The M–C s bond results from the donation of lone pair electrons on the carbonyl carbon into a vacant orbital of the metal, while the M–C p bond arises from the donation of a pair of electrons from a filled d orbital of the metal into the vacant antibonding p* orbital of carbon monoxide. The metal-ligand bonding creates a synergic effect, reinforcing the CO-metal bond.
Explain the dual s and p character of the metal-carbon bond in metal carbonyls and the synergic effect contributing to bond strength.
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The metal-carbon bond in metal carbonyls exhibits dual s and p character, reflecting the overlap of the metal’s empty d orbitals with the π* antibonding orbitals of the CO ligands. The metal contributes s-character by donating electron density into the antibonding π* orbital of CO, enhancing bond strength. Simultaneously, p-character arises from the sideways overlap of the metal d orbitals with the π* orbitals of CO. This dual s and p character leads to a synergic effect, where the metal donates electron density to the ligand, and the ligand back-donates electron density to the metal, reinforcing the metal-carbon bond and influencing the overall stability of metal carbonyls.