Redox chemistry of [Fe2(CN)10]4–. Part 2. Reaction with thiosulfate

Abstract

The oxidation of thiosulfate by the iron(III) dimeric complex [Fe₂(CN)₁₀]^4– in acidic aqueous solution at an ionic strength of 1.0 mol dm^–3(Na₂SO₄) has been investigated by stopped-flow and conventional spectrophotometry. The overall reaction is quite complicated, occurring in two distinct processes. The first comprises two steps, involving an intermediate, and results in a relatively fast one-electron reduction to [Fe₂(CN)₁₀]^5–, the rate of which was monitored by the stopped-flow technique; this is followed by a much slower second reaction leading to fission of the cyanide bridges and the formation of the pentacyano(thiosulfato)ferrate-(II) and -(III) complexes. Separate mechanisms are given for each step based on the observed kinetic data.