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Issue 19, 1998
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Kinetics and mechanism of the cobaloxime(II)-catalysed oxidative dehydrogenation of 3,5-di-tert-butylcatechol by O2. A functional oxidase model

Abstract

Triphenylphosphinecobaloxime(II) has been found to be a selective catalyst for the oxidative dehydrogenation of 3,5-di-tert-butylcatechol to the corresponding 1,2-benzoquinone at room temperature and atmospheric dioxygen pressure. In a rapid initial phase the catalyst is reversibly transformed to a previously characterised catecholatocobaloxime(III) species, which persists throughout the reaction, keeping CoII at a low level. The semiquinone anion radical (dbsq˙–) and its cobaloxime(III) complex CoIII(dbsq˙–) have been detected as intermediates by ESR spectroscopy. The kinetics was followed by volumetry. According to the proposed mechanism, in the rate-determining step superoxocobaloxime (CoIIIO2) abstracts an H atom from the cathechol via an hydrogen-bonded intermediate. The system investigated is a functional model of catecholase (oxidase) activity, based on free-radical intermediates, a possibility recently demonstrated for certain oxidoreductases.

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Article type: Paper
DOI: 10.1039/A803597K
Citation: J. Chem. Soc., Dalton Trans., 1998, 3275-3280
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    Kinetics and mechanism of the cobaloxime(II)-catalysed oxidative dehydrogenation of 3,5-di-tert-butylcatechol by O2. A functional oxidase model

    L. I. Simándi and T. L. Simándi, J. Chem. Soc., Dalton Trans., 1998, 3275
    DOI: 10.1039/A803597K

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