In which compound synergic effect is present?

Step-by-step solution

Synergic effect is defined as the increase in bond strength of the metal-carbonyl bond in a metal carbonyl. This is a special case of backbonding in which not only does the carbonyl ligand donate electrons to the metal atom through a sigma bond, but also the metal atom donates an electron pair from its filled d -orbitals into the vacant antibonding π -orbital of CO . This pi-bond formation strengthens the M - C , σ - bond, and this increase in strength is called the synergic effect. Therefore, synergic ef