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Organometallic Chemistry
Chem 432
Outline
Bonding
The 18-electrons rule
Hapticity
Isolobal relationships
Metal carbonyl complexes
Metal nitrosyl complexes
Metal hydride complexes
Alkyl and acyl metal complexes
Metal alkene and alkyne complexes
Ligands with delocalized p bonding
metallocenes
Scorpionates
Why octahedral complexes obey the 18-electron rule
eg
t2g
d
6 ligands
12 electrons
Why square planar complexes tend to have 16 electrons
M.C. White, Chem 153
η1 ligands
Formal
charge
(monodentate):
Common
Ligands
# of edonated
Hap
H (hydride)
-1
2
CH3 (alkyl)
-1
2
CO
0
2
X (halides)
-1
2
µ-X (bridging)
-1
M
X
to th
4
(2/metal)
M
OR (terminal
-1
2
-1
4
alkoxide)
µ-OR (bridging)
M
R
O
(2/metal)
M
OR2 (ether)
0
2
O 2 (superoxide)
-1
2
O (terminal oxo)
-2
4
µ-O (bridging)
-2
M
M.C. White, Chem 153, Harvard University
Structure &
O
4
(2/metal)
M
PR2 (phosphide)
-1
2
PR3 (phosphine)
0
2
NR2 (amide)
-1
2
NR3 (amine)
0
2
imines
0
2
nitriles
0
2
+1
2
NO (nitrosyl )
linear
Pro
ally
Brid
Hapticity
Monohapto Ligands
J. Chem. Ed. 1990, vol 67, p. 294
Polyhapto Ligands
J. Chem. Ed. 1990, vol 67, p. 294
M.C. White, Chem 153, Harvard University
Unsaturated
Ligands
Unsaturated
Ligands
Unsaturated
Ligands
M.C. White,
153
M.C.Chem
White,
Chem 153
StructureStructure
& Bonding
-10& Bonding
-10-
Formal
η1-coordination
η1-coordination charge
M
η 1-aryl
M
-1
# of eFormal
# of edonated donated
charge
-1
2
Formal
ηx-coordination
ηx-coordination charge
2
M
η6-arene
η 1-aryl
-1
-1
2
M
η2-alkene
η1-alkynyl
M
η1-alkynyl
-1
-1
2
2
-1
-1
2
2
-1
-1
2
2
M
M
η 1-Cp (cyclopentadienyl)
η 1-Cp (cyclopentadienyl)
M
M
η 1-allyl
O
O
O
M
0 6
6
0
0 2
2
0
0 2
2
-1
-1 6
6
-1 4
4
-1 4
4
M
H
M
M
η2-alkyne η2-alkyne
H
H
η 1-allyl
0
η2-alkene
RH
R
RM
# of eFormal
# of edonated donated
charge
M
η6-arene
2
M
M
η1-alkenyl η1-alkenyl
R
Week of Week
September
17, 2002 17, 20
of September
O
η1-acetate η1-acetate
M
M
M
η5-Cp (cyclopentadienyl)
η5-Cp (cyclopentadienyl)
M
M
M
=
η3-allyl
η3-allyl
O
O
M
-1
-1
2
2
MM
=
-1
M
M
O
O
η2-acetate η2-acetate
-1
Isolobal Relationships
LnM
dn
CHm
L2M
10
CH2
L3M
9
CH
L4M
8
CH2
L5M
7
CH3
L5M
6
CH2
L5M
5
CH
L6M
5
CH3
L4M
9
CH3
L3M
10
CH2
J. Chem. Ed. 1990, vol 67, p. 294
Isolobal Relationships
CH3
Cr(CO)3Cp
Mn(CO)5
CH2
Cr(CO)5
Mn(CO)2Cp Fe(CO)4
Co(CO)Cp Ni(CO)2
CuCp
CH
Cr(CO)2Cp
Mn(CO)4
Fe(CO)Cp
Co(CO)3
NiCp
Cu(CO)2
C
Cr(CO)4
Mn(CO)Cp
Fe(CO)3
CoCp
Ni(CO)
J. Chem. Ed. 1990, vol 67, p. 294
Fe(CO)2Cp
Co(CO)4
Ni(CO)Cp
Cu(CO)3
Metal Carbonyl Complexes
Preparation
Metal Carbonyl Complexes
Structure
Metal-Carbonyl Bonding
s donation
M
p back-bonding
M
C
C
O
O
Metal- Bridging Carbonyl Bonding
s donation
O
C
M
M
p back-bonding
O
C
M
M
terminal
bridging
µ2
bridging
µ3
Modes of bonding
M
p
Modes of bonding
Modes of bonding
Modes of bonding
Metal Nitrosyl Complexes
Preparation
NO+ is isoelectronic and isolobal with CO
Metal Nitrosyl Complexes
Structure
Metal Hydride Complexes
Preparation
Reaction with hydroxide or borohydride anions
Metal Hydride Complexes
Preparation
Protonation of the anion
Metal Hydride Complexes
Structure
Alkyl and Acyl Metal Complexes
Preparation
Nucleophilic Addition
alkyl
acyl
Alkyl and Acyl Metal Complexes
Preparation
Nucleophilic Addition
Alkyl and Acyl Metal Complexes
•
CO Insertion
Alkyl Metal Complexes
Structure
Acyl Metal Complexes
Structure
Metal Alkene Complexes
R2
C
C
M
R2
Zeise’s salt
Metal Alkyne Complexes
R
C
C
M
R
Metal Alkyne Complexes
O
Ligands with delocalized p bonding
three-legged piano stool
four-legged piano stool
Ligands with delocalized p bonding
Ferrocene
Discovered in 1951
x-ray structure in 1952
bis(η5-cyclopentadienyl)iron(II)
Orange solid
Catalyst for olefin polymerization
Metallocenes
two η5-cyclopentadienyl ligands bound to a metal
center
titanocene
vanadocene
Double Metallocenes
Fused cyclopentadiene (pentalene) ligands
Vanadium complex is h5
Nickel complex is h3
Iron does not form a double ferrocene
JACS 2008, vol 130, p. 15662
Carbon-Free Metallocene
Science 2002, vol 295, p. 832
Cyclobutadiene Ligands
Arene Ligands
Bonding with p donor ligands
2p and 3p ligand orbitals
usually have the best
match with M 3d orbitals
Scorpionates
Anionic tris(pyrazolyl)borate
ligands
Bind metal with N heteroatoms
from 2 pyrazole rings attached to
a central B
The 3rd pyrazole rotates forward
to ‘sting’ the metal
Scorpionates
Pyrazolyl borates provide large steric shielding of the metal
allow for reactivity on the other side of the metal
Nitrogen heterocycles other than pyrazole can be used
pyrrole, imidazole, indole, indazole.
Tripodal ligands can be multidentate with N, S, or P donor
atoms
Scorpionates
Ytterbium tetraphenylporphyrin
complex topped by a
tris(pyrazolyl)borate ligand
Polymer LED in near-IR
Luminesces under applied voltage
Writing can be seen with a nearIR camera
Scorpionates
Gold scorpionate complex
binds to ethylene
molecule
Potential for catalysis
Angew. Chem. 2007, vol 46, p. 7814