Appreciation of electronic structures in some electron-rich octahedrally-based transition metal chalcogenide clusters

Abstract

Polynuclear nickel-chalcogenide cluster complexes play an important function at the active centers of many enzymes. Due to their importance in biological processes, these cluster compounds have attracted considerable interest, both experimentally and theoretically. Over the past decade, numerous synthetic nickel(cobalt) chalcogenide clusters have been made. Some selected examples are illustrated in 1-5, where E=S or Se; M=Co for 1 and 2; and M=Ni for 3-5). These clusters are all electron-rich, and their closed shell electronic structure requirements are not satisfactorily explained within the existing electron count rules. In this work, orbital interaction arguments have been developed to appreciate their electronic structures with the aid of extended Hückel molecular orbital calculations. Our approach is to first consider the local metal-ligand interaction