Radical Capture at Nickel(II) Complexes: C–C, C–N, and C–O Bond Formation

Abstract

The dinuclear β-diketiminato NiII tert-butoxide {[Me3NN]Ni}2(μ-OtBu)2 (2), synthesized from [Me3NN]Ni(2,4-lutidine) (1) and di-tert-butylperoxide, is a versatile precursor for the synthesis of a series of NiII complexes [Me3NN]Ni–FG (FG = functional group) to illustrate C–C, C–N, and C–O bond formation at NiII via radical capture. {[Me3NN]Ni}2(μ-OtBu)2 reacts with nitromethane, alkyl and aryl amines, acetophenone, benzamide, ammonia, and phenols to deliver the corresponding mono- or dinuclear [Me3NN]Ni–FG species (FG = O2NCH2, R–NH, ArNH, PhC(O)NH, PhC(O)CH2, NH2, and OAr). Many of these NiII complexes are capable of capturing the benzylic radical PhCH(•)CH3 to deliver the corresponding PhCH(FG)CH3 products featuring C–C, C–N, or C–O bonds. Density functional theory studies shed light on the mechanism of these transformations and suggest two competing pathways that depend on the nature of the functional groups. These radical capture reactions at [NiII]–FG complexes outline key C–C, C–N, and C–O bond forming steps, foreshadowing families of nickel radical relay catalysts.