Kinetics and mechanisms of reduction of a sexidentate di(oxime–imine) complex of nickel(IV) with two-electron reductants, 1,2-di-hydroxybenzene and 1,4-dihydroxybenzene
Abstract
The kinetics and mechanisms of reduction of a nickel(IV) di(oxime–imine) complex, [NiIVL]2+(H2L = 3,14-dimethyl-4,7,10,13-tetra-azahexadeca-3,13-diene-2,15-dione dioxime), by 1,2-dihydroxybenzene (H2Z) and 1,4-dihydroxybenzene (H2Q) are reported. Both reactions proceed by consecutive one-electron transfers and kinetic traces are biphasic with quantitative formation of nickel(III) intermediates, [NiIIIL]+ and [NiIII(HL)]2+ depending on the pH. The dominant pathways for reduction of both nickel(IV) and nickel(III) involve the reductant anions HZ– and HQ–. Reactions of nickel(IV) are outer-sphere in nature while those of nickel(III) proceed by an inner-sphere pathway. Preliminary results on the oxidation of the corresponding nickel(II) complex by thallium(III) indicate that no detectable intermediate oxidation-state species is formed in this reaction.