Mechanism of Thiosulphate Oxidation by Di-μ-Oxo-Tetrakis (2, 2’- bipyridine) – Dimanganese (III, IV) Perchlorate in Acidic Medium
O.A. Babatunde 1 and Patricia Ese Umoru2
Department of Chemistry,
Nigerian Defence Academy, Kaduna, Nigeria
Email: patriciaumoru@yahoo.com
Abstract: The mechanism of the oxidation of di-μ-oxo-tetrakis(2,2’ – bipyridine)-dimanganese (III,IV) perchlorate (herein referred to as [(bipy)2 MnIIIO2MnIV(bipy)2]3+ with S2O32- was studied at constant concentration of [(bipy)2 MnIIIO2MnIV(bipy)2]3+ at 6 x 10-4 mol dm-3, ionic strength of 0.5 mol dm-3, [H+] = 1 x 10-3 mol dm–3 and λmax = 683 nm. The stoichiometry of 1: 3 was observed for the system. The order of reaction is first order in the oxidant and reductant, giving an overall second order rate constant. Acid dependence rate constant on oxidant were positive for the system. The acid dependent rate equation is given as: kH+ = (a + b [H+])[(bipy)2 MnIIIO2MnIV(bipy)2][S2O32-]. Negative salt effect was observed for the system. The results of spectroscopic and kinetic investigation did not indicate intermediate complex formation in the course of the reaction and acrylamide addition did not indicate gel formation. Based on the results obtained, a plausible mechanism for the reaction has been proposed in line with Proton Coupled Electron Transfer (PCET) reaction pathways.
Keywords: Mechainsm, Thiosulphate Ion, Di-μ-Oxo-Tetrakis (2,2’- bipyridine)-Dimanganese (III,IV) Perchlorate.