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

Abstract

The nickel(II)-acylperoxo complex [Ni(Tp(CF3Me))(κ(2)-mCPBA)] (1(CF3Me)) [Tp(CF3Me) = hydrotris(3-trifluoromethyl-5-methylpyrazolyl)borate, mCPBA = m-chloroperbenzoate] was isolated and fully characterized. The electrophilic oxygenation ability of 1(CF3Me) 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, 1(CF3Me) 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 1(CF3Me) and substrate. The lack of clear acceleration in the decay of 1(CF3Me) 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.