KINETICS AND MECHANISM INTRINSIC TO ELECTROREDUCTION OF THE MOLYBDENUM(VI) COMPLEXES WITH 8-HYDROXYQUINOLINE-5-SULFONIC ACID AT THE MERCURY-ELECTRODE

The kinetics and mechanism inherent in. electroreduction of the molybd enum(VI) complexes containing anions of 8-hydroxyquinoline-5-sulfonic acid (sulfoxine) are studied polarographically in aqueous solutions at pH 2 to 3. It is found that the reaction, proceeding in the region of the first reversible adsorption wave, yields binuclear hydroxy sulfox ine complexes of Mo(IV) adsorbed at the positively charged surface of the mercury electrode. In the region of the second wave with the limit ing diffusion current, there occurs irreversible two-electron reductio n yielding Mo(IV) complexes that pass into solution. The pH dependence of the half-wave potential of the adsorption wave is used to determin e the composition of the MoO2(OH)(H2O)L- complexes present in solution . The diffusion coefficient for these complexes is established on the basis of the limiting diffusion current.