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.

本研究探究了三(三甲基膦)合二甲基镍(II)（NiMe₂(PMe₃)₃）与2,6-二氟芳基亚胺的反应。实验结果表明，成功合成了一系列双核镍配合物（5~8、11）。与此同时，当三(三甲基膦)合二甲基镍(II)分别与配体[2-甲基苯基-C(=NH)-2,6-二氟苯基]（9）和[2,6-二甲基苯基-C(=NH)-2,6-二氟苯基]（10）进行反应时，得到了两种意外的C-N偶联产物（12和13）。研究认为，该类偶联反应经历了N-H键与C-F键的活化过程。所合成的双核镍配合物在醛的硅氢化反应中展现出优异的催化活性。本研究通过计量反应对该反应的机理开展了系统探究，并通过原位¹H核磁共振波谱法检测到了双(η²-Si-H)合镍(II)中间体，该中间体可能是催化循环中的关键物种。