Synthesis and characterization of dinuclear NHC–palladium complexes and their applications in the Hiyama reactions of aryltrialkyoxysilanes with aryl chlorides

Four linear dinuclear N-heterocyclic carbene (NHC)-palladium complexes {[PdCl(2)(NHC)](2)(μ-L)·xCH(2)Cl(2)} (1-4, L = pyrazine, DABCO) were synthesized through one-pot reactions of imidazolium salts, PdCl(2) and various bidentate N-heterocycles under mild conditions. The compounds were fully characterized by NMR, FT-IR and elemental analysis. Among them, complexes [PdCl(2)L(Mes)](2)(μ-pyrazine)·CH(2)Cl(2) (), [PdCl(2)L(iPr)](2)(μ-pyrazine) (1), and [PdCl(2)L(Mes)](2)(μ-DABCO) (2), were elucidated by single-crystal X-ray crystallography. Moreover, the catalytic activity of the NHC-palladium complexes was examined in the Hiyama reactions and the results showed that the dinuclear palladium complexes were the effective catalyst precursors for the reactions of aryltrialkyoxysilanes with aryl chlorides.