Organo-metallics:-

Bond between metal and carbon of organic molecule.

Sodium ethoxide is not organo metallic as sodium is linked with oxygen.

1. σ–Bonded:-

Metal is directly attached with carbon using –bonded.

e.g:- CH₃ – Li, (C₂H₅)₄ Pb, R₃Al, R-MgX

Grignard Salt:-

2..π – Bonded:-

π-Bond between two atoms is co-ordinated towards vacant d-orbital of metal by using delocalization.

eg:- Ferrocene

Bis (Benzene Chromium) 

3..

1. σ and π Both Bond:-

contain vacant anti-bonding molecular orbitals. Therefore they can show synergic effect.

These legands donate their lone pair as sigma bond towards vacant d-orbital of metal and filled d electrons of metals are delocalized in anti-bonding -orbitals of legands. Such legand -donor and -acceptor legand -acid legand. Therefore they form most stable complexes.

CO is best -acceptor and CN^- is best -donor and poor -acceptor compared to CO.

1. [Ni (CO)₄ ] ------==> Sp³
2. [Fe (CO)₅ ] -----==> dSp³
3. [Cr (CO)₆ ] ------==> d²Sp³

Since carbonyl accept electron in its anti-bonding orbital. Its bond order is slightly decreased. And bond length is slightly increased.

• Strongest metal carbon is present in:-

1. [Ni (CO)₄ ]           
2. [Cr (CO)₆ ]
3. [Mn (CO)₆ ]⁺
4. [V (CO)₆ ]^-

Ans:- 4) [V (CO)₆ ]^-