Oxidation of Some Transition-Metal Cyanide Compounds by Hydroxyl Radical

The oxidation of some transition-metal cyanide compounds by hydroxyl radical in aqueous media has been investigated by pulse radiolysis. For compounds of the type, M(CN) 6 4− where M is Fe, Ru, and Os, and for Mo(CN) 8 4− , the mechanism of their reaction with hydroxyl radical involves single electron transfer with the formation of the intensely colored metal complexes of the same stoichiometry as the starting materials. The u.v.-visible absorption spectra for these products for the iron, ruthenium, and osmium systems are reported along with the associated second order rate constants for their formation. The reaction of Mo(CN) 8 4− with hydroxyl radical has been studied by a competition technique using sodium bicarbonate. The values of the second order rate constants are near those expected of diffusion-controlled reactions and they range between ca. 5 × 10 9 to 1 × 10 10 M −1 s −1 .