Ab-Initio Molecular Orbital Studies of Structure and Reactivity of Transition Metal-OXO Compounds

Abstract

Ab-initio molecular orbital (m.o.) calculations were carried out to elucidate electronic structures and reactivities of transition metal-oxo compounds. It was found (1) that the oxygens in these complexes exhibit dual properties, electrophilic and nucleophilic, which are determined by the formal oxidation number of the transition metals and ligands involved and (2) that the diradical characters are not negligible for the weak π-bonds between transition metals and oxygens. The energy differences among the metal 1,4-diradical (MDR), zwitterion (MZW) and perepoxide (MPE) Intermediates were calculated to be not so large as in the case of singlet oxygen reactions. Thus the reaction mechanisms for epoxidations of olefins seem variable depending on the types of olefins and reaction conditions employed.