C–H Functionalization Reactivity of a Nickel–Imide

We report bifunctional reactivity of the β-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(η2-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(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.