Electron-transfer reactions and the self-exchange rate of the perruthenate(VII)–ruthenate(VI) couple

Abstract

The kinetics of the reduction of perruthenate(VII) by [Fe(CN)₆]^4– and [W(CN)₈]^4– and the oxidation of ruthenate(VI) by [Mo(CN)₈]^3– and [Ru(CN)₆]^3– have been studied in aqueous alkaline solutions using stopped-flow techniques. The cross-reaction data have been treated according to the Marcus relations and yield a self-exchange rate constant of 10 ± 5 dm³ mol^–1 s^–1(25.0 °C, I= 1.0 mol dm^–3) for the perruthenate(VII)–ruthenate(VI) couple. This rather slow self-exchange rate is discussed in terms of possible structural differences between perruthenate(VII) and ruthenate(VI) in alkaline solution.