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

Abstract

Four linear dinuclear N-heterocyclic carbene (NHC)–palladium complexes {[PdCl₂(NHC)]₂(μ-L)·xCH₂Cl₂} (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 [PdCl₂L^Mes]₂(μ-pyrazine)·CH₂Cl₂ (1), [PdCl₂L^iPr]₂(μ-pyrazine) (2), and [PdCl₂L^Mes]₂(μ-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.