Aromatic and aliphatic hydrocarbon hydroxylation a formally NiO oxidant.

The reaction of (NMe)[Ni(L)(OAc)] (1[OAc], L = 2,2',2''-nitrilo-tris-(-phenylacetamide); OAc = acetate) with 3-chloroperoxybenzoic acid (-CPBA) resulted in the formation of a self-hydroxylated Ni-phenolate complex, 2, where one of the phenyl groups of L underwent hydroxylation. 2 was characterised by UV-Vis, EPR, and XAS spectroscopies and ESI-MS. 2 decayed to yield a previously characterised Ni-phenolate complex, 3. We postulate that self-hydroxylation was mediated by a formally NiO oxidant, formed from the reaction of 1[OAc] with -CPBA, which undergoes electrophilic aromatic substitution to yield 2. This is supported by an analysis of the kinetic and thermodynamic properties of the reaction of 1[OAc] with -CPBA. Addition of exogenous hydrocarbon substrates intercepted the self-hydroxylation process, producing hydroxylated products, providing further support for the formally NiO entity. This study demonstrates that the reaction between Ni salts and -CPBA can lead to potent metal-based oxidants, in contrast to recent studies demonstrating carboxyl radical is a radical free-chain reaction initiator in Ni/-CPBA hydrocarbon oxidation catalysis.