Bond Valence Sum: A Powerful Tool for Determination of Oxidation States of Metal Ions in Coordination Compounds

Transition metal ions in coordination compounds can adopt different oxidation states. The Bond Valence Sum (BVS) model, based solely on structural information, relates the bond lengths around a metal center to its oxidation state. This model can provide details on the oxidation states of the metal ions and serves as an additional support for the accuracy of crystal structure determination. Herein, we introduce the fundamental concept of the BVS method and summarize the empirical BVS parameters for selective metal ions that have more than one oxidation state. Applications of the method to mononuclear and polynuclear complexes will be discussed.