The electronic structure of transition metal complexes containing organic ligands

Abstract
All electron ab initio SCF MO calculations of Cr(C6H6)2 and C6H6Cr(CO)3 are described. In both complexes the benzene ligand bears a net negative charge and in the carbonyl complex the -CO ligands accept more electron density than in unsubstituted carbonyls. The He(I) and He(II) p.e. spectra of both complexes are reported and interpreted with the aid of these calculations. For ionization from mainly ligand MO's, Koopmans' theorem allows a satisfactory interpretation of the measured I.P.'s and the change in intensity between He(I) and He(II) spectra may be correlated with the atomic orbital character of the M.O.'s. However, for ionization from these MO's having substantial metal character the relaxation energy is dependent upon their degree of localization and direct calculation of the energy of the ion states is necessary to interpret this region of the p.e. spectra.