Redox reaction of N,N′-phenylenebis-(salicylideneiminato)iron(III) with hypophosphorous acid in mixed aqueous medium

The kinetics of redox reaction between N,N′-phenylenebis-(salicylideneiminato)iron(III), hereafter referred to as [FeSalphen]+, and hypophosphorous acid was studied in mixed aqueous medium (DMSO:H2O; 1:4 v/v) under pseudo-first-order conditions at 26 ± 1 °C, µ = 0.2 C2 mol dm−3 (NaCl) and λmax = 435 nm. The reaction was found to be first-order in both reactants second-order overall, acid independent and displayed zero Bronsted–Debye salt effect. Evidence for the presence of free radicals was obtained during the course of the reaction, but none to support the formation of an intermediate complex. In general, the data obtained suggest an outer-sphere mechanism for the reaction. A plausible mechanism is proposed.