C–H Functionalization Reactivity of a Nickel–Imide

Abstract

We report bifunctional reactivity of the β-diketiminato Ni(III)-imide [Me(3)NN]Ni═NAd (1), which undergoes H-atom abstraction (HAA) reactions with benzylic substrates R-H (indane, ethylbenzene, toluene). Nickel-imide 1 competes with the nickel-amide HAA product [Me(3)NN]Ni-NHAd (2) for the resulting hydrocarbyl radical R(•) to give the nickel-amide [Me(3)NN]Ni-N(CHMePh)Ad (3) (R-H = ethylbenzene) or aminoalkyl tautomer [Me(3)NN]Ni(η(2)-CH(Ph)NHAd) (4) (R-H = toluene). A significant amount of functionalized amine R-NHAd is observed in the reaction of 1 with indane along with the dinickel imide {[Me(3)NN]Ni}(2)(μ-NAd) (5). Kinetic and DFT analyses point to rate-limiting HAA from R-H by 1 to give R(•), which may add to either imide 1 or amide 2, each featuring significant N-based radical character. Thus, these studies illustrate a fundamental competition possible in C-H amination systems that proceed via a HAA/radical rebound mechanism.