Question -
Answer -
Themetal-carbon bonds in metal carbonyls have both σ and π characters. A σ bond isformed when the carbonyl carbon donates a lone pair of electrons to the vacantorbital of the metal. A π bond is formed by the donation of a pair of electronsfrom the filled metal d orbital into the vacant anti-bondingπ* orbital (also known as back bonding of the carbonyl group). The σ bondstrengthens the π bond and vice-versa. Thus, a synergic effect is created dueto this metal-ligand bonding. This synergic effect strengthens the bond betweenCO and the metal.
