[inorganic syntheses] inorganic syntheses (rauchfuss/inorganic syntheses v. 35) || organometallic...

Chapter Six

ORGANOMETALLIC REAGENTS

27. TRICARBONYL 1,3,5-TRIMETHYL-1,3,5-TRIAZACYCLOHEXANE COMPLEXES OF CHROMIUM(0),MOLYBDENUM(0), AND TUNGSTEN(0) [M(CO)3(Me3TACH)

(M ¼ Cr, Mo, W)]

Submitted by NICOLE L. ARMANASCO,� MURRAY V. BAKER,�

ALISON G. BARNES,� DAVID H. BROWN,� VALERIE J. HESLER,� andMICHAEL R. NORTH�

Checked by DAMON LEE, MICHAEL J. PAROLINE, and

THOMAS B. RAUCHFUSS�

1,3,5-Triazacyclohexanes (R3TACH) typically serve as tripodal ligands. The first

reported complexes of a group VI metal (Cr, Mo, W) tricarbonyl with a R3TACH

were the chromium andmolybdenum complexes fac-M(CO)3(R3TACH) (M¼Cr,

Mo; R ¼ Me, Et, Cy), prepared from the metal hexacarbonyls M(CO)6 (M ¼ Cr,

Mo) in refluxing dibutyl ether, and in one case from Mo(CO)3(py)3 (py ¼pyridine), although no yield was specified.1 The complexes fac-Mo(CO)3(R3TACH) (R ¼ Me, Pri, Bn) were isolated in excellent yields (89–95%) by the

reaction of Mo(CO)3(h6-cycloheptatriene) with the corresponding triazacyclo-

hexane.2 The applicability of this method to the synthesis of chromium or tungsten

analogues has not been reported; however, the reported yield of W(CO)3(h6-

cycloheptatriene) fromW(CO)6 is low. Since these reports, fac-M(CO)3(R3TACH)

Inorganic Syntheses, Volume 35, edited by Thomas B. RauchfussCopyright � 2010 John Wiley & Sons, Inc.

*Chemistry M313, School of Biomedical, Biomolecular and Chemical Sciences, The University of

Western Australia, Crawley, WA 6009, Australia .�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

109

(M¼ Cr, Mo,W) complexes have been prepared fromM(CO)6 (M¼ Cr, Mo, W),

M(CO)3(CH3CN)3 (M ¼ Cr, W), and M(CO)3(CH3CH2CN)3 (M ¼ Cr, Mo).3–7

In the case of the nitrile precursors, complete formation of the tris(nitrile)

complexes M(CO)3(RCN)3 (R ¼ Me, Et) is not required and the reaction of

R3TACH with M(CO)6�n(RCN)n (n ¼ 2 or 3) will afford the TACH complex

fac-M(CO)3(R3TACH).

Of synthetic utility are the complexes of 1,3,5-trimethyl-1,3,5-triazacyclo-

hexane (Me3TACH), fac-M(CO)3(Me3TACH) (M ¼ Cr, Mo, W). 1,3,5-Triaza-

cyclohexanes (TACH) are the smallest members of the triazacycloalkane family.

The small ring size results in significant strain in triazacyclohexane complexes.

In the case of fac-M(CO)3(Me3TACH) (M ¼ Cr, Mo, W), the Me3TACH ligands

are labile, and these complexes can serve as convenient sources of the fac-

M(CO)3 fragment without the need for thermal or photochemical activation. For

example, treatment of fac-M(CO)3(Me3TACH) (M ¼ Cr, Mo, W) with phos-

phines at room temperature affords tris(phosphine) complexes rapidly, exclu-

sively with a fac-M(CO)3 fragment, though sterically hindered phosphines and

phosphines with additional donor groups can afford different products.3–5,8–10

Dissolution of fac-Cr(CO)3(Me3TACH) in pyridine rapidly affords fac-

Cr(CO)3(py)3 while treatment with 1 equiv of fac-Cr(CO)3(Me3TACH) with tris

(3,5-dimethylpyrazol-1-yl)methane [(3,5-Me2pz)3CH] affords fac-Cr(CO)3[(3,5-

Me2pz)3CH].4 Dissolution of the tungsten and molybdenum complexes

fac-M(CO)3(Me3TACH) (M¼Mo, W) in acetonitrile at room temperature affords

exclusively fac-M(CO)3(CH3CN)3 (M ¼Mo, W), which can be readily isolated

in analytically pure forms.5 In contrast, when prepared by the standard method

(heating themetal hexacarbonyl in acetonitrile at reflux for an extended period of

time), the tris(nitrile) complexes fac-M(CO)3(CH3CN)3 can be contaminated

with bis(nitrile) complexes M(CO)4(CH3CN)2. The tungsten complex fac-

W(CO)3(Me3TACH) can react with alkynes to afford W(CO)(h2-RC�CR)3.5

The molybdenum and tungsten complexes are more labile than the chromium

analogue.

Starting Materials

Technical grade metal hexacarbonyls (96–98%) are suitable. While 1,3,5-

trimethyl-1,3,5-triazacyclohexane (1,3,5-trimethylhexahydro-1,3,5-triazine) is

commercially available, it is also conveniently prepared from aqueous methyl-

amine and aqueous formaldehyde solution or paraformaldehyde following the

method of Graymore and purified by distillation (60–61�C at 12mmHg).11

& Caution. The metal hexacarbonyls (volatile solids) and CO gas

are toxic. All operations should be performed in a well-ventilated fume

hood.

110 Organometallic Reagents

A. TRICARBONYL(1,3,5-TRIMETHYL-1,3,5-

TRIAZACYCLOHEXANE)CHROMIUM(0), fac-Cr(CO)3(Me3TACH)

CrðCOÞ6 þMe3TACH!CrðCOÞ3ðMe3TACHÞþ 3CO

Procedure

1,3,5-Trimethyl-1,3,5-triazacyclohexane (2.1 g, 16mmol) is added to xylenes

(40mL) in a 50-mL Schlenk flask equipped with a magnetic stirrer bar. The

solution is degassed by at least three freeze–pump–thaw cycles. Chromium

hexacarbonyl (1.6 g, 7.3mmol) is quickly added to the solution under a stream

of nitrogen. A Liebig condenser, the top of which is connected to a nitrogen

supply and a bubbler (to allow escape of CO), is fitted to the Schlenk flask. The

flask is heated so that the solvent refluxes vigorously until Cr(CO)6 no longer

sublimes from the reaction mixture (ca. 24 h). In all three preparations, the metal

hexacarbonyl tends to sublime into the condenser. Typically, if the reaction

temperature is initially raised slowly and then, once the reaction mixture is at

reflux, it is allowed to reflux vigorously, the solvent washes the sublimed material

back into the reaction mixture. As the reaction proceeds, the amount of sublimed

material decreases. Alternatively, the reaction flask can be removed from the heat,

and then under a blanket of nitrogen, a long spatula can be used to dislodge the

sublimed material back into the reaction mixture. It may be necessary to repeat

this process a number of times. Similar methods (swirling the reaction flask to

dislodge sublimed material, allowing solvent to wash down the metal hexacar-

bonyl, scraping the metal hexacarbonyl off the condenser wall, and/or slow heat

ramping) have been suggested by other researchers working with group VI

hexacarbonyls.12–14

As the reaction proceeds, an orange precipitate forms. While the mixture is

warm, the precipitate is collected under nitrogen, most conveniently using a small

Schlenk filter with a porosity-3 glass frit. The product is transferred to an inert

atmosphere glovebox. The orange crystalline solid is washed with hexane (2 �20mL), ethyl acetate (2 � 20mL), and hexane (2 � 20mL), and is then dried

in vacuo to afford Cr(CO)3(Me3TACH). Yield: 1.6 g (80%).

Anal. Calcd. for C9H15N3O3Cr: C, 40.76; H, 5.70; N, 15.84. Found: C, 40.59;

H, 5.55; N, 15.74. mp >240�C (decomp.). IR (Nujol) 1907, 1760 (br) (CO). Mass

spectrum: m/z 266.0601 (M þ H) (requires 266.0597). 1H NMR (acetone-d6):

d 2.49 (9H, s, 3�NCH3), 4.02 (3H, apparent d, splitting 8.3Hz, 3�NCHHN) and

4.66 (3H, apparent d, splitting 8.3Hz, 3 � NCHHN); 13C NMR (acetone-d6):

d 42.4 (CH3), 83.2 (NCH2N), and 237.5 (CO).

27. Tricarbonyl 1,3,5-Trimethyl-1,3,5-Triazacyclohexane 111

Properties

Tricarbonyl(1,3,5-trimethyl-1,3,5-triazacyclohexane)chromium(0) is an orange

crystalline, air-sensitive solid. On exposure to air, solid samples show visible

signs of decomposition within 30min. NMR solvents must be rigorously

degassed. Under an inert atmosphere, the complex is stable indefinitely in the

solid state. The complex is insoluble in nonpolar solvents but slightly soluble in

polar solvents (<0.4mg/mL in THF and ca. 19mg/mL in DMSO). Unlike the

molybdenum and tungsten analogues, Cr(CO)3(Me3TACH) does not undergo

solvolysis in DMSO.1H NMR spectroscopy is a diagnostic tool for the analysis of products. Signals

for the methylene protons of the conformationally rigid triazacyclohexane ring

appear as two apparent doublets (an AA0A00XX0X00 spin system), one for the three

axial protons and one for the three equatorial protons. In the 1H NMR spectrum

of free Me3TACH, the methylene protons appear as a very broad singlet, a

consequence of the fluxional nature of the free TACH ring system.15

B. TRICARBONYL(1,3,5-TRIMETHYL-1,3,5-TRIAZA-

CYCLOHEXANE)MOLYBDENUM(0), fac-Mo(CO)3(Me3TACH)

MoðCOÞ6 þMe3TACH!MoðCOÞ3ðMe3TACHÞþ 3CO

Procedure

The synthesis is similar to that for the chromium complex, using 1,3,5-trimethyl-

1,3,5-triazacyclohexane (2.1 g, 16mmol), molybdenum hexacarbonyl (1.86 g,

7.0mmol), and xylenes (30mL, mixture of isomers). The mixture is heated so

that the solvent refluxes vigorously for 3 h. The product is obtained as a yellow

powder (1.9 g, 88%).

Anal. Calcd. for C9H15N3O3Mo: C, 34.9; H, 4.9; N, 13.6. Found: C, 34.9; H, 5.1; N,

13.7. mp >200�C (decomp.). IR (KBr): 1900, 1785 (sh), 1750 (CO). 1H NMR

(acetone-d6): d 2.51 (9H, s, 3�NCH3), 4.08 (3H, apparent d, splitting 8.8 Hz, 3�NCHHN), and 4.70 (3H, apparent d, splitting 8.8 Hz, 3 � NCHHN). 13C NMR

(acetone-d6): d 42.4 (CH3), 83.3 (NCH2N), and 232.55 (CO).

Properties

Tricarbonyl(1,3,5-trimethyl-1,3,5-triazacyclohexane)molybdenum(0) is a yellow

air-sensitive compound. Exposure of the solid to air produces a dark brown solid

and Mo(CO)6. Under an inert atmosphere, the complex is stable indefinitely in the

solid state. The complex is insoluble in nonpolar solvents but sparingly soluble in


polar solvents such as acetone. Dissolution of the complex in DMSO rapidly

affords the solvolysis product Mo(CO)3(DMSO)3. The1H NMR spectrum can be

analyzed as described above for the Cr complex.

C. TRICARBONYL(1,3,5-TRIMETHYL-1,3,5-

TRIAZACYCLOHEXANE)TUNGSTEN(0), fac-W(CO)3(Me3TACH)

WðCOÞ6 þMe3TACH!WðCOÞ3ðMe3TACHÞþ 3CO

Procedure

The tungsten complex was prepared in 73% yield in a manner similar to the

chromium and molybdenum complexes.

Anal. Calcd. for C9H15N3O3W: C, 27.2; H, 3.8; N, 10.6. Found: C, 26.8; H, 3.8; N,

10.8.mp>190�C (decomp.). 1H NMR(acetone-d6): d 2.61 (9H, s, 3�NCH3), 4.91

(3H, apparent d, splitting 8.5Hz, with unresolved fine structure, 3�NCHHN), and

5.06 (3H, apparent d, splitting 8.5 Hz, with unresolved fine structure, 3 �NCHHN). 13C NMR (acetone-d6): d 42.9 (CH3), 83.5 (NCH2N), and 226.0 (CO).

IR (KBr): 1895, 1772 (sh), 1740 (CO).

Properties

W(CO)3(Me3TACH) is a yellow-tan air-sensitive compound. It also forms at lower

temperatures by the reaction ofMe3TACHwithW(CO)3(RCN)3 (R¼Me or Et) in

THF, and in these cases, the isolated complex is bright yellow. Spectroscopic

analysis indicates no appreciable differences between the products prepared by the

different methods. Exposure of the solid to air produces a dark brown solid and

W(CO)6. Under an inert atmosphere, the complex is stable indefinitely in the solid

state. The complex is insoluble in nonpolar solvents and only sparingly soluble in

polar solvents (ca. 0.05mg/mL in acetone). Dissolution of the complex in DMSO

rapidly affords the solvolysis product W(CO)3(DMSO)3. The1H NMR spectrum

can be analyzed as described above for the Cr complex.

References

1. A. L€uttringhaus and W. Kullick, Tetrahedron Lett. (10), 13 (1959).

2. H. Schumann, Z. Naturforsch. B 50, 1038 (1995).

3. N. L. Armanasco,M.V. Baker,M. R. North, B.W. Skelton, andA. H.White, J. Chem. Soc., Dalton

Trans. 1145 (1998).

4. N. L. Armanasco,M.V. Baker,M. R. North, B.W. Skelton, andA. H.White, J. Chem. Soc., Dalton

Trans. 1363 (1997).

27. Tricarbonyl 1,3,5-Trimethyl-1,3,5-Triazacyclohexane 113

5. M. V. Baker and M. R. North, J. Organomet. Chem. 565, 225 (1998).

6. M.V.Baker,D.H.Brown,B.W. Skelton, andA.H.White, J.Chem. Soc., Dalton Trans. 763 (2000).

7. M. V. Baker, D. H. Brown, B. W. Skelton, and A. H. White, J. Chem. Soc., Dalton Trans. 1483

(1999).

8. W.-Y. Yeh, S.-M. Peng, and G.-H. Lee, J. Organomet. Chem. 671, 145 (2003).

9. W.-Y. Yeh, C.-S. Lin, S.-M. Peng, and G.-H. Lee, Organometallics 23, 917 (2004).

10. N. Kuhn, M. Gohner, and M. Steimann, Z. Naturforsch. 56b, 95 (2001).

11. J. Graymore, J. Chem. Soc. 134, 1490 (1931).

12. K. R. Birdwhistell, Inorg. Synth. 29, 141 (1992).

13. A. R. Manning, P. Hackett, R. Birdwhistell, and P. Soye, Inorg. Synth. 28, 148 (1990).

14. G. J. Kubas and L. S. Van der Sluys, Inorg. Synth. 28, 29 (1990).

15. C. H. Bushweller, M. Z. Lourandos, and J. A. Brunelle, J. Am. Chem. Soc. 96, 1591 (1974).

28. MANGANESE TRICARBONYL TRANSFER(MTT) AGENTS

Submitted by SANG BOK KIM,� SIMON LOTZ,�

SHOUHENG SUN,� YOUNG KEUN CHUNG,z ROBERT D. PIKE,§ and

DWIGHT A. SWEIGART�

Checked by MARIA E. CARROLL,# DIDIER MORVAN,#

and THOMAS B. RAUCHFUSS#

The complexes [Mn(h6-arene)(CO)3]þ are isoelectronicwith [Cr(h6-arene)(CO)3]

and, as is the case with the chromium complexes, can be synthesized with a wide

variety of arenes.1 Functionalized arene ligands are of particular importance

because [Mn(arene)(CO)3]þ undergoes high-yield regio- and stereoselective attack

by a wide range of nucleophiles.2 A number of methods are available to make

p-arene tricarbonyl complexes of manganese(I), and the one selected is often

determined by the nature of the arene ring to be coordinated, which can have

substituents that are electron donating, electron withdrawing, or sterically

demanding.3 Condensed polyaromatic hydrocarbons such as naphthalene and

heterocyclic fused ring systems such as indole, benzofuran, and benzothiophene

can also p-bond in a h6-manner to manganese(I) tricarbonyl. Analogously, the

heteroaromatic five-membered thiophene ring can p-bond in a h5-fashion and

thereby donate six electrons.

*Department of Chemistry, Brown University, Providence, RI 02912.�Department of Chemistry, University of Pretoria, Pretoria 0002, South Africa .zDepartment of Chemistry, Seoul National University, Seoul 151-742, Korea .§Department of Chemistry, College of William and Mary, Williamsburg, VA 23187.#Department of Chemistry, University of Illinois at Urbana-Champaign,

Urbana, IL 61801.


Most methods to prepare [Mn(arene)(CO)3]þ make use of the abstraction of

the halogen from [Mn(CO)5X] (X ¼ halogen) by Lewis acids such as AlCl3(referred to as the Fischer–Hafner method)4 or by precipitation of silver(I) halide

(referred to as the silver method).5 The [Mn(CO)5]þ species can also be

generated via other indirect methods, most notably using dimanganese dec-

acarbonyl and trifluoroacetic anhydride in acidic medium.6 Coordination of the

arene rings is often achieved under harsh thermal conditions by refluxing in

appropriate solvents, with concomitant substitution for several carbonyl ligands.

The very popular silver method involves using silver(I) salts with weakly

coordinating anions such as perchlorate,7 triflate,8 or tetrafluoroborate9 and is

the method of choice for arenes with high sensitivity to acid. The silver method

uses milder reaction conditions in comparison to the Fischer–Hafner or tri-

fluoroacetic anhydride (TFA) procedures. The advantages and scope of these

different methods have been discussed by Pike and coworkers.3 It should be

noted that the synthesis of [Mn(arene)(CO)3]þ complexes starting from

[Mn(CO)5X] is often problematic when the arene contains electron-withdrawing

substituents. However, in recent significant work, it has been shown that access

to such electron-deficient systems is possible via the palladium-catalyzed

substitution for chloride in (h5-chlorocyclohexadienyl)Mn(CO)3, followed by

hydride abstraction.10

A synthetic strategy conceptually different from the ones that start with

Mn(CO)5X involves the initial generation of an intermediate arene manganese

tricarbonyl complex that has an arene ring sufficiently labile that it can be easily

replaced by reaction with a second arene. This method can also be seen as

transferring a Mn(CO)3þ fragment from one arene ligand to another (Eq. 1).

Studies of the stability of p-arene manganese tricarbonyl complexes with polycy-

clic condensed arenes (‘‘polyarenes’’) indicated that these compounds were

ideally suited to act as Mn(CO)3þ transfer reagents (MTT reagents).11 It was

observed that the polyarene complexes undergo ring slippage processes much

more readily than do the monocyclic analogues, which has been ascribed to a

smaller loss in resonance energy that accompanies the h6 ! h4 transformation in

the polyarene cases. Facile ring slippage is the requirement for the reaction shown

in Eq. 1 to be useful, and a series of [Mn(h6-polyarene)(CO)3]þ complexes have

been tested for their ability to effectively transfer the Mn(CO)3þ fragment in this

manner. A key feature of the synthesis of [Mn(arene)(CO)3]þ viaMTT reagents is

the very mild conditions—simply warming the reactants in dichloromethane

solvent (see below). The MTT reagents of choice contain a readily displaceable

naphthalene or acenaphthene ligand (Fig. 1). Both have been used with success

and both are quite stable thermally as solids or in solution in the absence of

nucleophilic reagents. The MTT method for the synthesis of [Mn(arene)(CO)3]þ

complexes often translates into an improved yield or a cleaner reaction product in

comparison to that afforded by other synthetic methods.11

28. Manganese Tricarbonyl Transfer (MTT) Agents 115

½Mnðarene0ÞðCOÞ3�þ þ arene!½MnðareneÞðCOÞ3�þ þ arene0

ðarene0 ¼ labile arene ligandÞ ð1Þ

Herein, an example is given of how the MTT method can be used to coordinate

Mn(CO)3þ to a p-molecule. Figure 2 gives examples of such p-systems. Thus,Mn

(CO)3þ can be coordinated to redox-active hydroquinones,12 sterically encum-

bered aromatics, and the curved (convex) face of centropolyindanes.13 Coordina-

tion tometal complexes containing a free arene or thiophene ring affords binuclear

systems useful in construction of nonlinear optical materials.14 It has been shown

that chiral metallocenes can react with MTT reagents by the transfer of a

cyclopentadienyl ring to generate planar chiral (cyclopentadienyl)Mn(CO)3 com-

plexes with high stereoselectivity.15 Alternatively, MTT reagents can transfer the

Mn(CO)3þ unit to metallocenes without Cp ring cleavage, resulting in novel

Figure 2. Examples of molecules that react with MTT reagents by p-coordination of the

Mn(CO)3þ unit.

Figure 1. Mn(h6-polyarene)(CO)3þ complexes that function as excellent MTT reagents.


bimetallic multidecker systems capped by the manganese tricarbonyl fragment.15

For each of the representative compounds shown below, the MTT method affords

products that can be obtained only in lower yields or cannot be obtained at all by

the other synthetic methods for the coordination of Mn(CO)3þ .

A. ACENAPHTHENE(TRICARBONYL)MANGANESE(I)*

MnðCOÞ5BrþAgBF4 !MnðCOÞ5BF4 þAgBr

MnðCOÞ5BF4 þC12H10 !½MnðC12H10ÞðCOÞ3�BF4 þ 2CO

Procedure

Under an atmosphere of nitrogen, a 250-mL two-necked flask is charged with Mn

(CO)5Br16 (1.10 g, 4.0mmol) along with a Teflon-coated stirring bar. Dichlor-

omethane (50mL, Fisher HPLC Grade D143-1) is added, and the solution stirred

until all the [Mn(CO)5Br] dissolves. The flask is covered with aluminum foil to

exclude light, and silver tetrafluoroborate is added (0.82 g, 4.2mmol). After

stirring the solution for 20min, a solution of acenaphthene (0.93 g, 6.0mmol)

in 10mL dichloromethane is added. The reaction mixture is refluxed for 3–4 h.

After being cooled to room temperature, the reaction mixture is filtered through a

Celite plug into a flask containing 250mL diethyl ether while stirring vigorously.

The Celite removes AgBr together with some undissolved product. The residue on

the Celite is washed with small portions (3 � 10mL) of dichloromethane, which

are collected separately, concentrated, and added dropwise to the stirred ether

solution. The product separates as a fine yellow solid. The yellow powder is

filtered off, washed with diethyl ether, and dried in vacuo. Although normally

quite pure at this stage, the solid can be further purified by redissolving in a

minimum of dichloromethane and treating as before by adding the solution in a

dropwise manner to a stirred solution of diethyl ether (250mL). Yield: 1.32 g

(3.48mmol, 87%).

Anal. Calcd (%): C, 47.37; H, 2.63. IR (CH2Cl2): 2072, 2012 cm�1. Found (%): C,

47.23; H, 2.72. 1H NMR (CD2Cl2): d 8.07 (m, H6), 7.90–7.75 (m, H5,7), 7.17 (d, J

¼ 7Hz, H4), 6.75 (m, H3), 6.58 (d, J ¼ 6Hz, H2), 3.90–3.60 (m, H9,10).

* Checkers obtainedyields about 30% lower than reported probablybecause of incomplete precipitation

of the products from the dichloromethane reaction solution. After the addition of the arene, the reaction

of Mn(CO)5Br with AgBF4 was monitored by IR spectroscopy. In some reactions, it was found that

additional AgBF4 (up to 20%) was required to completely convert all Mn(CO)5Br.


Properties

Acenaphthene(tricarbonyl)manganese(I) tetrafluoroborate11 is a light yellow solid

(mp 130�C decomp.) and is best kept under inert atmosphere to avoid contact with

moisture, with which it reacts to liberate the coordinated acenaphthene. Similarly,

it reacts rapidly with nucleophilic solvents such as acetonitrile and DMSO but is

highly soluble and stable in CH2Cl2. It is insoluble in ether and aromatic or

aliphatic hydrocarbons. The acenaphthene complex [Mn(h6-C12H10)(CO)3]BF4 is

the MTT reagent of choice in terms of cost, ease of synthesis, and shelf life.

B. NAPHTHALENE(TRICARBONYL)MANGANESE(I)

MnðCOÞ5BrþAgBF4 !MnðCOÞ5BF4 þAgBr

MnðCOÞ5BF4 þC10H8 !½MnðC10H8ÞðCOÞ3�BF4 þ 2CO

Procedure

The complex was prepared from Mn(CO)5Br16 (1.10 g, 4.0mmol), silver tetra-

fluoroborate (0.82 g, 4.2mmol), and naphthalene (0.77 g, 6.0mmol) by a proce-

dure analogous to that employed for the acenaphthene analogue. The product, a

pale yellow solid, was again isolated by filtration, washed with ether, and dried in

vacuo. Yield: 1.22 g (3.44mmol, 86%).

Anal. Calcd (%): C, 44.11; H, 2.28. Found (%): C, 43.87; H, 2.30. IR (CH2Cl2):

2077, 2022 cm�1. 1H NMR (CD2Cl2): d 8.06 (s, H5–8), 7.50–7.35 (m, H1,4),

6.80–6.65 (m, H2,3).

Properties

Naphthalene(tricarbonyl)manganese(I) tetrafluoroborate11 is a pale yellow solid

(mp 108�C decomp.). It is best kept under inert atmosphere due to its moisture

sensitivity. It dissolves readily in CH2Cl2 but is insoluble in ether and aromatic or

aliphatic hydrocarbons. As a MTT reagent, the naphthalene complex undergoes

arene substitution faster than theacenaphthene(tricarbonyl)manganese(I) analogue.

C. SYNTHESIS OF h6-N,N-DIMETHYLANILINE(TRICARBONYL)-MANGANESE(I) TETRAFLUOROBORATE,

[Mn(h6-C6H5NMe2)(CO)3]BF4

½MnðC12H10ÞðCOÞ3�BF4þC6H5NMe2!½MnðC6H5NMe2ÞðCOÞ3�F4þC12H10


Procedure

& Caution. The procedure involves heating a dichloromethane solution to

70�C, thus generating up to several atmospheres pressure. For this reason, the

experimental apparatus should be placed behind an appropriate protective shield.

A 30-mL pressure tube was flame dried under nitrogen and charged with [Mn(h6-

C12H10)(CO)3]BF4 (0.21 g, 0.55mmol) and N,N-dimethylaniline (1.40mL,

1.10mmol) dissolved in 20mL dichloromethane. N,N-Dimethylaniline was dried

prior to use with 4A�molecular sieves. The tube was sealed, heated in a silicon oil

bath at 75�C for 3 h, and then cooled to room temperature. After evaporation to ca.

5mL, this solution was added slowly to 100mL of diethyl ether through a plug of

Celite. The light yellow solid was filtered off and washed three times with 10mL

aliquots of diethyl ether. The isolated yield of [Mn(h6-C6H5NMe2)(CO)3]BF4 was

0.18 g (0.52mmol, 94%).

Anal. Calcd (%): C, 38.08; H, 3.20; N, 4.04. Found (%): C, 39.04; H, 3.17; N, 4.30.

IR (CH2Cl2): 2066, 2000 cm�1. 1H NMR (acetone-d6): d 6.92 (t, H3,5), 6.09 (t,

H4), 5.87 (d, H2,6), 3.35 (s, Me).

Properties

N,N-Dimethylaniline(tricarbonyl)manganese(I) tetrafluoroborate is a yellow solid

(mp 168�C with decomp.). It dissolves readily in CH2Cl2 but is insoluble in ether,

aromatic, and aliphatic hydrocarbons.

References

1. D. A. Sweigart, J. A. Reingold, and S. U. Son, Manganese compounds containing CO ligands, in

Comprehensive Organometallic Chemistry, 3rd ed., R. H. Crabtree and D. M. P. Mingos, eds.,

Elsevier, Oxford, 2006, Vol. 5, Chapter 10, pp. 761–814.

2. (a) L. A. P. Kane-Maguire, E. D. Honig, and D. A. Sweigart, Chem. Rev. 84, 525 (1984).

(b) R. D. Pike, D. A. Sweigart, Coord. Chem. Rev. 187, 183 (1999). (c) D. A. Sweigart, T. J.

Alavosus, Y. K. Chung,W. A.Halpin, E. D. Honig, and J. C.Williams,Metal carbonyl cationswith

cyclic p-hydrocarbon ligands, in Organometallic Synthesis, R. B. Kingand J. J. Eisch, eds.,

Academic Press, New York, 1988, Vol. 4, p. 108.

3. J. D. Jackson, S. J. Villa, D. S. Bacon, R. D. Pike, and G. B. Carpenter, Organometallics 13, 3972

(1994).

4. (a) G. Winkhaus, L. Pratt, and G. Wilkinson, J. Chem. Soc. 3807 (1961). (b) P. L. Pauson and

J. A. Segal, J. Chem. Soc., Dalton Trans. 1677 (1975). (c) L. A. P. Kane-Maguire and D. A.

Sweigart, Inorg. Chem. 18, 700 (1979).

5. (a) R. Mews, Angew. Chem., Int. Ed. Engl., 14, 640 (1975). (b) F. L. Wimmer, M. R. Snow, and

Aust. J. Chem. 31, 267 (1978). (c) R. Uson, V. Riera, J. Gimano, M. Laguna, M. P. Gamasa,

J. Chem. Soc., Dalton Trans. 966 (1974). (d) F. A. Cotton, D. J. Darensbourg, and W. S.

Kolthammer, Inorg. Chem. 20, 1267 (1981).


6. (a) M. I. Rybinskaya, V. S. Kaganovich, and A. R. Kydinov, Izv. Akad. Nauk. SSR Ser. A Khim.

885 (1984). (b) A. J. Pearson and H. Shin, Tetrahedron 48, 7527 (1992).

7. (a) K. K. Basin, W. G. Balkeen, and P. L. Pauson, J. Organomet. Chem. 204, C25 (1981).

(b) Y.-A. Lee, Y. K. Chung, Y. Kim, and J. H. Jeong,Organometallics 9, 2851 (1990). (c) E. Jeong

and Y. K. Chung, J. Organomet. Chem., 434, 225 (1992). (d) S. S. Lee, J-S. Lee, and Y. K. Chung,

Organometallics 12, 4640 (1993). (e) S. C. Chaffee, J. C. Sutton, C. S. Babbitt, J. T. Maeyer,

K. A. Guy, and R. D. Pike, Organometallics 17, 5568 (1998).

8. S. P. Schmidt, J. Nitschke, and W. C. Trogler, Inorg. Synth. 26, 113 (1989).

9. W. J. Ryan, P. E. Peterson, Y. Cao, P. G. Willard, D. A. Sweigart, C. D. Baer, C. F. Thompson,

Y. K. Chung, and T.-M. Chung, Inorg. Chim. Acta 211, 1 (1993).

10. A. Auffrant, D. Prim, F. Rose-Munch, E. Rose, S. Schouteeten, and J. Vaissermann,

Organometallics 22, 1898 (2003).

11. (a) S. Sun, L. K. Yeung, D. A. Sweigart, T.-Y. Lee, Y. K. Chung, S. R. Switzer, and R. D. Pike,

Organometallics 14, 2613 (1995). (b) M. Oh, J. A. Reingold, G. B. Carpenter, and D. A. Sweigart,

Coord. Chem. Rev. 248, 561 (2004).

12. S. Sun, G. B. Carpenter, and D.A. Sweigart, J. Organomet. Chem. 512, 257 (1996).

13. C. A. Dullaghan, G. B. Carpenter, D. A. Sweigart, D. Kuck, C. Fusco, and R. Curci,

Organometallics 19, 2233 (2000).

14. (a) I. S. Lee, H. Seo, and Y. K. Chung, Organometallics 18 1091 (1999). (b) S. S. Lee, T.-Y. Lee,

J. E. Lee, I.-S. Lee, Y.K. Chung, and M.S. Lah, Organometallics 15, 3664 (1996).

15. (a) E. J. Watson, K. L. Virkaitis, H. Li, A. J. Nowak, J. S. D’Acchioli, K. Yu, G. B. Carpenter,

Y. K. Chung, and D. A. Sweigart,Chem. Commun. 457 (2001). (b) S. U. Son, K. H. Park, S. J. Lee,

Y. K. Chung, and D. A. Sweigart, Chem. Commun. 1290 (2001).

16. M. H. Quick and R. J. Angelici, Inorg. Synth. 19, 160 (1979).

29. BIS(1,5-CYCLOOCTADIENE)NICKEL(0)

Submitted by J. WOLFRAM WIELANDT� and DAVID RUCKERBAUER�

Checked by T. ZELL§ and U. RADIUS§

Bis(1,5-cyclooctadiene)nickel(0) is useful for the synthesis of a variety of novel

nickel complexes1–5 since the 1,5-cyclooctadiene ligands are easily displaced

by other stronger electron-donating ligands.6 The compound has been prepared

by reduction of nickel(II) salts with manganese powder7 or by sodium8 in the

presence of 1,5-cyclooctadiene. Moreover, triethylaluminum has become a com-

mon reducing agent, but butadiene is required as the protective atmosphere.9

A butadiene-free preparation procedure has been reported that uses diisobutyla-

luminum hydride (DIBAH) to reduce technical grade (90%) Ni3(acac)6.10 Here,

di(n-butyl)magnesium is used as an alternative,4 since it is cheap and much less

dangerous than triethylaluminum. Also, no butadiene atmosphere is required.

*Institute of Chemistry, Inorganic Department, Karl-Franzens-University, 8010 Graz, Austria.§Institut fur Anorganische Chemie der Julius-Maximilians-Universitat Wurzburg, Am Hubland,

D-97074 Wurzburg, Germany.


Di(n-butyl)magnesium can be purchased as a 1.0M solution in n-heptane.

Alternatively, the preparative method given below can be applied, which follows

the general synthetic pathway for dialkyl magnesium compounds outlined

by Kamienski.11 The preparation involves the treatment of an ethereal solution

of (n-butyl)magnesium bromide with n-butyl lithium solution in hexanes. Other

methods of preparation include treatment of (n-butyl)magnesium halide solutions

withMe(OCH2CH2)nOMe,12 1,4-dioxane,13 and THF,14 or reaction ofmagnesium

hydride with 1-butene under pressure in an autoclave.15

& Caution. Di(n-butyl)magnesium reacts violently with water, and in the

dry state it ignites spontaneously upon exposure to air. Nickel and its compounds

are regarded as carcinogens. It also can cause allergic reactions, asthma, and

chronic bronchitis. Uptake of large quantities of nickel may lead to lung

embolism, respiratory failure, and heart disorders. Therefore, all manipulations

should be performed with care in a well-ventilated hood.

Materials

1,5-Cyclooctadiene (Aldrich Chemicals) was distilled from sodium and stored

under argon. n-Butyl bromide and 1.6M n-butyl lithium solution were purchased

from Aldrich and used as received. Solvents used in the syntheses were dried with

appropriate drying agents16 and freshly distilled under inert gas before use. All

procedures are performed in an anhydrous, oxygen-free atmosphere using standard

techniques for bench-top inert atmosphere reactions.17,18

A. HEXAKIS(ACETYLACETONATO)TRINICKEL(II)

NiðNO3Þ2 �6H2Oþ2NaC5H7O2!NiðC5H8O2Þ2 �2H2Oþ4H2Oþ2NaNO3

3NiðC5H8O2Þ2 �2H2O!Ni3ðC5H8O2Þ6þ6H2O

Procedure

Under air, Ni(NO3)2�6H2O (29.8 g, 0.1mol) and 2,4-pentanedione (20.5 g,

0.205mol) are dissolved in water (40mL) and treated with a 0.2M aqueous

solution of NaOH (40mL). Immediately, a turquoise precipitate is formed. After

the addition is complete, the mixture is heated to reflux for 30min, cooled to

ambient temperature, and filtered. The filter cake iswashedwithwater (50mL) and

dried under air for 2 h; yield: 26.9 g (92%) of light turquoise bis(2,4-pentadionato)

nickel(II) dihydrate. In a 500-mL round-bottomed flask attached to a Dean–Stark

apparatus, a suspension of bis(2,4-pentadionato)nickel(II) dihydrate (26.9 g,

29. Bis(1,5-Cyclooctadiene)Nickel(0) 121

0.092mol) in toluene (150mL) is carefully heated to reflux under air. (Note: An oil

bath should be applied as heating source, not a heatingmantle. Themixture tends to

foam, and when heating is performed too rapidly, some of the solid material spills

over into the water collector.)9 The mixture is heated under reflux for 48 h until no

morewater is separated. A dark green slurry is formed, which is allowed to cool to

ambient temperature under inert gas. The insoluble parts are removed by filtration

with exclusion of air. The filter cake is extracted with dry toluene (20mL). All

filtrates are combined and are taken to dryness under vacuum. The oily residue is

rinsed with ether (30mL) in order to remove traces of grease. Solvent is decanted

from the green solid, which is dried under vacuum. Yield: 17.0 g (0.066mol).

B. DI(n-BUTYL)MAGNESIUM

n-C4H9BrþMg! n-C4H9MgBr

n-C4H9MgBrþ n-C4H9Li!ðn-C4H9Þ2MgþLiBr

Procedure

A500-mL three-necked round-bottomed flask is equippedwith a reflux condenser,

topped by a gas outlet, and two pressure-equalizing dropping funnels (one with

100mL volume and the other with 250mL volume). Before the second dropping

funnel is attached, dry magnesium turnings (6.1 g, 0.25mol) and a few crystals of

iodine are added to the flask. The apparatus is flushed with nitrogen for a few

minutes, and then the small dropping funnel is charged with n-butyl bromide

(34.26 g, 0.25mol) and the large one is filled with dry diethyl ether (100mL). The

magnesium turnings are heated without solvent with a heating gun until violet

fume has filled the whole apparatus. Then, approximately 5% of the volume of

n-butyl bromide is added to the hot magnesium turnings, followed by dropwise

addition of the solvent. As soon as the Grignard reaction starts, the bromide and

the solvent are added in a dropwise manner to keep the mixture refluxing gently.

(Note: The bromide should be added cautiously. An efficient reflux condenser is

recommended.)Upon complete addition, the dark graymixture is kept under reflux

for another 30min using a water bath.

Into the second reaction apparatus consisting of a 1-L three-necked round-

bottomed flask equipped with a reflux condenser, a gas inlet, and a pressure-

equalizing 250-mL addition funnel, the Grignard solution is transferred under

argon via cannula in order to separate it from unreacted magnesium. (Note: By

weighing the amount of unreacted Mg, the amount of n-butyl lithium solution

required can be accurately determined. Usually, the conversion is 90–95%.) The

dropping funnel is now charged with 1.6M n-butyl lithium solution in hexanes


(138mL, 0.220mol) and added dropwise under cooling with an ice bath. The

resulting gray suspension is heated at reflux for 30min, cooled to ambient

temperature, and filtered under nitrogen using a Schlenk frit attached to a 1-L

Schlenk flask. (Note: It is recommended that the inorganic salts be allowed to settle

prior to filtration, and the filtration process itself should be performed without

pressure to prevent LiBr from passing through the filter�.) The nearly colorless

clear filtrate is collected and used in the next step. (Note: An excess of reducing

agent does not affect the preparation described in step B.) To isolate the dibutyl

magnesium, the filtrate is evaporated to dryness under vacuum and the resulting

white solid is further dried at 10�2mbar at 60�C for 15 h to give 33.1 g (95%). This

solid contains small amounts of lithium bromide.

C. BIS(1,5-CYCLOOCTADIENE)NICKEL(0)

Ni3ðC5H7O2Þ6 þ 6 ðn-C4H9Þ2Mgþ 6C8H12 ! 3 ðC8H12Þ2Niþ 6 ðn-C4H9ÞMgðC5H7O2Þþ 3C8H18

Procedure

A 1-L three-necked round-bottomed flask is equipped with a 100-mL pressure-

equalizing dropping funnel and two gas outlets, one attached to a gas bubbler and

the other to an inert gas source. The flask is charged with Ni3(C5H7O2)6 (9.79 g,

0.038mol), 1,5-cyclooctadiene (15.22 g, 0.1408mol ofNi), andTHF (55mL). The

dropping funnel is charged with di(n-butyl)magnesium (0.075mol) obtained by

one of the following three methods:

(i) A commercial solution in n-heptane.

(ii) The diethyl ether/hexane filtrate from part B above.

(iii) A solution of di(n-butyl)magnesium (10.39 g, 0.075mol) in THF

(100mL). (Note: Solid di(n-butyl)magnesium dissolves slowly in THF

to give a slightly milky solution.)

The reaction flask is cooled to �100�C using an EtOH/N2 bath, and the MgBu2solution is slowly added dropwise, maintaining the reaction temperature below

�80�C. The addition requires approximately 2 h. The color of the reaction mixture

turns gradually from green to brownish-yellow over a period of several hours. Upon

completeaddition,thereactionmixtureisallowedtoreachambient temperatureandis

*The checkers removed insoluble material via filtration through a pad of dry Celite. The resulting

solutionwas used for the synthesis ofNi(cod)2 and transferred into the dropping funnel. The di(n-butyl)

magnesium solution in diethyl ether/hexane could not be stored > �40 ˚C.

29. Bis(1,5-Cyclooctadiene)Nickel(0) 123

stirredovernight.Thereactionmixture isevaporatedundervacuum,and thebrownish

residue is cautiously treated with MeOH (100mL)�. The resulting dark yellow

suspension is stirred for 10min and then allowed to settle, and the brown solution

is decanted or removed by cannula, leaving a fine yellow solid. (Note: Filtration

through Celite is possible in principle, but the frit is easily clogged.) The MeOH

washing step is repeated until the decanted solution is very pale. Finally, the yellow

material is extractedonceeachwithEtOH(50mL)andn-pentane(50mL)and is then

driedundervacuum(withprotectionfromlight)yielding9.1 g(0.033mol,87%)ofNi

(1,5-C8H12)2. This material is usually pure enough for further transformations�.

The product can be purified by recrystallization. Solid Ni(cod)2 (1–2 g) is

placed on top of a 1-cm layer of Celite on a Schlenk frit that is attached to a

250-mL Schlenk flask. Toluene (50mL) is added carefully, and the mixture is

carefully stirred with a plastic spatula while keeping the Celite settled. (Note:

Metal spatulas catalyze decomposition of the compound.) The dark yellowmixture

is carefully filtered to give a clear yellow filtrate. The procedure is repeated until

the extracts are almost colorless. The resulting filtrate is concentrated under

reduced pressure until incipient crystallization. The flask is filled with argon, and

the golden yellow solution is slowly treated with ether (50mL). (Note: If at this

stage some brown flakymaterial is formed, the mixture should be carefully filtered

once more.) The mixture is stored overnight at �30�C affording golden yellow

crystals that are isolated by removing the supernatant. A second crop can be

obtained by concentrating the mother liquor under vacuum to a few milliliters,

adding ether (20mL), and storing the mixture overnight at�30�C. The combined

recovery efficiency is usually 60–80%.

Anal. Calcd. for C16H24Ni: C, 69.9; H, 8.8%. Found: C, 69.6; H 8.9%. 1H NMR10

(C6D6): d 2.06 (s, 8H,CH2); 4.29 (s, bd, 4H,CH). The checkers found d 2.08 (s, 8H,CH2); 4.30 (s, 4H, CH).

Properties

The solid complex decomposes after several minutes in air; solutions decompose

in air more rapidly. It is moderately soluble in benzene and THF, but heating these

solutions above 60�C leads to decomposition. The solid decomposes at

135–140�C. It is nearly insoluble in diethyl ether and saturated hydrocarbons.

The complex is decomposed catalytically by halocarbons,19 and even upon storage

under inert gas for a prolonged time, it can decompose turning dark slowly.

*The checkers found that the methanolysis of the reaction mixture is a crucial step in the synthesis. The

MeOH used should be rigorously dried and the reaction mixture should be cooled using a iPrOH/CO2

cooling bath (�78 ˚C). It is important to proceed with the preparation since the reaction mixture

decomposes over MeOH after days. For storage, we advice to remove all volatiles in vaccuo.�The checkers obtained 80–85% yield of tan solid that was pure by 1H NMR spectroscopy.


References

1. A. J. Arduengo, III, S. F. Gamper, J. C. Calabrese, and F. Davidson, J. Am. Chem. Soc. 116, 4391

(1994).

2. R. M. Ceder, J. Granell, G. Muller, M. Font-Bard�ıa, and X. Solans, Organometallics 14, 5544

(1995).

3. S. Ogoshi, K. Tonomori, M. Oka, and H. Kurosawa, J. Am. Chem. Soc. 128, 7077 (2006).

4. M. J. Tenorio, M. C. Puerta, I. Salcedo, and P. Valerga, J. Chem. Soc., Dalton Trans. 653 (2001).

5. M. Stol, D. J.M. Snelders,M.D.Godbode,R.W.A.Havenith,D.Haddleton,G.Clarkson,M.Lutz,

A. L. Spek, G. P. M. van Klink, and G. van Koten, Organometallics 26, 3985 (2007).

6. S. D. Ittel, Inorg. Synth. 28, 98 (1990).

7. F. Guerini and G. Salerno, J. Organomet. Chem. 114, 339 (1976).

8. (a) H. M. Colquhoun, D. J. Thompson, and M. W. Twigg, New Pathways for Organic Synthesis,

Plenum Press, London, 1984, p. 389. (b) T. R. Belderra�ın, D. A. Knight, D. J. Irvine, M. Paneque,

M. L. Poveda, and E. Carmona, J. Chem. Soc., Dalton Trans. 1491 (1992).

9. R. A. Schunn, S. D. Ittel, and M. A. Cushing, Inorg. Synth. 28, 94 (1990).

10. D. J. Krysan and P. B. Mackenzie, J. Org. Chem. 55, 4229 (1990).

11. C. W. Kamienski and J. F. Eastham, J. Organomet. Chem. 8, 542 (1967).

12. Y. Saheki, K. Sasada, N. Satoh, N. Kawaichi, and K. Negoro, Chem. Lett. 2299 (1987).

13. W. Strohmeier and F. Seifert, Chem. Ber. 94, 2356 (1961).

14. K. L€uhder, D. Nehls, and K. Majeda, J. Prakt. Chem. 325, 1027 (1983).

15. B. Bogdanovi�c, P. Bons, S. Konstantinovi�c, M. Schwickardi, and U. Westeppe, Chem. Ber. 126,

1371 (1993).

16. W. L. F. Armarego and D. D. Perrin, Purification of Laboratory Chemicals, 4th ed., Butterworth/

Heinemann, Oxford, 1996.

17. D. F. Shriver and M. A. Drezdon, The Manipulation of Air-Sensitive Compounds, Wiley,

Chichester, 1986.

18. R. B. King, in Organometallic Syntheses, J. J. Eischand R. B. King, eds., Academic Press, Inc.,

New York, 1965, Vol. 1.

19. C. A. Tolman, D. W. Reutter, and W. C. Seidel, J. Organomet. Chem. 117, C30 (1976).

30. SODIUM (h5-CYCLOPENTADIENYL)TRIS(DIMETHYLPHOSPHITO-P)COBALTATE(III),

Na[(C5H5)Co{P(O)(OMe)2}3]

Submitted by WOLFGANG KL€AUI� and PETER C. KUNZ�

Checked by SABINE N. SEIDEL� and JOHN A. GLADYSZz

The chemistry of cobaltocene is dominated by its tendency to act as an

electron-rich radical that can undergo one-electron oxidation, ring addition,

*Lehrstuhl I: Bioanorganische Chemie und Katalyse, Heinrich-Heine-Universit€at D€usseldorf, 40225

D€usseldorf, Germany .�Lehrst€uhle f€ur Anorganische Chemie, 91058 Erlangen, Germany .zDepartment of Chemistry, Texas A&M University, College Station, TX .

30. Sodium (h5-Cyclopentadienyl)Tris(Dimethylphosphito-P)Cobaltate(III) 125

and ring substitution reactions. Secondary phosphites HP(O)(OR)2 react with

cobaltocene in a complex manner that includes both oxidation and ring substi-

tution to produce mixed-valence trinuclear cobalt complexes of the type [Co

((C5H5)Co{P(O)(OR)2}3)2]. This reaction is synthetically valuable since it gives

ready access to the anionic complexes [(C5H5)Co{P(O)(OR)2}3]�, a versatile

class of tripodal oxygen ligands. An important feature of these ligands is their

inertness and their high tendency to form complexes with main-group and

transition metals. In addition, they can stabilize a large variety of organometallic

fragments.1,2

A. [Co((C5H5)Co{P(O)(OMe)2}3)2], Co(LOMe)2

3CoCp2þ6HPðOÞðOMeÞ2!½CoððC5H5ÞCofPðOÞðOMeÞ2g3Þ2�þ4HCpþH2

Procedure

Freshly sublimed cobaltocene (25 g, 0.13mol) and 44mL (0.48mol) of dimethyl

phosphite, HP(O)(OMe)2, are added under a nitrogen atmosphere to a 250-mL

round-bottomed Schlenk flask equipped with a magnetic stirring bar. A reflux

condenser equippedwith a pressure relief valve is attached to the Schlenk flask and

the apparatus is purged with dry nitrogen. The reflux condenser need not to be

connected towater cooling; it is used as a splash guard. The oil bath temperature is

set to 100–120�C. After about 1 h, cyclopentadiene that is formed in the reaction

starts refluxing and orange crystals form. After several hours, the brown color of

cobaltocene disappears, but the solution is still dark. The heating is switched off

and the apparatus kept in the oil bath that slowly cools overnight. The air-stable

product forms as large orange crystals that are filtered off, washedwith ethanol and

pentane, and dried in vacuo. The yield is 40 g (42mmol, 94%).

Properties

[Co((C5H5)Co{P(O)(OMe)2}3)2] is thermally stable up to 300�C, paramagnetic,

and soluble in chlorinated solvents and in strong acids.3 The infrared spectrum

(KBr wafer) has medium to strong absorptions at 2980, 2840, 1425, 1175, 1125,

1035, 1005, 835, and 585 cm�1.

B. Na[(C5H5)Co{P(O)(OMe)2}3], NaLOMe

2 ½CoððC5H5ÞCofPðOÞðOMeÞ2g 3Þ2� þ 12NaCNþ 0:5O2 þH2O!4Na½ðC5H5ÞCofPðOÞðOMeÞ2g3� þ 2Na3½CoðCNÞ6� þ 2NaOH


Procedure4

Co(LOMe)2 (40 g, 42mmol) is suspended in 350mL of methanol in a 1-L three-

necked round-bottomed flask equipped with a thermometer and a gas inlet with a

porous frit. The suspension is cooled to �10 to �5�C in an acetone/ice bath.

A vigorous stream of pressurized air is bubbled through the suspension. Sodium

cyanide (14 g, 0.29mol) is then added slowly to the suspension in small portions

over the course of 1 h. The reaction mixture is stirred for one more hour, and then

the solvent is removed using a rotary evaporator and the residue dried in vacuo.

The resulting yellow solid is transferred to a Soxhlet apparatus and the sodium

salt of the tripodal oxygen ligand, NaLOMe, is separated from the sodium salts

Na3[Co(CN)6] and NaCN by extraction with dichloromethane. The extraction

requires several days. Rotary evaporation of the extract followed by drying

in vacuo leaves NaLOMe as bright yellow powder. The yield is 36–38 g

(76–80mmol, 91–96%). The product is pure enough for most purposes. If

necessary, it can be dissolved in twice distilled water, and the solution filtered

through amembrane followed by evaporation at room temperature. Single crystals

of a coordination polymer of NaLOMe have been obtained by slow diffusion of

pentane into a solution of NaLOMe in dry dichloromethane.5

31P{1H} NMR (CDCl3): d 111 (s). 1H NMR (CDCl3): 3.6 (virt. q, 18H,3JHCOP ¼ 11 Hz, OCH3), 5.1 (q, 5H,

3JHCCoP ¼ 0:5 Hz, C5H5). IR (KBr): medium

to strong absorptions at 2835, 1430, 1170, 1080, 835, 750, 580 cm�1.

Properties

The tripodal oxygen ligandNaLOMe is very soluble inwater andmethanol, but only

very slightly soluble in acetone, diethyl ether, and pentane. Freshly precipitated

NaLOMe is soluble in CH2Cl2, but recrystallized solid is not.

The sodium salt of the corresponding ligand [LOEt]�, [(C5H5)Co{P(O)

(OEt)2}3]�, prepared analogously from cobaltocene and HP(O)(OEt)2, crystal-

30. Sodium (h5-Cyclopentadienyl)Tris(Dimethylphosphito-P)Cobaltate(III) 127

lizes from water as 3NaLOEt�4H2O.6 It is much more soluble in organic solvents,

even in pentane, as well as in water. For sterically demanding ligands such as

[LOPh]�, other synthetic routes are available.7 Tripodal oxygen ligands of the type

[(C5R05)M{P(O)(OMe)2}3]

� with M ¼ Rh or Ir and R0 ¼ H, CH3 are accessible

via Michaelis–Arbuzov reactions of Rh(III) and Ir(III) complexes with

trimethylphosphite.8,9

References

1. W. Kl€aui, Angew. Chem. 102, 661–670 (1990); Angew. Chem., Int. Ed. Engl. 29, 627–637 (1990).

2. W.-H. Leung, Q.-F. Zhang, and X.-Y. Yi, Coord. Chem. Rev. 251, 2266–2279 (2007).

3. W. Kl€aui, H. Neukomm, H. Werner, and G. Huttner, Chem. Ber. 110, 2283–2289 (1977).

4. W. Kl€aui, B. Lenders, B. Hessner, and K. Evertz, Organometallics 7, 1357–1363 (1988).

5. W. Kl€aui, D. Matt, F. Balegroune, and D. Grandjean, Acta Crystallogr. C 47, 1614–1617 (1991).

6. W. Kl€aui, A. M€uller, W. Eberspach, R. Boese, and I. Goldberg, J. Am. Chem. Soc. 109, 164–169

(1987).

7. W. Kl€aui, H.-O. Asbahr, G. Schramm, and U. Englert, Chem. Ber. 130, 1223–1229 (1997).

8. W. Kl€aui, H. Otto, W. Eberspach, and E. Buchholz, Chem. Ber. 115, 1922–1933 (1982)

9. M. Scotti, M. Valderrama, P. Campos, and W. Kl€aui, Inorg. Chim. Acta 207, 141–145 (1993).


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