Kinetics and mechanism of silver(I) catalyzed oxidation of coordinated formate by peroxydisulphate

Abstract

The oxidation of coordinated formate in the complexcis [Co(en)₂(NH₂R)(O₂CH)]²⁺ (R = H, Me or Et) by peroxydisulphate is catalyzed by Ag⁽¹⁾. Comparison between the rates of oxidation and of acid catalyzed equation of the formato complexes shows that the former is not substitution controlled. The observed pseudo first order rate constant was found to be first order with respect to the concentration of each of the reactantsi.e. the complex, Ag⁽¹⁾, and the oxidant. The rate and activation parameters for the oxidation process are reported. The major product of oxidation was found to be thecis(aquo)pentamine cobalt(III) [cis[Co(en)₂(NH₂R)OH₂]³⁺]; cobalt(II) was produced only <5%. The oxidation largely involves two electron transfer from the formate ligand, which is consistent with the hydride transfer mechanism.