Electroprotic phenomena and metal oxidation states

Abstract

A ubiquitous reaction in transition metal chemistry is electron transfer deriving from the variable valence capability of the metal center. When the coordinated ligand has one or more potentially labile protons, electron transfer at the metal (M) may proceed with symbiotic proton transfer at the ligand (L), Such a coupled transfer will be called an electroprotic reaction. An important extension of Fig. 1 can be the transfer of externally added redox equivalents to the ligand via the metal thereby effecting a metal-catalyzed electroprotic transformation of the ligand. The scope of electroprotic phenomena is obviously wide and spans many reactions in chemistry and biology. This Comment has the limited objective of recounting some of our personal experiences in this fascinating field which we gained in the course of our dealing with the synthetic chemistry and redox activity of multiple oxidation states of copper, nickel, ruthenium, and molybdenum.