The complexes with ligands carbodiphosphorane-analogues (called tetrylones) [(CO)5 W-{E(PH3)2] (W5-EP2) and N-heterocyclic carbene-analogues (called tetrylenes) [(CO)5 W-{NHEMe}] (W5-NHEMe) when E = C - Pb have been studied using natural bond orbital (NBO) method. The NBO analysis provides a consistent picture of the chemical bonding is two entire families of transition metal complexes oftetrylone and tetrylene ligands in term of donor-acceptor interactions, showing the correlation of these interactions with Wiberg bond indies (WBI), natural partial charges, and the energetically highest lying occupied molecular orbitals for delta and pi orbitals of nee ligands E(PH3)2 and NHEMe. Analysis of the bonding situation reveals that in E(PH3)2 and NHEMe ligands, the energy level of the pi orbital rises, whereas that of the delta orbital decreases as atom E becomes heavier. The complexes with head-on-bonded ligands have (CO)5W - E donation which comes from the delta-lone-pair orbital of E(PH3)2 and NHEMe where E