Organometallic compounds are defined by the presence of metal-carbon bonds and exhibit unique bonding characteristics that differ from ionic or classic covalent bonds. The effective atomic number and the 18-electron rule are key concepts in understanding their stability, with examples including various metal carbonyls like hexacarbonylchromium(0) and pentacarbonyliron(0). These compounds have diverse applications in areas such as catalysis, pharmaceuticals, and materials science.

1. MFD 1
Organometallic Chemistry
An organometallic compound is generally
defined as one that possesses a metal and
carbon bond.
M C

2. MFD 2
Organometallic chemistry
M C
H C
< 2.0 2.5
2.2 2.5
The electronegativity
of metal is generally
less than 2.0 on a
Pauling's scale.

3. MFD 3
H C
M C
Organometallic chemistry

4. MFD 4
M C
H C
Organometallic chemistry
The dipole separation
is more incase of
metal-carbon bond
where carbon is more
nucleophilic and
basic.

5. MFD 5
Organometallics Compounds
• pharmaceuticals
• agrichemicals
• flavors
• fragrances
• semiconductors
• ceramic precursors
• catalysis

6. MFD 6
Bonding in organometallic compounds
• Ionic Compounds of Electropositive
Metals
(C6H5)3C-
Na+
and (C5H5)2
2-
Ca2+
• σ-Bonded Compounds
(CH3)3SnCl
• Non-classically Bonded Compounds

7. MFD 7
Bonding in organometallic compounds
• Non-classically Bonded Compounds
In many organometallic compounds there is a type of metal-carbon bonding that cannot be explained in terms of ionic
or electron-pair a bonds.
Alkyls of Li, Be, and Al that have bridging alkyl groups-electron deficiency and the bonding is of a similar multicenter type.
Compounds of transition metals with alkenes, alkynes, benzene, and other ring systems such as C6H5
-
.

8. MFD 8
Effective atomic number
The sum of the electrons on the metal plus the electrons donated from the ligands was
called the effective atomic number (EAN), and when it was equal to 36 (Kr), 54 (Xe), or
86 (Rn) the EAN rule is said to be obeyed.
Cr(Z=24) total electrons of chromium = 24 e-
Six Terminal CO (6 X 2e- ) = 12 e-
Total = 36 e-
Comment on stability of hexacarbonylchromium(0) based on EAN.
Cr(CO)6 is stable as chromium achieve effective noble
gas formalism as that of Kr (Z=36).

9. MFD 9
18 Electron Rule
The number of valence electrons for the noble gases is 18, the noble gas formalism may be
simplified to the 18-electron rule. The stable metal complexes will be those which, in
acquiring electrons from ligands, attain a total of 18 electrons.
metal valence electrons + donated ligand electrons and other atoms
Cr(Z=24)- [Ar] 3d4
, 4s2
= 6 e-
Six Terminal CO (6 X 2e- ) = 12 e-
Total = 18 e-
Cr(CO)6 is stable as it follows 18 electron rule
Comment on stability of hexacarbonylchromium(0) based on 18 electron rule.

10. MFD 10
Types of metal carbonyls -mononuclear
Pentacarbonyliron(0)
(M=V or Cr)
hexacarbonylmetal
tetracarbonynickel(0)

11. MFD
Types of metal carbonyls-polynuclear
tetra-μ-carbonyl-1:2κ4
C,1:3κ2
C,2:3κ2
C-octacarbonyl-1κ3
C,2κ3
C,3κ2
C-triangulo-triiron(3 Fe—Fe)
Dimanganese decacarbonyl
bis(pentacarbonylmanganese)(Mn—Mn)
Dicobalt octacacarbonyl
bis(tetracarbonylcobalt)(Co—Co)
Diiron nonacarbonyl
tri-μ-carbonylbis(tricarbonyliron)(Fe—Fe)
Dodecarbonyltriiron

12. In order to have a vanadium carbonyl
that satisfies the noble gas formalism,
what would be the simplest formula?
Why do you think this fails to occur?

13. Preparation of metal carbonyl
MFD
Ni + 4 CO
RT, 1atm
Ni(CO)4
Fe + 5 CO
200 °C, 200 atm
Fe(CO)5
UV, hν
Fe2(CO)9
Mn(acac)3 + 10 CO
(C2H5)3Al
Mn2(CO)10
C6H5MgBr
Cr(CO)6
CrCl3 + 6 CO
CoCO3 + 2H2 + 8 CO
250-300 atm
Co2(CO)8 + 2CO2 + 2 H2O

14. Metal carbonyls and their Properties
MFD
Mx(CO)y Properties
V(CO)6 Form Black crystals; decomposes 70 °C; sublimes in vacuum, Octahedral, Yellow
orange in solution; paramagnetic
Cr(CO)6 Colorless crystals; sublime in vacuum, Octahedral Stable to air; decompose 180-
200 °C
Fe(CO)5 Yellow liquid, mp -20 °C bp 103 °C , trigonal bipyramid, Action of UV gives
Fe2(CO)9
Mn2(CO)10 Yellow solid, mp 151 °C, sublimes 50 °C, The Mn—Mn bond is long (2.93 A) and
Mn2(CO)10 is reactive
Fe2(CO)9 Gold solid mp 100 °C decomposes Very insoluble and non-volatile
Fe3(CO)12 Green-black solid, mp 140-150 °C decomposes,
Co2(CO)8 red-orange crystal, 52 °C decomposes,

15. MFD
Types of metal carbonyls-polynuclear
tetra-μ-carbonyl-1:2κ4
C,1:3κ2
C,2:3κ2
C-octacarbonyl-1κ3
C,2κ3
C,3κ2
C-triangulo-triiron(3 Fe—Fe)
Dimanganese decacarbonyl
bis(pentacarbonylmanganese)(Mn—Mn)
Dicobalt octacacarbonyl
bis(tetracarbonylcobalt)(Co—Co)
Diiron nonacarbonyl
tri-μ-carbonylbis(tricarbonyliron)(Fe—Fe)
Dodecarbonyltriiron