Molecular Orbital Theories of Inorganic Complexes

Abstract

This chapter discusses the semi-empirical and semi-quantitative methods, which have been used in molecular orbital calculations on transition metal complexes. It is contended that the extended Wolfsberg-Helmholz method forms a rational basis for semi-empirical calculations, but like semi-empirical methods in other fields, it should be used with care, and only the gross features of the results should be considered to be meaningful. An analysis of semi-quantitative methods led to the conclusion that the only completely consistent method uses the CNDO (complete neglect of differential overlap) approximation. The CNDO method is applied to the permanganate ion, through which conclusions are drawn concerning the bonding and the electronic spectrum for the ion, without introducing semi-empirical factors that are abundant in calculations on transition metal complexes.