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

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.