Preperation Of Palladium Nanocatalyst And Its Catalytic Performance For Suzuki Cross-coupling Reaction

Palladium-catalyzed cross-coupling reaction has become one of the most powerful and convenient protocol for the construction of carbon-carbon bonds in agrochemistry, pharmaceutical chemistry, materials and synthetic chemistry. In this thesis, the water-soluble polymers PVP and silica materials were used as the support to prepare the Pd/diimine@SBA-15 and other supported nano-Pd catalysts, which were characterized by means of Fourier transform infrared (FTIR) spectroscopy, low-temperature nitrogen adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) etc. The catalytic performance of catalysts were investigated for Suzuki coupling reactions. The main results were obtained as follows:1. Palladium chloride has been loaded onto the PVP support to prepare the supported nano-Pd catalyst, and the effects of the valence state of Pd, molecular weight of PVP and the PVP amount on the catalytic performance. The results show that, the presence of bivalent Pd, low molecular weight PVP as the support and increase the amount of PVP can enhance the stability and catalytic activity of the Pd/PVP catalyst. Furthermore, a series of aryl bromides could react with phenylboronic acid in water solvent with the yield of 98%.2. Palladium chloride were loaded onto the diimine group modified SBA-15 to obtain the highly efficient and stable Pd catalyst (Pd/diimine@SBA-15). The research results show that, the Pd nanoparticles (3-5 nm) dispersed evenly on the support. When the catalyst including 0.05 mol% Pd was used, the coupling reactions of aryl bromides with benzene boric acid could occur effectively with the yield of 84-99%. For the coupling reactions of aryl chlorides with benzene boric acid, the catalyst including 1 mol% Pd was needed. After this catalyst was repeatedly used 4 times in the Suzuki coupling reaction, its catalytic activity was hardly reduced. The TEM testing showed that the Pd nanoparticles still remain highly dispersive without any gathering after being used four times.3. Pd/diimine@SiO2 was prepared by using diimine group modified amorphous silica. In the coupling reactions of aryl bromides with benzene boric acid over this catalyst with the amount of 0.05 mol% Pd,86-99% yield could be obtained. Compared with the Pd/diimine@SBA-15 catalyst, its catalytic activity was gradually reduced with an increase in the reuse times.4. NHC—palladium catalyst was also supported onto diimine@SBA-15 for Suzuki coupling reaction of aryl chlorides with benzene boric acid. After sulfonic group modified NHC ligands in the NHC-palladium catalyst, the stability of prepared NHC—Pd/diimine@SBA-15 could be improved.