Mechanism of the coupled 24-electron reduction and transformations among the blues the browns and the reds of ammonium metatungstate

The complete mechanistic pathway for the 24-electron redox behavior of the metatungstate anion has been determined through the simulation of cyclic voltammetry data in low pH electrolytes. After the electrochemical reduction by up to four electrons, forming the tungsten-blues, coupled chemical and electrochemical reactions occur with increasing complexity upon further reduction of the metatungstate anion. Quantitative analysis of the data accounts for the formation of stable reduced tungsten-browns from the 6- and 12-electron reduced forms, and tungsten-reds from the 18- and 24-electron reduced forms. Published by Elsevier Ltd.