18 electron rule: ean rule (effective atomic number)
DESCRIPTION
18 electron rule: EAN rule (Effective Atomic Number). In 1927, developed by Sidgwick. d electrons of metal + electrons of ligand = 18 electrons. 4 5 6 7 8 9 10 11 12 d 3 d 4 d 5 d 6 d 7 d 8 d 9 d 10 Sc Ti V Cr Mn Fe Co Ni Cu Zn - PowerPoint PPT PresentationTRANSCRIPT
18 electron rule: EAN rule (Effective Atomic Number)
In 1927, developed by Sidgwick
3 4 5 6 7 8 9 10 11 12
d3 d4 d5 d6 d7 d8 d9 d10 Sc Ti V Cr Mn Fe Co Ni Cu ZnY Zr Nb Mo Tc Ru Rh Pd Ag Cd Ta W Re Os Ir Pt Au Hg
d electrons of metal + electrons of ligand = 18 electrons
Ni: 1s22s22p63d84s2 : it is better to promote 4s electron to 3d, therefore Ni(0) is d10.Cu(I), Ag(I), and Au(I) is d10, Zn2+, Cd2+, and Hg2+ is d10
Ti(IV) serves as a good index for memorizing the d electronsBecause it is a d0 metal ion.TiCl4 is colorless, diamagnetic liquidTiCl3 is violet color
octahedraltetrahedral
Trigonal bipyramidSquare planar
Electrons
Ligand
1 수소라디칼 (H radical), 알킬 라디칼 (alkyl radical), 아릴 라디칼(aryl radical) , 할로겐 라디칼 (halogen radical), NO ( 굽은 형태 )
2 CO, CS, RCN, R3N, R3P, R3As, RCN, R2S, 수 소 음 이 온 (H-), 알킬음이온 (R-), 알켄 (alkene), η3- 알릴 양이온 (η3-allyl+), 알킨(alkyne), 니트로실 양이온 (NO+), 할로겐 음이온 (X-)
3 η3- 알릴 라디칼 (η3-allyl), NO ( 직선형 )4 η3- 알 릴 음 이 온 (η3-allyl-), η4-C4R4(η4-cyclobutadiene), η4-
비공액디엔 (nonconjugate diene), η4- 공액디엔 (conjugate diene)
5 η5-C5R5 라디칼 (η5-cyclopentadienyl radical)
6 η5-C5R5 음 이 온 (η5-cyclopentadienyl anion), η6-C6R6, η7-C7R7 양이온 (cycloheptatrienyl cation)
7 η7-C7R7 라디칼 (cycloheptatrienyl radical)
8 η8-C8R8 (cyclooctatetraene)
CH3-Mn(CO)5
homolytic cleavage
hetreolyticcleavage
CH3 (radical) + Mn(CO)5
CH3- (anion) + Mn(CO)5
+
homolytic cleavageCH3Mn(CO)5
Mn0(3d7) 7 ÀüÀÚ
CH3 (radical) 1 ÀüÀÚ
5 CO 10 ÀüÀÚ
18 ÀüÀÚ
heterolytic cleavageCH3Mn(CO)5
Mn+(3d6) 6 ÀüÀÚ
CH3 - (anion) 2 ÀüÀÚ
5 CO 10 ÀüÀÚ
18 ÀüÀÚ
.
.
Ni(CO)4, Fe(CO)5, Cr(CO)6, Ni(CO)4,
For Mn, Mn(CO)5: 17 electrons
Mn(CO)6: 19 electrons
Mn(CO)5 (CO)5Mn-Mn(CO)5
HMn(CO)5, CH3Mn(CO)5, ClMn(CO)5
CH3Mn(CO)5
CH3- + Mn(CO)5
+
(CO)4Re
Cl:....
:Cl
Re(CO)4
....
Re (3d7) 7 electrrons
4 CO 8 electrons
Cl radical 1 electrons
Cl (nonbonding) 2 electrons
18 electrons
18 Electron Rule: strong field ligand such as CO, Hydride, Cycanide anion.
Not good for Aqua complex: Weak Field Ligand such as H2O is not matched with 18 electron rule.
Late transition metal is better than early transition metals.
Exceptions
Early trantion metals(η5-C5H5)2ZrCl2: 5ex2+4e+2e=16e, (CH3)3TaCl2 는 1ex3+5e+2e=10e(CH3)6W 는 1ex6+6e=12e
For early transition metals, there is not enough room to attach many ligands to satisfy 18 electron rule.Coordination number: number of ligand to bind to metal. Coordination number cannot be larger than the maximun oxidation number or the group number of element.For Late transition Metals(PPh3)3Pt: 2ex3+10e=16e (η5-C5H5)2Ni:5ex2+10e=20e
d8complex: 16 electrons
Pt(II), Pd(II), Cu(III), Ir(I), Rh(I): square planar For example, Cl(PPh3)3Rh(I) (Wilkinson’s complex), Cl(PPh3)2(CO)Ir(I) (Vaska’ complex), (PPh3)2(CCPh)2Pt(II) even though they contains strong field ligand
IrPh3P Cl
OC PPh3
+ Cl2Ir
Ph3P Cl
OC PPh3
Cl
Cl
Ir+1 (5d8) 8 e
2 PPh3 4 e
1 CO 2 e
Cl-(anion) 2 e
16 e
Ir+3 (5d6) 6 e
2 PPh3 4 e
1 CO 2 e
3 Cl-(anion) 6 e
18 e
(5-C5H5)2FeH+ H-
[(5-C5H5)2FeH]-[(5-C5H5)2FeH]+
18 e 20e18 e
2 Fe(CO)5-CO
Fe2(CO)9 -COFe3(CO)12
Fe(CO)5light
V(CO)6 + Na [V(CO)6]- + Na+
Fe
FeFe
COCO
CO
OC
COOC
CO
CO
OC
OCO
O M
MM
COCO
CO
CO
COOC
CO
CO
OC
OC
CO
CO
Fe3(CO)12 M3(CO)12
M = Ru, Os
Co Co
CO
OC CO
OC
OC CO
CO
CO
Co Co CO
COOCOC
CCOC
O O
Co2(CO)8ÀÇ µÎ °¡ Áö ÇüÅÂ
1.3 Mechanism in Organometallic Chemistry
1.oxidative addition ( 산화성부가반응 ) and reductive elimination ( 환원성 제거반응 ) 2. insertion ( 삽입반응 ) and deinsertion ( 이탈반응 ) 3. Oxidative coupling ( 산화성결합반응 )and Reductive Cleavage ( 환원성결합분열 )
1. oxidative addition ( 산화성부가반응 ) and reductive elimination ( 환원성 제거반응 )
two electron oxidative addtion ( 이전자 산화성부가반응 ) and one electron oxidative addition ( 일전자 산화성부가반응 )
X
Y+ Mn
X Mn+2 Y
X Mn+2 + Y-
two electronoxidative addition
(A)
(B)
A; 16 electron complexesB: 18 electron complexes
IrOC L
L X MeIIr
OC L
L XMe
I
H2IrOC L
L HH
X
Ir(I), d8Ir(III), d6 Ir(III), d6
(CO)4Fe2- RX[R-Fe(CO)4]-
+ X-
Fe2-, (d10) Fe0, (d8)
H2N.R.
Na2Fe(CO)4
18 electron complex[RFe(CO)4]+X-
18 electron complex
H2Fe(CO)2-4
20 electron complex
IrPh3P Cl
OC PPh3
IrPh3P Cl
OC PPh3
Me
I
IrPh3P Cl
OC PPh3
ArSO2
Cl
IrPh3P Cl
OC PPh3
HgCl
Cl
IrPh3P PPh3
OC OO
Cl
IrPh3P PPh3
OC CC
Cl
IrPh3P H
OC PPh3
R3Si
Cl
IrPh3P H
OC PPh3
H
Cl
CO2Me
MeO2C
MeI
HgCl2
ArSO2Cl
O O
H2
R3SiH
MeO2C CO2Me
Oxidative Addition of Vaska's complex
X
Y+ 2 Mn ÀÏÀüÀÚ »êÈ ¼ººÎ °¡ ¹ÝÀÀ
X Mn+1 + Y Mn+1
2 Co(CN)53- H2 2 HCo(CN)5
3-RCo(CN)53- + XCo(CN)5
3- R-X
Co+3 Co+3 Co+2 Co+3
Rh(II), Co(II) d7 complex
PRuP
P
P
Me2Me2
Me2Me2
+Ru
H(dmpe)
Kinetic FactorThermodynamic Factor
1965, Chatt and Davidson
In 1982, Bergman, Graham, Jones
IrMe3P H
H
hIr
Me3P
RHIr
Me3P HR
-H2
M + M
Me
Me
IrL L
+
IrL Me
L
Me +
Endo methyl migration: aromatic stablization energy
N
C OR
+ N
C ORh
R
ClRh Cl
nn
R= -CH2Ph, CH3, C2H5
Py N
C ORhR
Cl
PyPy
Py=pyridine
Reductive Elimination: spontaneous
MA
BM + A
B
M A + M' B M M' A B+
To do reductive elimination, two ligands should be placed at cis-position
Concerted Mechanism
P
Ni
PMe Me
Me Me
Me
PhPh Me
Me
Ni
Ph
L LL
No ReactionDMPE
-2L
Ph2P PPh2PdMe
MeNo ReactionCD3I
Ph2P PPh2PdMe
Me
CD3 I-
+
Ph2P PPh2PdMe
I
+
CH3-CD3
Transphos Ligand: Pd(II) is dsp2 (square planar):no reductive eliminationAddition of CH3I allows to make cis-dimethyl to undergo reductive elimination.
Me
Pt
Me
Et PPh3
-PPh3Me
Pt
Me
Et Pt
Me
Et Me
Et Me
2. Elimination of one of ligand to make T-shape to Y shape.
3. Reduce the electron density of central metal
O-C6H5
(bipy)Ni
C
O
OOO
RNi(bipy) O
O
O2
+R C
O
OC6H5
Ligand off from metal by heat or light, oxidize the metal,addition of strong pi-acceptor ligand such as CO, maleic anhydride, quinone, tetracyanoethylene
1. Insertion ( 삽입반응 ) and Deinsertion (이탈반응 )
M-R + X M-X-R
Insertion
deinsertion
R=alkyl, aryl, hydride; X = CO, C=C, C=N, etc
LnMR
COLnM
R
CO
LnM C
O
R
Migratory Insertion: cis position and concerted mechanism
Order: 3-allyl ≥ Et 〉 Me 〉 PhCH2 〉 vinyl ≥aryl, ROCH2 〉 HOCH2
Hard to migrate to CO: Hydride(H-), acyl (CH3CO), CF3 ,
Heteroatome: RO-, R2N
Decarbonylation
RhClL3
-LRhClL2 PhCH2C Rh
L
L Cl
Cl
O
L
Rh
LClPhCH2
ClOC
RhCl(CO)L2 + PhCH2Cl
L = PPh3 PhCHO
R-C Rh
Cl
H L
L
O
Cl
Rh
HLR
LOC RH+
RhCl(CO)L2
PhCH2COCl
PhCH2COCl
PhCHO
RhClL3 RhCl(CO)L2 + PhCH2Cl
RH RhCl(CO)L2+RhClL3
Hydride Insertion: cis-addition, 4-centered transition stateFor example: hydroboration, hydrosilylation, hydroformylation
ML H
-L
M H
-L
HM
Reverse Reaction: -Hydride Elimination The reason why it is hard to make a long chain alkylmetal complex
Alkyl Migration into olefin: olefin polymerization
CoCD3
CD3
C2H4 CoCD3H2C
H2C CD3
CoCD3
HD3C
Co
PMe3
+
CH2=CH-CD3C2H4
PMe3CD3H
Order of Migration of sigma liand-metal complex to Olefin: H >> R, vinyl, aryl> RCO>>RO, R2N
Heteroatom is hard to migrate because of strong bond of heteroatom bearing lone pair to metal
M O R M O R M O R....
M NR
RM N
R
R
..
M
R(H)
M
(H) R(cis form)
Alkyne undergoes migratory insertion, but further successive reaction makepolymer compounds, which make complication.
Other Insertion, deinsertion substrate;isocyanide (:C≡NR), carbene(:CR2), SO2 , etc
M M
:NuNu
Nucleophilic Addition Reaction ( 친핵부가반응 ) reverse sterechemistry to migratory insertion High valent metal species: electron deficient metal
FeOC
OC
+ + Nu- FeOC
OCNu
Nu- = MeO-, t-BuS-, PPh3, R2NH, -CH2NO2, -CH(CO2Me)2, LiCuMe2, etc.
FeOC
L
+
+ Nu- FeOC
LNu
Nu = PhS-, CN-, -CH(CO2Et)2, etc. L = PPh3, P(OPh)3
Trans-Addition Product
> > > > >> > > >
Order of Reactivity
1.4.3 Oxidative coupling ( 산화성결합반응 ) Reductive Cleavage ( 환원성결합분열 )
Moxidative coupling
reductive cleavage
M
M: +2 Increase
Fe(CO)5
F2C CF2
CF2
CF2
CF2
F2C
M
Electron withdrawing or strained molecules
FeL4 L3Fe
For alkyne, electron-withdrawing is no necessary
Mreductive elimination
oxidatve addition
M
Mreductive elimination
oxidatve addition
M