Collect. Czech. Chem. Commun. 1986, 51, 1049-1060

Kinetics of oxidation of bis(ethylenediamine)mercaptoacetatocobalt(III) and cysteinatobis(ethylenediamine)cobalt(III) ions by peroxodisulphate in aqueous-nonaqueous mixed solvents

Oľga Vollárová, Ján Benko and Ivana Matejeková

Department of Physical Chemistry, Faculty of Sciences, Comenius University, 845 15 Bratislava


The kinetics of oxidation in the first step was studied for coordination-bonded sulphur in the cysteinatobis(ethylenediamine)cobalt(III) and bis(ethylenediamine)mercaptoacetatocobalt(III) ions using peroxodisulphate as oxidant. The effect of the acid-base equilibria of the reactants was established based on the dependences of the rate constant and the thermodynamic activation parameters ΔH and ΔS on perchloric acid concentration. The effect of ionic strength at various perchloric acid concentrations, was examined for the two complex ions. The combined effect of perchloric acid and sodium perchlorate was investigated in water-tert-butyl alcohol and water-ethylene glycol solutions. The transfer functions were calculated from the changes in the solubility of the reactants on passing from aqueous to the mixed aqueous-nonaqueous solutions, and the role of solvation during the oxidation of the complexes by peroxodisulphate was assessed based on the dependences of the transfer functions on the nonaqueous component content of the solvent system.