The Reduction of Dioxygen by Keggin Heteropolytungstates

Abstract

AbstractReversible redox chemistries are an inherent feature of numerous metal oxide cluster anions (POMs). Moreover, as discrete molecular structures with well‐defined and controllable solution chemistries, POMs can be deployed as physicochemical probes for studying inorganic reaction mechanisms. In the past decade, we have used an iso‐structural series of α‐Keggin heteropolytungstate cluster anions to systematically investigate a number of fundamental topics, including electron transfer to dioxygen. The iso‐structural series of cluster anions is obtained by varying the heteroatom, Xn+, in the plenary, Td‐symmetry α‐Keggin ion, Xn+W12O40(8−n)−, from Al3+ to Si4+ to P5+. This results in a stepwise and linear modulation of ion charge and reduction potential, whose concerted effects on reaction rates can be used to better understand electron‐transfer processes. Starting from the acquisition of activation parameters associated with electron self‐exchange between the POMs themselves, the studies discussed in this review provide a detailed account of electron transfer from reduced α‐Keggin heteropolytungstate anions to dioxygen, culminating in the recent discovery of a fundamentally new mechanism for electron transfer to O2 in water.