Electron Transfer Reactions of Tetrakis (2, 2- Bipyridine)-µ Oxodiiron(III) Complex and Dithionate Ion in Aqueous Acidic Media: Kinetic and Mechanistic Approach

Abstract

Electron transfer reaction of tetrakis(2,2’- bipyridine)-µ-oxodiiron(III) complex (Fe₂O⁴⁺) and  dithionate  (S₂O₆^2- )  has been carried out in aqueous hydrochloric acid. The reaction was carried out at [H⁺] = 1.0  × 10^-3  mol dm^-3, I = .3.0 × 10^-1   mol dm^-3(NaCl), T= 26 ± 1°C, and  λ_max = 520nm. The stoichiometric ratio of the reaction is 1:1.The reaction is first order with respect to [Fe₂O⁴⁺] and zero-order on [S₂O₆^2-] and is not hydrogen ion and ionic strength dependent. Added anions and cations do not affect the reaction, there was no gel formation upon the addition of acrylamide and excess methanol to the reaction mixture, which shows the absence of polymerisation, The products of the reaction were identified as Fe²⁺ and SO₄^2-.  With recourse to empirical data, the reaction is rationalised to occur via an outer sphere pathway with ion pair character. A Plausible mechanism has been proposed for the reaction.