Journal of the American Chemical Society, Vol.134, No.24, 10114-10121, 2012
C-H Functionalization Reactivity of a Nickel-Imide
We report bifunctional reactivity of the beta-diketiminato Ni(III)-imide [Me3NN]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 [Me3NN]Ni-NHAd (2) for the resulting hydrocarbyl radical R. to give the nickel amide [Me3NN]Ni-N(CHMePh)Ad (3) (R-H = ethylbenzene) or aminoalkyl tautomer [Me3NN]Ni(eta(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 {[Me3NN]Ni}(2)(mu-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.