Newer manifestations of reactivity of coordinated peroxide at metal and non-metal centres

Abstract

Newer reactions of coordinated peroxide at metal and non-metal centres are described. Reactions of peroxo-metal complexes with SO2(g), NO2(g), and CO2(g) have been carried out in aqueous medium. Typically, reactions of a highly peroxygenated metal complex, A[V(O2)3]·3H2O (A=Na,K), follow an unprecedented sequence. The deep blue ESR-silent solution of A[V(O2)3]·3H2O reacts to produce a yellow, ESR-inactive solution that on further reaction with the chosen substrate affords a green-blue ESR-active (cf. VO2+) solution. The reaction proceeds through distinct steps such that, first, one of the coordinated peroxides undergoes a two-electron irreversible cleavage of the O-O bond leading to a diperoxy-mono(sulphato)vanadate(V) intermediate, [(O2)2V-O-SO3]−, that readily undergoes hydrolysis to produce H2SO4 and an aquaoxo-diperoxovanadate(V) complex, [VO(O2)2H2O]−. The latter complex reacts with more SO2(g) causing reduction of vanadium (V) to vanadium (IV) and conversion of coordinated peroxide to coordinated sulphate producing the bis(sulphato)vanadyl complex, [VO(SO2)2(H2O)2]2−.