New Insights into the Structures and Reactions of Chromium(V) Complexes: Implications for Chromium(VI) and Chromium(V) Oxidations of Organic Substrates and the Mechanisms of Chromium-Induced Cancers

Cr(V) complexes have been shown to undergo a variety of reactions including geometric isomerism, coordination number changes, solvation, ligand exchange and dimerisation. Normally these reactions are rapid compared to the subsequent reduction of Cr(V) by organic substrates, or disproportionation of Cr(V) to Cr(VI) and Cr(III). Many of these rapid pre-equilibrium processes that precede the redox chemistry have been overlooked previously in developing mechanistic schemes for Cr(VI) and Cr(V) oxidations of organic and inorganic substrates. As outlined here, this will require a reinterpretation of much of the published mechanistic details on Cr(VI) and Cr(V) redox reactions. The new results also have substantial implications for understanding possible mechanisms of Cr(VI)-induced cancers, and controlling the selectivity of Cr(VI) oxidations of organic substrates.