Question

Write short notes on bonding in metal carbonyls.

Answer 1

The metal-carbon bonds in metal carbonyls have both $\sigma$ & $\pi$ characters.

A $\sigma$ bond is formed when the carbonyl carbon donates a lone pair of $e^{-}$ to the vacant orbital of the metal.

A $\pi$ bond is formed by the donation of pair of electrons form the filled metal d-orbital into the vacant anti bonding $\pi$-orbital. It is known as back bonding of the carbonyl group.

The $\sigma$ bond strengthens the $\pi$ bond & vice-versa. Thus a synergic effect is created due to this metal-ligand bonding. It strengthens the bond between $CO$ & the metal.