Approximate self-consistent molecular orbital theory and calculation of iron enneacarbonyl

Abstract

The development of a pseudo atom model self-consistent field complete neglect of differential overlap (CNDO) molecular orbital theory and localized population analysis methods are described and applied to the iron enneacarbonyl electronic structure. In comparison to similar theories and treatments in other works, it is more general, has simpler derivation and computation procedures yielding reasonable results. Calculations have been made with these methods on the lowest singlet and lowest triplet state of Fe₂(CO)₉, the ground or lowest energy state is found to be the singlet, consistent with the diamagnetism of this molecule. The population analysis in the singlet case shows a total Fe-Fe bond order of 0.96 which is composed of sigma, pi and delta contributions of 0.68, 0.44 and -0.16, respectively.