.099346000 2.647521000 1.919175000

H -0.127470000 3.082997000 -0.190550000

H 1.312962000 3.801070000 0.550860000

H -0.521774000 3.485386000 2.250646000

H -0.530213000 1.749197000 1.917139000

H 0.893689000 2.501359000 2.662107000

C -2.754833000 0.485911000 -1.275928000

C -3.735984000 -0.661991000 -1.451554000

H -2.142864000 0.586354000 -2.177738000

H -3.311163000 1.434104000 -1.166138000

H -4.326268000 -0.525322000 -2.364731000

H -3.197988000 -1.614554000 -1.532317000

H -4.441167000 -0.741650000 -0.615194000

C -2.507225000 0.185010000 1.143355000

C -3.383994000 1.370151000 1.516299000

175


x y z

H -1.734645000 0.030639000 1.913235000

H -3.107220000 -0.740835000 1.163800000

H -3.759406000 1.273542000 2.541445000

H -2.826860000 2.313346000 1.441953000

H -4.254644000 1.452122000 0.854689000

Table C-10. Optimized Cartesian coordinates for TS2 in the decomposition pathway of 34.

x y z

W -1.468998000 0.370679000 -0.286809000

N -0.200253000 0.694177000 -1.438317000

N -2.754645000 -0.861979000 -1.220715000

N -2.366031000 -1.054159000 1.714990000

N -1.958830000 1.957696000 0.800361000

H -3.370636000 -1.170095000 1.586955000

N 0.178962000 -0.128320000 1.016900000

W 1.506537000 0.098824000 -0.105860000

N 2.174970000 1.952249000 -0.481111000

N 3.011972000 -0.388378000 1.106269000

N 1.740434000 -1.434619000 -1.346616000

C 3.604754000 2.240673000 -0.456663000

C 4.087809000 2.789728000 0.875739000

176


x y z

H 3.833844000 2.960817000 -1.260115000

H 4.177554000 1.336300000 -0.710624000

H 5.156749000 3.037282000 0.842400000

H 3.539484000 3.699976000 1.147459000

H 3.929689000 2.054635000 1.672898000

C 1.376700000 3.120486000 -0.828741000

C 1.353081000 3.385409000 -2.325394000

H 1.762419000 4.002094000 -0.285859000

H 0.354775000 2.959711000 -0.475912000

H 0.763766000 4.281968000 -2.557698000

H 2.362082000 3.540873000 -2.729157000

H 0.901484000 2.529632000 -2.839523000

C 4.303862000 -0.843623000 0.625905000

C 4.686867000 -2.238804000 1.093290000

H 5.090369000 -0.124156000 0.925529000

H 4.282052000 -0.830732000 -0.473757000

H 5.641523000 -2.546509000 0.649406000

H 4.800158000 -2.283791000 2.182815000

H 3.920048000 -2.966785000 0.801470000

C 2.911043000 -0.270197000 2.562482000

C 2.187939000 -1.433111000 3.223442000

177


x y z

H 2.380205000 0.661988000 2.806071000

H 3.927145000 -0.162013000 2.979705000

H 2.128924000 -1.288702000 4.309740000

H 1.165849000 -1.498262000 2.830536000

H 2.690904000 -2.388255000 3.031103000

C 2.420535000 -1.182676000 -2.607873000

C 3.433711000 -2.257549000 -2.969633000

H 2.925439000 -0.204185000 -2.538573000

H 1.673575000 -1.068401000 -3.415605000

H 3.915926000 -2.037127000 -3.929200000

H 4.213954000 -2.340083000 -2.202460000

H 2.956786000 -3.241587000 -3.058665000

C 0.854007000 -2.589551000 -1.327327000

C 1.170554000 -3.552790000 -0.199198000

H 0.897968000 -3.109310000 -2.298215000

H -0.188654000 -2.235808000 -1.224335000

H 0.427133000 -4.359651000 -0.146283000

H 2.161608000 -4.005279000 -0.329956000

H 1.167275000 -3.020881000 0.762643000

C -2.139366000 -0.371453000 2.999363000

C -2.502784000 -1.155596000 4.247425000

178


x y z

H -2.700915000 0.569024000 2.946578000

H -1.077448000 -0.092870000 3.012290000

H -2.335492000 -0.544110000 5.142029000

H -3.557342000 -1.462608000 4.249913000

H -1.889481000 -2.059353000 4.354794000

C -1.742019000 -2.388426000 1.604509000

C -2.663551000 -3.548786000 1.926429000

H -0.848227000 -2.392426000 2.241754000

H -1.377183000 -2.500007000 0.572897000

H -2.146968000 -4.505766000 1.781028000

H -3.032853000 -3.519870000 2.958274000

H -3.536179000 -3.550245000 1.258468000

C -4.165876000 -0.926823000 -0.858533000

C -5.125557000 -0.410969000 -1.921249000

H -4.308221000 -0.315755000 0.043508000

H -4.448742000 -1.960420000 -0.580496000

H -6.140773000 -0.338695000 -1.514364000

H -4.818880000 0.586560000 -2.259048000

H -5.170726000 -1.065843000 -2.799021000

C -2.456440000 -1.496821000 -2.503408000

C -2.677451000 -3.002143000 -2.476440000

179


x y z

H -1.413948000 -1.272784000 -2.753951000

H -3.062766000 -1.050271000 -3.310456000

H -2.375836000 -3.460744000 -3.425802000

H -2.092826000 -3.468516000 -1.670366000

H -3.731417000 -3.258398000 -2.307142000

C -2.752184000 2.073267000 -0.369593000

C -2.504498000 3.195121000 -1.350442000

H -3.832981000 1.893967000 -0.213836000

H -2.855681000 4.167634000 -0.966323000

H -1.439934000 3.296407000 -1.594682000

H -3.034814000 3.009925000 -2.293407000

C -1.372327000 3.051561000 1.533337000

C -2.374816000 3.678241000 2.490402000

H -0.991769000 3.837148000 0.854804000

H -0.501238000 2.665822000 2.084806000

H -1.932978000 4.521815000 3.035272000

H -3.250408000 4.051230000 1.944033000

H -2.731247000 2.944643000 3.223811000


x y z

W -1.700647000 0.042307000 -0.002392000

180


x y z

N -0.597301000 0.163464000 -1.361579000

N -2.749013000 -1.631163000 0.075156000

N -2.360590000 1.722502000 0.807254000

N -0.080439000 -0.049378000 1.215746000

W 1.170374000 0.030010000 -0.066663000

N 1.657366000 1.767753000 -0.918118000

N 2.720325000 0.018473000 1.201983000

N 1.715357000 -1.668880000 -0.926160000

C 3.065801000 2.112650000 -1.081392000

C 3.599077000 3.022811000 0.012687000

H 3.198716000 2.591939000 -2.065976000

H 3.669832000 1.193064000 -1.123994000

H 4.647841000 3.289093000 -0.170226000

H 3.020699000 3.952944000 0.068591000

H 3.534161000 2.530627000 0.989940000

C 0.754359000 2.790687000 -1.431273000

C 0.602839000 2.729096000 -2.942145000

H 1.116383000 3.785209000 -1.117337000

H -0.225943000 2.653044000 -0.964734000

H -0.060335000 3.526295000 -3.301009000

H 1.566932000 2.846021000 -3.453835000

181


x y z

H 0.171672000 1.764048000 -3.229102000

C 4.065198000 -0.422200000 0.864338000

C 4.647339000 -1.463399000 1.808260000

H 4.744251000 0.452247000 0.826526000

H 4.036652000 -0.837454000 -0.152059000

H 5.635473000 -1.782786000 1.455969000

H 4.771167000 -1.073163000 2.824987000

H 4.001952000 -2.349266000 1.862370000

C 2.608572000 0.594365000 2.548366000

C 2.056948000 -0.374545000 3.580621000

H 1.951004000 1.473852000 2.499842000

H 3.599729000 0.968578000 2.858689000

H 1.983604000 0.109275000 4.562467000

H 1.053724000 -0.698163000 3.283684000

H 2.692091000 -1.261572000 3.685341000

C 2.011156000 -1.567062000 -2.353286000

C 3.345918000 -2.168833000 -2.760398000

H 1.978931000 -0.503724000 -2.636052000

H 1.188043000 -2.043946000 -2.917682000

H 3.518934000 -2.025907000 -3.832904000

H 4.175471000 -1.696181000 -2.218975000

182


x y z

H 3.387781000 -3.245712000 -2.560896000

C 1.657611000 -3.030789000 -0.426692000

C 1.023971000 -3.147369000 0.942710000

H 2.679536000 -3.452176000 -0.396422000

H 1.099909000 -3.652345000 -1.153526000

H 1.024793000 -4.192739000 1.272783000

H 1.567186000 -2.550524000 1.685484000

H -0.011577000 -2.785560000 0.937423000

C -3.914585000 -1.728887000 0.950164000

C -5.229525000 -1.865010000 0.200127000

H -3.938498000 -0.821837000 1.571938000

H -3.789854000 -2.571087000 1.651391000

H -6.076264000 -1.831575000 0.894823000

H -5.344641000 -1.050066000 -0.524654000

H -5.291685000 -2.813261000 -0.348022000

C -2.573117000 -2.744367000 -0.857775000

C -2.530049000 -4.108967000 -0.189045000

H -1.639103000 -2.565018000 -1.406306000

H -3.379612000 -2.733217000 -1.611015000

H -2.294076000 -4.885719000 -0.925467000

H -1.768454000 -4.142503000 0.599103000

183


x y z

H -3.492526000 -4.372621000 0.266422000

C -3.263366000 1.495494000 -0.267589000

C -3.260849000 2.430530000 -1.453884000

H -4.281311000 1.210837000 0.047458000

H -3.687549000 3.418027000 -1.210975000

H -2.246220000 2.594805000 -1.841545000

H -3.855995000 2.015456000 -2.276214000

C -1.841241000 3.011940000 1.199922000

C -2.801528000 3.723190000 2.139150000

H -1.652323000 3.654299000 0.320866000

H -0.869348000 2.851103000 1.689960000

H -2.412950000 4.705015000 2.436577000

H -3.774379000 3.876984000 1.655497000

H -2.970732000 3.128476000 3.043731000

Table C-12. Optimized Cartesian coordinates for Et2NH in the decomposition pathway of 34.

x y z

N 0.018477000 -1.012182000 -0.355004000

H -0.122257000 -0.811628000 -1.341918000

C 1.329226000 -0.534764000 0.058437000

C 1.569939000 0.971490000 0.045945000

H 2.069502000 -1.029495000 -0.585322000

184


x y z

H 1.511687000 -0.920891000 1.072394000

H 2.606917000 1.208885000 0.315158000

H 1.377140000 1.399350000 -0.946902000

H 0.920179000 1.489575000 0.762249000

C -1.113809000 -0.498779000 0.409837000

C -1.780182000 0.751345000 -0.149279000

H -0.764785000 -0.315879000 1.436589000

H -1.872327000 -1.293190000 0.491370000

H -2.648974000 1.045515000 0.453021000

H -1.094037000 1.605119000 -0.190947000

H -2.143435000 0.572161000 -1.170308000

Cartesian Coordinates for Cu2S and SnS2

Table C-13. Optimized Cartesian coordinates for Cu2S using M06L/LANL2DZ

x y z

S -1.343593000 -0.418388000 0.000000000

Cu 0.741293000 -1.073332000 0.000000000

Cu 0.000000000 1.304167000 0.000000000

185

Table C-14. Optimized Cartesian coordinates for SnS2 using B3LYP/LANL2DZ

x y z

Sn -0.000010000 -0.000125000 0.000000000

S 2.258008000 0.000195000 0.000000000

S -2.257979000 0.000195000 0.000000000

Cartesian Coordinates for SnSe2

Table C-15. Optimized Cartesian coordinates for SnSe2 using B3LYP/LANL2DZ

x y z

Sn 0.000000000 1.330905000 0.000000000

Se 1.317182000 -0.978394000 0.000000000

Se -1.317182000 -0.978819000 0.000000000

Table C-16. Optimized Cartesian coordinates for SnSe2 using M06L/LANL2DZ

x y z

Sn 0.000000000 0.000027000 0.000000000

Se 2.389902000 0.063093000 0.000000000

Se -2.389902000 -0.063133000 0.000000000

Cartesian Coordinates for Cu3Sn and Cu3Zn

Table C-17. Optimized Cartesian coordinates for Cu3Sn using B3LYP/LANL2DZ

x y z

Sn 0.000428000 0.000375000 -0.493676000

186


x y z

Cu -1.666878000 1.677290000 0.283708000

Cu -0.620667000 -2.281345000 0.283543000

Cu 2.286807000 0.603409000 0.283914000

Table C-18. Optimized Cartesian coordinates for Cu3Sn using M06L/LANL2DZ

x y z

Sn 0.077425000 1.121361000 0.050323000

Cu 2.120603000 0.336949000 0.092941000

Cu 0.134676000 1.420167000 0.102516000

Cu 2.119419000 0.176265000 0.096338000

Table C-19. Optimized Cartesian coordinates for Cu3Zn using M06L/LANL2DZ

x y z

Zn -0.486643000 0.000016000 -0.000659000

Cu -2.816502000 -0.000001000 0.000327000

Cu 1.659949000 -1.203326000 0.000178000

Cu 1.659977000 1.203310000 0.000178000

187

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BIOGRAPHICAL SKETCH

Arijit Koley was born in 1986, in West Bengal, India. He has always shown a keen

interest in science. His passion for chemistry started during his high school years because he felt

that in chemistry he can get answers at a molecular level. He followed his thrust in chemistry in

his undergraduate studies at R.K.M.V.C.C. in Kolkata where he learned the basics of chemistry

in a more intense form. He continued his studies by doing a master’s degree at IIT Kharagpur

where he was introduced to the broader aspects of chemistry. Challenging synthesis and wide

applications of organometallic chemistry intrigued him to undergo higher studies. He followed

his interest to pursue a PhD in University of Florida under the supervision of Prof. Lisa

McElwee-White where he synthesized organometallic precursors for applications in

semiconductor industry. He received his PhD from the University of Florida in the summer of

2016.

synthesis of organometallic precursors for wnxcy...

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