Question

Π acid ligand which uses d orbital for synergic bond

Answer 1

The back donation reinforce the sigmabond, and vice versa. This type ofbonding has been called the synergic bonding.

It is generally observed in metal carbonyls. In these complexes, CO behaves as ligand and donates electrons to empty orbitals of metal atom to form sigma bond.

Metal atom donates d - orbital electrons to ABMO of CO which is an empty orbital to form pi bond