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