Download Organometallics Study Meeting

Organometallics Study Meeting
04/21/2011
H.Mitsunuma
1. Crystal field theory (CFT) and ligand field theory (LFT)
CFT: interaction between positively charged metal cation and negative charge on the non-bonding electrons of the ligand
LFT: molecular orbital theory (back donation...etc)
Octahedral (figure 9-1a)
d-electrons closer to the ligands will have a higher energy than those further away which results in the d-orbitals splitting in
energy.
ligand field splitting parameter (
1) high oxidation state
2) 3d<4d<5d
3) spectrochemical series
0):
energy between eg orbital and t2g orbital
I-< Br-<
S2-< SCN-< Cl-< N3-, F-< (H2N)2CO, OH-< ox, O2-< H2O< NCS- <C5H5N, NH3< H2NCH2CH2NH2< bpy, phen< NO2< CH3-, C6H5-< CN- <CO
cf) pairing energy: energy cost of placing an electron into an already singly occupied orbital
Low spin:
If 0 is large, then the lower energy orbitals(t2g) are completely filled before population of the higher orbitals(eg)
High spin:
If 0 is small enough then it is easier to put electrons into the higher energy orbitals than it is to put two into the same low-energy
orbital, because of the repulsion resulting from matching two electrons in the same orbital
ex) (t2g)3(eg)n (n= 1,2)
Tetrahedral (figure 9-1b), Square planar (figure 9-1c)
LFT
(figure 9-3, 9-4)
Cl-, Br-: lower 0 (figure 9-4 a)
CO: higher 0 (figure 9-4 b)
2. Ligand
metal complex
alkyl
hydride
halogen
alkoxide
MR
MH
M X
M OR
O
M
hapticity formal chargeelectron donation metal complex
R
M
1
1
-1
-1
2
2
1
1
-1
-1
2
2
acyl
1
-1
2
1
-alkenyl
1
-1
2
1
-allyl
1
-1
2
acetylide
1
-1
2
carbene
1
0
2
carbene
1
-2
4
M
M
R
R
M
R
R
M
R
M
carbyne
1
-3
6
M CO
carbonyl
1
0
2
M
2
2
0
2
M
2
-alkyne
2
0
2
3
-allyl
3
-1
4
-diene
4
0
4
5
-1
6
M
M
M
-alkene
4
5
-cyclo
pentadienyl
M
H
M M
X
M M
R
O
M M
O
C
M M
R2
C
M M
O
C
MMM
R
C
M
MM
hapticity formal chargeelectron donation
6
-arene
6
0
6
-hydride
1
-1
2
-halogen
1
-1
4
-alkoxide
1
-1
4
-carbonyl
1
0
2
-alkylidene 1
-2
4
3
0
2
3
-3
6
-carbonyl 1
-alkylidine 1
1
3. d-electron
(OC)4Co Co(CO)4
Mo(IV): d2 = 2e
2(C5H5)-: 2 x 6e = 12e
2H-: 2 x 2e = 4e
Mo H
H
Co(0), d9, 18e
Co(0): d9 = 9e
4(CO): 4 x 2e = 8e
Co-Co: 1 x 2e = 2e
Mo(IV), d2, 18e
M(valency), [d-electron of M(0)] - [formal charge], [d-electron of metal] + [electron of ligand]
Early transition metal: smaller d-electron number (group 4, 5...)
Late transition metal: larger d-electron number (group 9, 10...)
4. 18-electron rule
Valence shells of transition metal consists of nine valence orbitals (s, p, d), which collectively can accommodate 18 electrons
(same electron configuration as noble gas) either as nonbinding electron pairs or as bonding electron pairs.
18-electron complex: coordinatively saturated complex
non-18-electron complex: coordinatively unsaturated complex
Violations to the 18-electron rule
Octahedral
[Co(H2O)2+6]2+ (19e)
[Ni(en)3] (20e)
V(CO)6 (17e)
W(CH3)6 (12e)
late transition metal: small 0
occupation of eg
Square planar
[(C6H5)3P]2PdX2 (16e)
[(C6H5)3P]2Ir(CO)X (16e)
early transition metal
instability of dx2-y2
stable alkyl complexes
Zr(CH2C6H5)4
W(CH3)6
W(VI), d0, 12e Zr(IV), d4, 8e
5. -bonding ligand
5.1 alkyl complex
Ti[CH2C(CH
3)3]4
Ti(IV), d0, 8e
M-C bond: 130~300 kJmol-1
-hydride elimination
Cr
Fe
4
Cr(IV), d2, 10e
4
Fe(IV), d4, 12e
L2Pt
Pt(II), d8, 16e
synthesis of alkyl complexes
1) Metathetical exchange using a carbon nucleophile
PR3
Cl Pt Cl
PR3
+
PR3
n-Bu Pt n-Bu
PR3
2 n-BuLi
Pt(II), d8, 16e
Pt(II), d8, 16e
2) Metal centered nucleophile
-
OC Fe
+
OC
Na+
3) Oxidative addition
Ph3P
CO
Ir
Br
PPh3
+ MeCl
Ir(I), d8, 16e
Me
Ph3P
CO
Ir
Br
PPh3
Cl
Ir(III), d8, 18e
4) Insertion
-
Br
OC Fe
OC
Fe(0), d8, 18e
Fe(II), d6, 18e
PR3
Cl Pt H
PR3
+
CH2=CH2
Pt(II), d8, 16e
PR3
Cl Pt Et
PR3
Pt(II), d8, 16e
5.2 hydride complex
M-H bond: 240~350 kJmol-1
synthesis of hydride complexes
1) Metal halide + reductant
3) Oxidative addition
RuCl2(PPh3)3 + NaBH4 + PPh3
Ru(II), d6, 16e
2) Protonation
Cp2WH2 + H+
W(IV), d2, 18e
[Co(CO4)]- + H+
Co(-I), d10, 18e
[Cp2WH3]+
W(VI), d0, 18e
HCo(CO4)
Co(I), d8, 18e
RuH2(PPh3)4
Ru(II), d6, 18e
IrCl(CO)(PPh3)2 + H2
8
Ir(I), d , 16e
RhCl(PPh3)3 + H2
Rh(I), d8, 16e
IrH2Cl(CO)(PPh3)2
Ir(III), d6, 18e
RhH2Cl(PPh3)3
Rh(III), d6, 18e
2
4) Ortho metallation, cyclo metallation
5) -hydride elimination
RuH2(PPh3)4 + 2KCl + 2 acetone
Ru(II), d6, 18e
RuCl2(PPh3)4 + 2KOCH(CH3)2
Ru(II), d6, 18e
PMe2
PMe3
W
H
PMe
PMe3 3
W[P(CH3)3]6
W(0), d6, 18e
W(II), d4, 16e
Reactivity of hydride complex
1) H-
2) H.
O
R
H
Cp2Zr
Cl
Zr(IV), d0, 16e
R
OCHR2
Cl
Cp2Zr
Zr(IV), d0, 16e
O
Zr(IV), d0, 16e
[Co(CO4)]- + H+
Co(-I), d10, 18e
2[Co(CN5)]3-
Co(II), d6, 18e
Co(II), d7, 17e
+
OCH2CH3
Cl
Cp2Zr
3) H+
2[HCo(CN5)]3- +
4) insertion to alkene and alkyne
5) H2 elimination
HCo(CO4)
Co(I), d8, 18e
5.3 molecular hydrogen complex
H
H
Cy3P
CO
W
OC
PCy3
CO
W(0), d6, 18e
H
H
R3P
PR3
Ru
R3P
H
H
H
H
OC
CO
Cr
OC
CO
CO
Ru(II), d6, 18e
weak back donation to hydrogen
Cr(0), d6, 18e
5.4 agostic interaction
agostic interaction: interaction of a coordinately-unsaturated transition metal with a C-H bond
(two electrons involved in the C-H bond enter the empty d-orbital of a transition metal, resulting in a two electron three center bond)
ex)
H
P Cl
H
P Ti
H
Cl Cl
P Cl
P Ti
Cl Cl H
-agostic interaction
6.
H
H
-agostic interaction
donation,
back-donation
6.1 carbonyl complex
ex)
M
dM
M
C O
n,
HOMO
donation
dM
C O
n,
O
OCC CO
CO
OC Co Co CO
OC
CO
CO
Ni CO
OC
CO
LUMO
back-donation
...etc
6.2 nitrocyl complex
Ln-1M
M
-
NO
N O
LnM
+
N O
CO equivalent
6.3 molecular nitrogen complex
M
NO
N O
LnM+
basic metal
end-on
O
N
Ph3P
NO
Ir
Cl
PPh3
Ph3P Ru NO
Cl
PPh3
6.4 molecular oxygen complex
(H3N)5Co O
O Co(NH3)5
N
N
Zr
N
Zr N
N N
ex)
5+
PPh2Et
OC
O
Ir
Cl
O
PPh2Et
6.5 molecular carbon dioxygen complex
M O C O
1
-O
high oxidation
metal
O
O
M C
O
-C,O
1
C
O
M
2
-C
low oxidation
metal
3
6.6 phosphine complex
basicity: PR3> PR2Ar> PRAr2> PAr3
acceptor ability: NO> CO> RNC> PF3> PCl3> PCl2R> PBr2R> P(OR)3> PR3> RCN> RNH2> NH3
X
M
d - * interaction
P
X
X
d - * interaction
a. Structural factor
Tolman cone angle: measure of size of ligand
bite angle: bidentate ligand
P
P
M
P
M
Table 9-7
Table 9-8
b. electronic factor
(R3P)Ni(CO)3: there is a strong correlation between
CO
and electron donating ability of phosphine ligand.
Table 9-9
6.7 carbene complex
Fisher carbene: electrophilic carbene
low oxidation state
middle and late transition metal
-acceptor ligand
-donor substituents on methylene
Schrock carbene: nucleophilic carbene
high oxidation state
early transition metal
-donor ligand
hydrogen and alkyl substituents on carbenoid carbon
R
LnM C
R
R
R
LnM C
R
LnM
R
R
Me
Ta
H
OMe
OC
CO
W
OC
CO
CO
Tebbe complex
H
W(II), d4, 18e
0
Ta(V), d , 18e
synthesis of carbene complex
Ta(CH3)3(OAr)2
Me
(C5H5)2Ta
Me
hv
W(CO)6
Ta(=CH2)(CH3)(OAr)2
BF4- + CH2=P(CH3)3
(C5H5)2Ta
PhLi
(OC)5W
OLi Me O+
3
(OC)5W
Ph
OMe PhLi
Ph
(OC)5W
Ph
Ph
Cl
Cl OEt
EtOH
Cl Pt CNC6H5
Cl Pt
PPh3
PPh3 NHC6H5
CH2
Me
Me
H
Me
1-C10H7
(OC)5W
N
N
H
Me
1-C10H7
N
N
W(CO)6 +
H
H
Me
1-C10H7
1-C10H7
7. -bonding ligand
7.1 alkene complex
Cl Pt Cl
Cl
Dewar-Chatt-Duncanson model
Cl
Rh Rh
Cl
C
C
M
dM
,
M
donation
C
C
high oxidation state
C
C
M
dM
*
,
M
back-donation
C
C
anionic complex
electron donating ligand
4
7.2 alkyne complex
Dewar-Chatt-Duncanson model can be applied to alkyne complex.
O
Ph
O
R
(OC)3Co Co(CO)3 +
OC Mn
OC
R
R
R
(OC)3Co Co(CO)3
Ph
7.3 -allyl complex
HB
HA
HB
95~120°
HA
HA: anti
HB: syn
M
dyz
dz2
syn-anti isomerization
HB
HA
allylic rotation
HB
HB
HA
HA
M
HB
HA M
M
M
HB
HA
HA
HB
HA
HB
HA
HB
L1 Mo
L2
L1 Mo
L2
cf) crotyl complex: racemization, 1,3-disubstituted allylic complex: syn-anti isomerization
7.4 diene complex
molecular orbital (figure 9-20)
M
M
diene
metallacyclopentene
back donation
Zr, Ta, Nb
R1
Zr
R1
Zr
racemic
R2
R2
(CO)3Fe
R1
(CO)3Fe
R2
Zr
Zr
R1
R2
R1
R2
R1
R1
R2
(CO)3Fe
R2
7.5 cyclopentadienyl complex
3
-indenyl
M
ex) ferrocene 18e
cobaltcene 19e
nickellocene 20e
M
M
5
-C5H5
1
-C5H5
Cl
Ti
Cl
Ti(IV), d0, 16e
electrophilic
Cp*= C5(CH3)5
metallocene
(figure 9-22)
Cl
Ta Cl
Cl
Ta(V), d0, 18e
H
Mo
H
Mo(IV), d2, 18e
nucleophilic
synthesis of cyclopentadienyl complex
1) metal salt + cyclopentadienyl anion
FeCl2 + 2C5H5Na
(C5H5)2Fe + 2NaCl
2) redutive condition
RuCl3 + 3C5H6 + 1.5Zn
(C5H5)2Ru + C5H8 + 1.5ZnCl2
5
7.5
OC
benzene complex
Cr CO
CO
Cr(0), d6, 18e
Cr
Fe
Cr(0), d6, 18e
F(II), d6, 18e
figure 9-24
synthesis of arene complex
1) arene + metal salt
CrCl3 + 2C6H6 + 1/3AlCl3 + 2/3Al
Cr
Na2S2O4
AlCl4-
Cr(I), d5, 17e
Cr
Cr(0), d6, 18e
2) ligand exchange
Mo(CO)6 +
OC
Mo CO
CO
Mo(0), d6, 18e
3) hydrogen extraction from cyclohexadiene
RuCl3 +
Cl
Ru Cl
Cl Ru
Cl
Ru(II), d6, 18e
L
L
Mo Cl
Cl
Ru(II), d6, 18e
6