Counting electrons and rationalizing structures of clusters and clusters of clusters

Abstract

The investigation of the electronic structures of high nuclearity metal clusters constitutes an important prerequisite for the basic understanding of the relationship between discrete metal clusters and the extended bulk metal. Simple electron counting principles are particularly useful in this regard. It not only allows a systematization or rationalization of the observed structures of these clusters, but also can lead to prediction of clusters of yet unknown molecular architectures and/or formulations. In this review, electron counting principles for the metal clusters of varying nuclearity (magic numbers), size, shape and packing arrangements will be discussed. Emphasis will be focused upon: (1) the topological electron counting ( TEC) rule; (2) the C 2 model for clusters of clusters; (3) the Shell model for v n polytopal close-packed metal clusters; and (4) the Extended Hume-Rothery rule for metal clusters of close-packed arrangements.