Equilibrium and Kinetic Studies of the Peroxo Complex of Molybdenum(VI) in Acidic Perchlorate Solution

摘要

Molybdate is commonly used as a catalyst in the iodometric determination of hydrogen peroxide. A detailed kinetic study of this system in acidic solution has been reported. It was proposed that a diperoxo complex of molybdenum(VI) was the reactive species toward iodide. Peroxo complexes of molybdenum(VI) have bee n used as oxidants for organic substrates and are implicated as intermediates in the catalyzed epoxidation of olefins by alkyl hydroperoxides. A number of crystal structures of peroxomolybdenum(VI) complexes have been reported, and solution studies of the complexes have been reviewed. We have studied the redox chemistry of peroxo complexes of several d superscript 0 transition-metalions and compared the results to the corresponding reactions of hydrogen peroxide. An important objective of this work is to increase our understanding of how metal ions modify the reactivity of peroxide. The advantage in using d superscript 0 transition-metal ions is their ability to rapidly form peroxo complexes with large formation constants. We have recently turned our attention to molybdenum(VI) and are finding that its peroxo complex is markedly more reactive than hydrogen peroxide toward a number of simple substrates. In this paper we report the results of spectrophotometric studies of the equilibrium between hydrogen peroxide adn molybdenum-(VI) in acidic perchlorate solution. In addition, we have measured the kinetics of formation and dissociation of the peroxo complex by use of the stopped-flow procedure. (Reprints)