Structural Characterization and Oxidation Reactivity of a Nickel(II) Acylperoxo Complex

The nickel­(II)–acylperoxo complex [Ni­(TpCF3Me)­(κ2-mCPBA)] (1CF3Me) [TpCF3Me = hydrotris­(3-trifluoromethyl-5-methylpyrazolyl)­borate, mCPBA = m-chloroperbenzoate] was isolated and fully characterized. The electrophilic oxygenation ability of 1CF3Me toward sulfides and olefins was confirmed. The Michaelis–Menten-type behavior of thioanisole oxygenation indicates the existence of a pre-equilibrium of substrate association in the reaction. In addition, 1CF3Me retains H-atom abstraction ability for hydrocarbons with activated methylene C–H bonds (e.g., fluorene). The oxidations of styrenes and these readily oxidizable hydrocarbons follow second-order kinetics, first-order each with respect to 1CF3Me and substrate. The lack of clear acceleration in the decay of 1CF3Me in the presence of substrates with high C–H bond dissociation energies (e.g., cyclohexane) suggests that another reaction pathway contributes through the O–O-cleaved intermediate.