EQUILIBRIA AND KINETICS OF THE REACTIONS BETWEEN HYDROGEN-PEROXIDE AND METHYLTRIOXORHENIUM IN AQUEOUS PERCHLORIC-ACID SOLUTIONS

In aqueous solutions the colorless compounds CH3ReO3 (=MTO) and H2O2 form 1:1 and 1:2 adducts. The latter is yellow, with epsilon360 = 1.1 X 10(3) L mol-1 cm-1. Peroxide binding to MTO shows cooperativity, as shown by the inversion of the usual order of binding constants. The stepwise equilibrium constants are K1 = 7.7 L mol-1 and K2 = 145 L mol-1 at 25-degrees-C. The buildup of product, which occurs on the stopped-flow time scale at 9-680 mM H2O2, is fit by biexponential kinetics. The equilibria and rates are independent of [H3O+] in the range 10(-1)-10(-3) M. The peroxide complexes decompose more rapidly at lower [H3O+], particularly at pH > 3. Possible structures for 1:1 and 1:2 MOT-H2O2 adducts are presented and discussed.