Characterization and Reactivity of a Terminal Nickel(III)–Oxygen Adduct

AbstractHigh‐valent terminal metal–oxygen adducts are hypothesized to be the potent oxidizing reactants in late transition metal oxidation catalysis. In particular, examples of high‐valent terminal nickel–oxygen adducts are scarce, meaning there is a dearth in the understanding of such oxidants. A monoanionic NiII‐bicarbonate complex has been found to react in a 1:1 ratio with the one‐electron oxidant tris(4‐bromophenyl)ammoniumyl hexachloroantimonate, yielding a thermally unstable intermediate in high yield (ca. 95 %). Electronic absorption, electronic paramagnetic resonance, and X‐ray absorption spectroscopies and density functional theory calculations confirm its description as a low‐spin (S=1/2), square planar NiIII–oxygen adduct. This rare example of a high‐valent terminal nickel–oxygen complex performs oxidations of organic substrates, including 2,6‐di‐tert‐butylphenol and triphenylphosphine, which are indicative of hydrogen atom abstraction and oxygen atom transfer reactivity, respectively.