Bond Order Conservation Principle and Peculiarities of the Metal-Metal Bonding

Pauling's principles developed later in the bond valence model (BVM) are fundamental in description of bonding in ionic solids and surface phenomena on metals, but applicability of these principles to the metal-metal bonds in the bulk compounds was demonstrated only recently, with a spotlight on the bond valence-bond length correlations. This work is focused on the bond order conservation in cluster compounds and determination of empiric bond valence parameters for the metal-metal bonds, which ensure very simple and reasonably accurate bonding analysis, with zero cost, in any complex cluster compound. Such peculiarities of cluster compounds as matrix effect and nonuniform distribution of the ionic charges (bond valence sums) on the ligands around metal clusters, as well as other important examples of the BVM application to compounds with metal-metal bonds, are discussed.