Iron catalysis of the reduction of oxime-bound nickel(IV) by hydroxylamine

Abstract

The nickel(IV) complex of the dianion of 2,6-diacetylpyridine dioxime was reduced very slowly by NH₃OH⁺ at pH 1–3, but this reduction is catalysed dramatically by dissolved iron, with Fe^II being the active reductant. With NH₃OH⁺ in excess, the products of the catalysed reaction are N₂ and Ni^II. Non-exponential kinetic profiles for this reaction are consistent with a sequence in which Fe^II is generated by le^– reduction of Fe^III by NH₂OH, after which Fe^II reduces Ni^IV to Ni^IIIvia competing protonated and non-protonated paths. Subsequent reduction of Ni^III is taken to be rapid. Rate constants and equilibrium quotients calculated from 15 runs are in accord with literature values.