Imine Nitrogen Bridged Binuclear Nickel Complexes via N–H Bond Activation: Synthesis, Characterization, Unexpected C,N-Coupling Reaction, and Their Catalytic Application in Hydrosilylation of Aldehydes

The
reactions of NiMe2(PMe3)3 with
2,6-difluoroarylimines were explored. As a result, a series of binuclear
nickel complexes (5–8, 11) were synthesized. Meanwhile, from the reactions of NiMe2(PMe3)3 with [2-CH3C6H4-C­(NH)-2,6-F2C6H3] (9) and [2,6-(CH3)2C6H3-C­(NH)-2,6-F2C6H3] (10), two unexpected C,N-coupling products (12 and 13) were obtained. It is believed that
these coupling reactions underwent activation of the N–H and
C–F bonds. The binuclear nickel complexes showed excellent
catalytic activity in the hydrosilylation of aldehydes. The mechanism
of the reaction was studied through stoichiometric reactions, and
the double-(η2-Si–H)–NiII intermediate was detected by in situ 1H NMR spectroscopy,
which may be the key point in the catalytic cycle.