The metal-carbon bond in metal carbonyls
possess both s and p character The M–C s bond
is formed by the donation of lone pair of electrons
on the carbonyl carbon into a vacant orbital of
the metal The M–C p bond is formed by the
donation of a pair of electrons from a filled d orbital
of metal into the vacant antibonding p*
 orbital of
carbon monoxide The metal to ligand bonding
creates a synergic effect which strengthens the
bond between CO and the metal (Fig