An extension of the CNDO/2 formalism for the study of transition metal complexes

A previously described extended CNDO/2 method is used for investigating the energy level distribution and electronic structure of trifluorophosphine metal complexes: Cr(PF₃)₆, Fe(PF₃)₅, Ni(PF₃)₄. The results are compared with the few experimental data which are known for these complexes. The metal-phosphorus bonds show large (P M) and (M P) charge transfers but small total charge transfers (M P) which induce on the metal in any case a small positive charge.Such ( + ) coordination bonds seem to be generally characterized by small bond overlap populations (or small Wiberg indices).