MECHANISTIC STUDY OF THE COORDINATION OF HYDROGEN-PEROXIDE TO METHYLRHENIUM TRIOXIDE

The activation parameters (DELTAH(double dagger), DELTAS(double dagger), DELTAV(double dagger)) for the co-ordination of hydrogen peroxide to methylrhenium trioxide have been determined. They indicate a mechanism involving nucleophilic attack. The protons lost in converting H2O2 to a co-ordinated eta2-O2(2-) group are transferred to one oxide oxygen, which remains on the metal as an aqua ligand. The rate of reaction is not pH dependent, consistent with the deuterium kinetic isotope effect (k(H)/k(D) = 2.8). The method used to study the reaction is based on the ability of ReMeO3 to catalyse the reaction between Br- and H2O2. The activation parameters for the uncatalysed reaction of Br- and H2O2 were also determined. The value found for DELTAV(double dagger) is consistent with the accepted mechanism, proton-assisted nucleophilic displacement.