According to the synergic bonding model in metal carbonyls, metal-to-ligand -back donation has what — Coordination Compounds Chemistry Question

💡 Solution & Explanation

$\pi$ -back donation from filled metal d-orbitals pushes electron density into the empty $\pi^*$ antibonding orbital of the CO ligand. This weakens the C-O bond, decreasing its bond order and increasing its bond length.