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 {[PdCl2(NHC)](2)(mu-L)center dot xCH(2)Cl(2)} (1-4, L = pyrazine, DABCO) were synthesized through one-pot reactions of imidazolium salts, PdCl2 and various bidentate N-heterocycles under mild conditions. The compounds were fully characterized by NMR, FT-IR and elemental analysis. Among them, complexes [PdCl2LMes](2)(mu-pyrazine)center dot CH2Cl2 (1), [PdCl2LiPr](2)(mu-pyrazine) (2), and [PdCl2LMes](2)(mu-DABCO) (3), 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.