Synthesis, Characterization And Catalytic Activity Of Polyamidoamine-salicylaldehyde Schiff Base Dendrimer Palladium Complex

Dendrimers are a class of three-dimensional, highly ordered, designed from molecular level polymer materials whose size, structure, molecular and functional groups are controlled. Polyamidoamine is the dendrimer which is researched most widely. The purposes of the research in this paper have three aspects. One is the synthesis and modification of PAMAM, the other is the preparation and characterization of palladium complex with polyamidoamine-salicylaldehyde schiff base (PAMAMSA) as support, and the final purpose is the rasearch on the catalytic performance of palladium complex in the Heck reaction. The main results are as follows:(1) The preparation and modification of 1.0-5.0G PAMAMThe 1.0-5.0G PAMAM have been synthesized successfully by divergent approach with the ethylenediamine as core. The half generation PAMAM were separated and purified by the method of colum chromatography with ethyl acetate and methanol as eluents. The peripheral units of integrated generation were modified by salicylaldehyde, then the 1.0-5.0G PAMAMSA were prepared. The structures of PAMAM and PAMAMSA are characterized by infrared spectrums, nuclear magnetism resonances.(2) The preparation of PAMAM-salicylidene schiff base palladium complexesA series of PAMAM-salicylidene schiff base palladium complexes were synthesized by the reaction of Schiff base with Li2PdCl4 in methanol. The structures of palladium complexes (PAMAMSA-Pd) were confirmed by the characterization of infrared spectrums, elemental analysis, thermogravimetric analysis and differential scanning caborimetry.(3) The catalytic performance of PAMAMSA-Pd in Heck reaction in organic solvent DMF The catalytic activity on Heck arylation reaction of iodobenzene or its derivatives with conjugated olefins was studied using 1.0-5.0G PAMAMSA-Pd as the catalyst precursor in DMF. The palladium complexes performed the efficient catalytic activity. The PAMAM-salicylidene Schiff base showed the good effects of supporting and dispersing the active centers, and the palladium complexes showed positive dendritic effect compared to PdCl2.The hightest yield can reach up to 94.4% in DMF and the TOF maximum can reach 75.45 (mmol product/mmol cat.·min). By being filtered and washed with solvent, 1.0G PAMAMSA-Pd can be recovered and reused. Although the catalytic activity is gradually reduced with the increase of the used times, the high yield of product still can be gotten by prolonging the reaction time for three times.(4) The catalytic performance of PAMAMSA-Pd in Heck reaction in waterThe catalytic activity on Heck arylation reaction of iodobenzene or its derivatives with conjugated olefins was studied using the 1.0-5.0G PAMAMSA-Pd as the catalyst precursor in water, with the phase transfer catalys tetrabutylammonium bromide exist. The palladium complexes could catalyze the Heck reaction efficiently, The PAMAM-salicylidene Schiff base showed the good effects of supporting and dispersing the active centers, and the palladium complexes showed positive dendritic effect compare to PdCl2. The yield can reach more than 67.1% in water and the TOF maximum can be up to 35.04 (mmol product/mmol cat.·min). By being filtered and washed with solvent, 1.0G PAMAMSA-Pd can be recovered and reused. Although the catalytic activity is gradually reduced with the increase of the used times, the high yield of product still can be gotten by prolonging the reaction time for three times.