Studies on the coordinated dioxygen species produced from the photoproducts of alkylcobaloximes in aqueous solution

Abstract

The reactions of' molecular oxygen with photoproduced cobaloximes(II) from the cobalt(III) complexes [CH₃Co(DH)₂Pyj, <b>1</b> and [C₂H₅Co(DH)₂Py], <b>2</b> (where DH is dimethylglyoxime and py is pyridine) have been investigated by flash photolysis methods. The reaction of cobaloxime(II) with molecular oxygen to give mononuclear superoxocobalt(IIl) species is the first step. The reactions to form the <i>m</i>-superoxo cobalt(III) complex from the mononuclear superoxo complex and the alkyl cobalamine( III), and the formation of the <i>m</i>-peroxo cobalt(III) complex directly by the reaction between mononuclear superoxo complex and the photoproduced cobalamin(II) and by the conversion of <i>m</i>-superoxo complex are the subsequent processes observed. The rate constants determined for these reactions are discussed based on a scheme indicating all the reactions. The results show that the reaction between the mononuclear superoxo complex and the photoproduced cobalamin to give the <i>m</i>-peroxo complex is faster than the reaction involving formation of the <i>m</i>-superoxo complex from the mononuclear superoxo complex.