Synthesis, structure and catalytic activity of dicarbene dipalladium complexes with different substituents

A series of ethylene bridged di-NHC dipalladium complexes (1–5) with different substituents on N of imidazolydene were prepared. The influence of the different substituents on the structure and catalytic reactivity of the complexes were studied. The molecular structures of 3 and 4 were determined by X-ray diffraction studies. The structures of complexes consist of two perpendicular pseudo-square-planar subunits in a cis configuration. The catalytic activity of the new binuclear palladium complexes was successfully tested in the Mizoroki–Heck reaction. The complexes with aryl substituent have better activity than that with alkyl substituent, meanwhile, the different substituents on phenyl group have a little effect on both regioselectivity and the yield of the product as well.