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

The reaction of (NMe 4 ) 2 [Ni II (L Ph )(OAc)] (1[OAc], L Ph = 2,2',2''-nitrilo-tris-( N -phenylacetamide); OAc = acetate) with 3-chloroperoxybenzoic acid ( m -CPBA) resulted in the formation of a self-hydroxylated Ni III -phenolate complex, 2, where one of the phenyl groups of L Ph underwent hydroxylation. 2 was characterised by UV-Vis, EPR, and XAS spectroscopies and ESI-MS. 2 decayed to yield a previously characterised Ni II -phenolate complex, 3. We postulate that self-hydroxylation was mediated by a formally Ni IV O oxidant, formed from the reaction of 1[OAc] with m -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 m -CPBA. Addition of exogenous hydrocarbon substrates intercepted the self-hydroxylation process, producing hydroxylated products, providing further support for the formally Ni IV O entity. This study demonstrates that the reaction between Ni II salts and m -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 II / m -CPBA hydrocarbon oxidation catalysis.