Kinetics of the [Mn(CN) 6] 4− + e − ⇌ [Mn(CN) 6] 5− reaction at mercury electrodes

Abstract

The kinetics of the [Mn(CN) 6] 4− + e − ⇌ [Mn(CN) 6] 5− system at mercury electrodes has been investigated using cyclic voltammetry, chronocoulometric and faradaic impedance methods. The standard heterogeneous rate constant k s of this process in 1 mol dm −3 NaCN is 0.26 ± 0.01 5 cm s −1 and the cathodic transfer coefficient α is 0.59 ± 0.01, similar to the kinetic characteristics of the [Cr(CN) 6] 3− /[Cr(CN) 6] 4− system. The diffusion coefficient of [Mn(CN) 6] 4− in 1 mol dm −3 NaCN is (5.6 ± 0.8) × 10 −6 cm 2 s −1. The role of the composition of the inner coordination sphere of manganese complexes in their electroreduction mechanism and the possibility of the further electroreduction process [Mn(CN) 6] 5− + e − → [Mn(CN) 6] 6− at mercury electrodes are discussed using literature data.