Synthesis, Structure And Catalytic Application Of Palladium(II) Complexes Bearing N-heterocyclic Silylenes

N-Heterocyclic silylene Si[N(tBu)CH]2 reacted with Pd of [(η3-C3H5)PdCl]2 in the molar ratio 1:1 in the solvent THF under -78℃to give a dark-red solution. Evaporated THF under vacuum, the brown powder was obtained. The 1H-NMR analysis of the product indicates that the complex was unstable. In solvent it decomposed quickly to give palladium. By using the palladium-(N-heterocyclic silylene) as the primary catalyst, styrene and aryl halide as reactants, sodium acetate as base, tetrabutyl ammonium bromide as phase transfer catalyst, N, N-dimethyl acetamide as solvent, the catalytic activity of palladium-(N-heterocyclic silylene) complex was studied. The effects of reaction temperature, reaction time, the amount of catalyst and different aryl halides were also studied. Using GC and GC-MS analysis discussed the catalytic behaviour of the palladium-(N-heterocyclic silylene) complex.The reason for the decomposing of palladium-(N-heterocyclic silylene) complexes may be that the condition of temperature which is difficult to control. N-heterocyclic silylene can be use as reduce reagent except for using as ligand, which may cause palladium complexes decompose, too. In the investigation of the catalysis of the complexes, different halogen atoms of the aryl halides have different catalytic activity. In all reactions, the catalytic activity of bromoacetophenone and styrene is the highest, the yield reaches 100%. Its reaction time is the shortest. The catalytic activity of 4-bromoanisole is lower than bromoacetophenone whose yield can reach 60.2%. The yield of 4-bromotoluene and 4-chloronitrobenzene can reach 47.4% and 38.06%, respectively. The 4-chloroacetophenone is not reacted with styrene. The results show that palladium-(N-heterocyclic silylene) complex has higher catalytic activity in the Heck reaction of aryl bromides with styrene using small amount of catalyst.