Reactivity of the bis[1-Hydroxy-2-(Salicylideneamino)Ethane]Manganese(II) complex toward hydrogen peroxide: Kinetics and intermediates of reaction

Kinetic studies of the oxidation of the bis1-hydroxy-2-(salicylideneamino)ethane]manganese(II) complex by hydrogen peroxide in acetonitrile solutions, at (30.0±0.2)°C, are described. A first-order dependence on the total manganese and the peroxide concentrations was verified, leading to the rapid formation of a Mn(III) intermediate, monitored by stopped-flow measurements, at 394 nm, with a rate constant k_f=(1.15±0.03)×10⁵ mol⁻¹ dm³ s⁻¹. The participation of hydroxyl radicals in the process was detected by spin-trapping EPR spectra. The final product was monitored both by EPR spectra, and spectrophotometrically by the slow decay of the intermediary Mn(III) species, with a rate constant k_d=(2.60±0.09) s⁻¹. It was identified as the corresponding mononuclear Mn(IV) complex, and characterized by different spectroscopic techniques. Comparative results of the reactivity of the starting complex versus molecular oxygen, leading to the same final product, were also discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 889–897, 1998