RUI: Halide Oxidation by Peroxometal Complexes: Mechanism and Reactivity

Colgate University, Hamilton NY

Investigators

Abstract

Dr. Martha Reynolds, Department of Chemistry, Colgate University, is supported by the Inorganic, Bioinorganic, and Organometallic Chemistry Program of the Chemistry Division for a study of the oxidation of halide ions by metal-bound peroxides. A series of new molybdenum(VI), vanadium(V), and tungsten(VI) peroxo complexes with ligands that vary systematically in their electron-donating properties will be synthesized and the reactivity toward bromide oxidation will be measured spectrophotometrically. These experiments will test the hypothesis that the electronic structure of a chelating ligand controls the strength of the peroxo bond in predictable ways, which in turn governs the reactivity of the complex as an oxidant. The reactivity of complexes that contain both peroxide and bromide or chloride directly bound to the metal will be examined. Such species represent possible intermediates in the peroxometal-mediated oxidation of halide ion. Because of the sensitivity of peroxo and metal-oxo vibrational frequencies to chemical changes, infrared spectroscopy will be used to obtain more detailed information on the mechanism of bromide oxidation and infrared-spectroelectrochemistry will be employed to compare the molecular details of the one- and two-electron oxidation chemistry of peroxometal complexes. Peroxide-containing metal complexes find application as catalysts for the oxidation or bromination of a variety of organic compounds. A biological example of such a catalyst is vanadium bromoperoxidase, an enzyme found in seaweed that produces oxidized bromine for the purpose of protecting the seaweed against predators or microorganisms. This project will provide an increased understanding of peroxometal complexes - and thereby of vanadium haloperoxidase enzymes - and holds promise for the development of new oxidation and bromination catalysts that may prove useful in the synthesis of anticancer, antimicrobial, and insulin-mimetic pharmaceuticals, and of oxidized or brominated organic compounds more generally. Students undertaking this research will gain facility in chemical synthesis, spectroscopic and electrochemical techniques, and chemical kinetics.