CBSE Class 12-science Answered

Pi-acceptor ligand is a ligand that donates a pair of electrons from a lone pair to the metal center but also has the ability to accept electron density from the metal d orbitals into either d orbitals or pi-antibonding orbitals. Low oxidation state complexes can be stabilized by using ligands such as cyanide and carbon monoxide because these ligands are pi-acceptor ligands and these ligands have the capability to donate a pair of electrons from a lone pair to the metal center but also has the ability to accept electron density from the metal d orbitals into either d orbitals or pi-antibonding orbitals. A ligand with ?-acceptor properties has unoccupied orbitals at energies well above the metal d_xy, d_xz, and d_yz orbitals with which mixing occurs to form ? and ?* orbitals. In this case, the ?* orbitals are localized on the ligand (not the metal). The former nonbonding d orbitals now become ? orbitals and are shifted to lower energies, thus increasing ?_o.