About the topological classification of the metal–metal bond

Metal–metal bonds belong, from the topological point of view, to the wide class of the closed shell interactions proposed by Bader. Such a simple classification is, however, not satisfying in the description of these bonds and the nature of the metal–metal bond, in particular in polynuclear complexes, is debated. Using some topological and energy parameters, a comparison is made between polynuclear complexes and bulk metals and indicates the similar nature of these bonds.