Oxaziridine cleavage with a low-valent nickel complex: Competing C-O and C-N fragmentation from oxazanickela(II)cyclobutanes

Reacting the low-valent nickel complex [(dtbpe)Ni]₂(μ-η²:η²-C₆H₆) with oxaziridines was found to form mixtures of imine, amide and aldehyde products. If the N-substituent of the oxaziridine is sufficiently bulky, a short-lived intermediate can be isolated and characterized by X-ray diffraction studies as an oxazanickela(ii)cyclobutane. This is the first well-defined example of N-O oxidative addition of an oxaziridine to a transition metal. Subsequent fragmentation of this oxazanickelacyclobutane forms a complex mixture of products, including a nickel(ii) imido complex, demonstrating that oxaziridines can serve as nitrene precursors. Preliminary mechanistic analysis is consistent with a bimetallic mechanism of fragmentation of the oxazanickelacyclobutane to form the nickel imido and η²-aldehyde complexes.