Question

Out of NH₃ and CO, which ligand forms a more stable complex with a transition metal and why?

Answer 1

Out of NH₃ and CO, CO ligand forms a more stable complex with transition metal because the metal-carbon bond in metal carbonyls possesses both s and p character. By the donation of lone pair of electrons of the carbonyl carbon into a vacant orbital of the metal, the M–C σ bond is formed. Similarly, the M–C π bond is formed by the donation of a pair of electrons from a filled d-orbital of metal into the vacant antibonding π orbital of carbon monoxide. This metal-ligand bonding creates a synergic effect that is responsible for the strengthening of the bond between CO and the metal.