298 Abstracts DO31 VANADIUM(V)-CATALYZED OXIDATION OF BROMIDE BY HYDROGEN PEROXIDE: FUNCTIONAL MODELS OF VANADIUM BROMOPEROXIDASE Melissa Clague and A&on Butler Department of Chemistry, University of California, Santa Barbara, CA 93106 Vanadium bromoperoxidase catayzes the oxidation of bromide by hydrogen peroxide. This reaction is also catalyzed by a variety of oxovanadium(V) complexes with oxygen- and nitrogen-donor ligands in DMF solution and by VO, + in acidic aqueous solution [l]. A six- coordinate vanadium(V) complex, VO(HPS)(OEt)(EtOH), is shown to be a catalyst precursor in the oxidation of bromide by hydrogen peroxide. The acid dependence is characterized. We have established that catalysis requires an open coordination site in the equatorial plane, presumably for binding peroxide [2]. Complexes of bi- and tridentate ligands, some of which are shown in Figure 1, are the primary focus of this investigation. The stoichiometry of bromide oxidation is measured via the bromination of an organic substrate. Kinetic studies are performed by observing the formation of Br,‘ spectrophotometrically. Inhibitors of bromide oxidation are also being assessed. Using UV/vis spectrophotometry, 51VNMR spectroscopy, and kinetic data, a mechanism is proposed. The elucidation of the effects of ligand variation will lead to greater understanding of the electronic and steric factors which determine catalytic reactivity, and insight into the reactivity of vanadium in vanadium bromoperoxidase. 1. R.I. de la Rosa, M.J. Clague, A. Butler, J. Am. Chem. Sot., 1992, 114, 760. 2. M.J. Clague and A. Butler, in Advances in Inorganic Biochemistry, L.G. Marzilli and G.L. Eichhorn, Eds., in press. Figure 1 COOH OH H2HPS N-COOH COOH cooti

Vanadium(V)-catalyzed oxidation of bromide by hydrogen peroxide: Functional models of vanadium bromoperoxidase

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298 Abstracts

DO31 VANADIUM(V)-CATALYZED OXIDATION OF BROMIDE BY HYDROGEN PEROXIDE: FUNCTIONAL MODELS OF VANADIUM BROMOPEROXIDASE

Melissa Clague and A&on Butler Department of Chemistry, University of California, Santa Barbara, CA 93106

Vanadium bromoperoxidase catayzes the oxidation of bromide by hydrogen peroxide. This reaction is also catalyzed by a variety of oxovanadium(V) complexes with oxygen- and nitrogen-donor ligands in DMF solution and by VO, + in acidic aqueous solution [l]. A six- coordinate vanadium(V) complex, VO(HPS)(OEt)(EtOH), is shown to be a catalyst precursor in the oxidation of bromide by hydrogen peroxide. The acid dependence is characterized. We have established that catalysis requires an open coordination site in the equatorial plane, presumably for binding peroxide [2]. Complexes of bi- and tridentate ligands, some of which are shown in Figure 1, are the primary focus of this investigation. The stoichiometry of bromide oxidation is measured via the bromination of an organic substrate. Kinetic studies are performed by observing the formation of Br,‘ spectrophotometrically. Inhibitors of bromide oxidation are also being assessed. Using UV/vis spectrophotometry, 51V NMR spectroscopy, and kinetic data, a mechanism is proposed. The elucidation of the effects of ligand variation will lead to greater understanding of the electronic and steric factors which determine catalytic reactivity, and insight into the reactivity of vanadium in vanadium bromoperoxidase.

1. R.I. de la Rosa, M.J. Clague, A. Butler, J. Am. Chem. Sot., 1992, 114, 760.

2. M.J. Clague and A. Butler, in Advances in Inorganic Biochemistry, L.G. Marzilli and

G.L. Eichhorn, Eds., in press.

Figure 1

COOH

H2HPS

N-COOH COOH

cooti