Radical Capture at Ni(II) Complexes: C-C, C-N, and C-O Bond Formation

The dinuclear b-diketiminato Ni^IItert-butoxide {[Me₃NN]Ni}₂(μ-O^tBu)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 Ni^IIcomplexes [Me₃NN]Ni-FG to illustrate C-C, C-N, and C-O bond formation at Ni^II via radicals. {[Me₃NN]Ni}₂(μ-O^tBu)₂ reacts with nitromethane, alkyl and aryl amines, acetophenone, benzamide, ammonia and phenols to deliver corresponding mono- or dinuclear [Me₃NN]Ni-FG species (FG = O₂NCH₂, R-NH, ArNH, PhC(O)NH, PhC(O)CH₂, NH₂and OAr). Many of these Ni^II complexes are capable of capturing the benzylic radical PhCH(•)CH₃ to deliver corresponding PhCH(FG)CH₃ products featuring C-C, C-N or C-O bonds. DFT 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 [Ni^II]-FG complexes outline key C-C, C-N, and C-O bond forming steps and suggest new families of nickel radical relay catalysts.