Transcript 18 electron rule: EAN rule (Effective Atomic Number)

18 electron rule: EAN rule (Effective Atomic Number)
In 1927, developed by Sidgwick
d electrons of metal + electrons of ligand = 18 electrons
3
4
5
6
7
8
9
d3
Sc
Y
d4
Ti
Zr
d5
V
Nb
Ta
d6
Cr
Mo
W
d7
Mn
Tc
Re
d8
Fe
Ru
Os
d9
Co
Rh
Ir
10
11 12
d10
Ni
Cu
Pd Ag
Pt
Au
Zn
Cd
Hg
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 electrons
Because it is a d0 metal ion.
TiCl4 is colorless, diamagnetic liquid
TiCl3 is violet color
octahedral
Trigonal bipyramid
tetrahedral
Square 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, 수소음이온(H-), 알
킬음이온(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-알릴 음이온(η3-allyl-), η4-C4R4(η4-cyclobutadiene), η4비 공 액 디 엔 (nonconjugate diene), η4- 공 액 디 엔 (conjugate
diene)
5
η5-C5R5 라디칼(η5-cyclopentadienyl radical)
6
η5-C5R5 음 이 온 (η5-cyclopentadienyl anion), η6-C6R6, η7C7R7 양이온(cycloheptatrienyl cation)
7
η7-C7R7 라디칼(cycloheptatrienyl radical)
8
η8-C8R8 (cyclooctatetraene)
CH3-Mn(CO)5
homolytic
cleavage
hetreolytic
cleavage
homolytic cleavage
CH3Mn(CO)5
Mn0(3d7)
.
7 ÀüÀÚ
.
CH3 (radical) + Mn(CO)5
CH3- (anion) + Mn(CO)5+
heterolytic cleavage
CH3Mn(CO)5
Mn+(3d6)
6 ÀüÀÚ
CH3 (radical) 1 ÀüÀÚ
CH3 - (anion) 2 ÀüÀÚ
5 CO
5 CO
10 ÀüÀÚ
18 ÀüÀÚ
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+
..
:Cl
..
(CO) 4Re
7
..
Cl:
..
Re (3d )
4 CO
Cl radical
Cl (nonbonding)
Re(CO) 4
7 electrrons
8 electrons
1 electrons
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)3TaCl2는 1ex3+5e+2e=10e
(CH3)6W는 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
OC
Ir
Ph3P
Cl
PPh3
OC
+
Cl
Ir
Cl2
Ph3P
Cl
PPh3
Cl
Ir+1 (5d8)
8e
Ir+3 (5d6)
6e
2 PPh3
4e
2 PPh3
4e
1
2e
1
2e
CO
Cl-(anion)
2e
16 e
CO
3 Cl-(anion)
6e
18 e
5
[( -C5H5)2FeH]
+
H+
18 e
( -C5H5)2Fe
H-
[(5-C5H5)2FeH]20e
18 e
light
-CO
2 Fe(CO)5
V(CO)6
5
+
Na
Fe2(CO)9
Fe(CO)5
-CO
[V(CO)6]-
Fe3(CO)12
+
Na+
CO
OC
OC Fe
CO
CO CO
O
Fe
CO
CO
OC
OC M
OC
CO CO
M
CO
CO
Fe
M
O
OC CO
CO
OC
CO
CO
M3(CO)12
Fe3(CO)12
M = Ru, Os
OC
CO
OC Co
CO
Co
CO OC
CO
CO
OC
O
O
C
C
Co
Co
OC
OC
Co2(CO)8ÀǵΠ°¡ ÁöÇüÅÂ
CO
CO
CO
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
two electron
oxidative addition
A; 16 electron complexes
B: 18 electron complexes
X
Mn+2 Y
X Mn+2
+ Y-
(A)
(B)
H
L
Me
H
OC
L
H2
Ir
Ir
L
OC
X
MeI
L
L
X
Ir
OC
L
I
Ir(III), d6
N.R.
X
Ir(I), d8
H2
H2Fe(CO)2-4
20 electron complex
2-
(CO)4Fe
2-
10
Fe , (d )
Na2Fe(CO)4
18 electron complex
RX
Ir(III), d6
[R-Fe(CO)4]- +
Fe0, (d8)
[RFe(CO)4]+X18 electron complex
X-
Me
OC
H
OC
Ir
Ph3P
Cl
Ir
PPh3
Ph3P
I
PPh3
HgCl
OC
PPh3
Ir
Ph3P
Cl
Cl
Cl
H
MeI
H2
HgCl2
R3Si
OC
PPh3
Ir
Ph3P
H
Cl
MeO2C
R3SiH
OC
Ir
Ph3P
CO 2Me
MeO2C
C
OC
C CO 2Me
Ir
Ph3P
PPh3
Cl
PPh3
ArSO2
OC
PPh3
Ir
Ph3P
Cl
Cl
ArSO2Cl
Cl
O O
O
OC
O
Ir
Ph3P
Oxidative Addition of Vaska's complex
Cl
PPh3
X
+ 2 Mn
ÀÏÀüÀÚ»êÈ-¼ººÎ °¡ ¹ÝÀÀ
Y
X Mn+1
+
Y Mn+1
Rh(II), Co(II) d7 complex
RCo(CN)53- + XCo(CN)53Co
+3
Co+3
R-X
2 Co(CN)53Co+2
H2
2 HCo(CN)53Co+3
1965, Chatt and Davidson
Me2 Me2
P P
Ru
P P
Me2 Me2
H
+
(dmpe) Ru
Kinetic Factor
Thermodynamic Factor
In 1982, Bergman, Graham, Jones
RH
h
Ir
Me3P
H
H
M +
-H2
Ir
Ir
Me3P
Me3P
M
R
H
Me
+
Me +
Me
Ir
Ir
L
L
L
L
Me
Endo methyl migration: aromatic stablization energy
+
N
Rh
C O
R
R= -CH2Ph, CH3, C2H5
Cl
Cl
n
N
Rh
R
Py
C O
n
Cl
Py
Py=pyridine
N
Rh
Py
C O
R
Reductive Elimination: spontaneous
A
M
M
+
B
M A + M' B
M M'
A
B
+
A B
To do reductive elimination, two ligands should be placed
at cis-position
Concerted Mechanism
Me
No Reaction
L
L Ni
L
Ph
DMPE
-2L
Me Me
P
Me
Ni
Ph
P
Me Me
Ph Me
Transphos Ligand: Pd(II) is dsp2 (square planar):
no reductive elimination
Addition of CH3I allows to make cis-dimethyl to undergo
reductive elimination.
CH3-CD3
+
No Reaction
CD3I
Me
Ph2P Pd
Me
Me
PPh2
+
Ph2P Pd
Me CD3
I
PPh2
I-
Ph2P Pd
Me
PPh2
2. Elimination of one of ligand to make T-shape to Y shape.
Me
Et Pt
PPh3
Me
-PPh3
Et
Me
Et
Me
Pt
Pt
Me
Me
Et Me
3. Reduce the electron density of central metal
Ligand off from metal by heat or light, oxidize the metal,
addition of strong pi-acceptor ligand such as CO, maleic
anhydride, quinone, tetracyanoethylene
O-C 6H5
(bipy)Ni
C R
O
O
O
O
O
Ni(bipy)
+
O
2
O
R C OC6H5
O
1. Insertion (삽입반응) and Deinsertion (이탈
반응)
Insertion
M-R + X
M-X-R
deinsertion
R=alkyl, aryl, hydride; X = CO, C=C, C=N, etc
Migratory Insertion: cis position and concerted
mechanism
R
LnM
CO
R
LnM
CO
LnM C R
O
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
PhCH2COCl
RhClL3
PhCHO
RhClL3
L = PPh3
-L
RhClL2
RH
PhCH2COCl
PhCHO
Cl L
R-C Rh
O H L
RhCl(CO)L2 + PhCH2Cl
Cl
OC
L
Rh
R
L
H
L Cl
PhCH2C Rh
O L Cl
RH
+
RhCl(CO)L2
+
RhCl(CO)L2
L
OC
Cl
Rh
PhCH2
Cl
L
RhCl(CO)L2 + PhCH2Cl
Hydride Insertion: cis-addition,
4-centered transition state
For example: hydroboration, hydrosilylation,
hydroformylation
-L
L M H
-L
M H
M
H
Reverse Reaction: b-Hydride Elimination
The reason why it is hard to make a long chain
alkylmetal complex
Alkyl Migration into olefin: olefin polymerization
Co
C2H4
H2C
CD 3
CD 3
CH2=CH-CD3
Co
PMe3
+
CD3H
Co
CD 3
H2C CD
3
C2H4
PMe3
Co
H
D3C
CD 3
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
R
..
M N
R
M O R
R
M N
R
M O
R
Alkyne undergoes migratory insertion,
but further successive reaction make
polymer compounds, which make complication.
M
R
(H)
M
(cis form)
(H) R
Other Insertion, deinsertion substrate;
isocyanide (:C≡NR), carbene(:CR2), SO2 , etc
Nucleophilic Addition Reaction (친핵부가반응)
reverse sterechemistry to migratory insertion
High valent metal species: electron deficient metal
:Nu
Nu
M
M
OC Fe+
+
Nu-
OC Fe
Nu
OC
OC
Nu- = MeO-, t-BuS-, PPh3, R2NH, -CH2NO2, -CH(CO2Me)2, LiCuMe2, etc.
Trans-Addition Product
+
OC Fe
+
Nu-
L
Nu = PhS-, CN-, -CH(CO2Et)2, etc.
OC Fe
Nu
L
L = PPh3, P(OPh)3
Order of Reactivity
>
>
>
>
>>
>
>
>
1.4.3 Oxidative coupling (산화성결합반응)
Reductive Cleavage (환원성결합분열)
M: +2 Increase
oxidative coupling
M
M
reductive cleavage
Electron withdrawing or strained molecules
Fe(CO) 5
F2C CF 2
F2
C
M
CF 2
C CF 2
F2
For alkyne, electron-withdrawing is no necessary
FeL4
L3Fe
M
M
reductive elimination
M
oxidatve addition
reductive elimination
M
oxidatve addition