Chitosan Imine Ring Palladium And Chitosan Schiff Base Palladium Catalyst Preparation, Characterization And Performance Study

In this thesis, the recent progress about the catalysts of Heck reaction and catalysis of chitosan metal complexes was reviewed in detail. On the basis, the chitosan-imine-palladacylce and chitosan-schiff base-PdCl₂ complexes were prepared and their catalytic performances in the Heck reaction were studied.1. Preparation and characterization of chitosan-imine-palladacycle complexesChitosan was modified with Phenyl aldehyde or its derivatives to obtain chitosan-schiff bases, and they were reacted with Li₂PdCl₄ in methanol to synthesize chitosan-imine-palladacycle complexes. Chitosan, chitosan-schiff bases and chitosan-imine-palladacycle complexes were characterized with IR, XRD, DTA-TG, fluorescence and XPS. According to the results of analysis, the structure of chitosan-imine-palladacycle complexes can be proposed.The structure of CS-imine-palladacycle complexes 1-102. Studies on catalytic performances of chitosan-imine-palladacycle complexes in Heck reaction(1) The coupling reaction of iodobenzene and acrylic acid catalyzed by Chitosan-imine-palladacycle complexes: The results show that chitosan-imine-palladacycle complexes have kept the activity of homogeneous catalyst. Comparing the TOF ofcatalysts, we can found that the activities are: 4>3>7>2>PdCl2>l>8>6>5>10>9. The yields of products catalyzed by 3,4, 7 are 91.9%, 96.0%, 93.0% separately. They even exceed the yield of 91.3% catalyzed by PdCb. Reusability of catalyst 3 in the reaction of iodobenzene and acrylic acid has been investigated. The results show that catalyst 3 could be reused four times after separating from the reaction mixture with the satisfactory catalytic activity.(2) The coupling reaction of iodobenzene and acrylamide catalyzed by Chitosan-imine-palladacycle complexes: Palladacycle complex 4 used as catalyst, the effect of reaction temperature and base on the reaction was studied. It was found that 120°C was the best temperature and BU3N was efficient base in the reaction. In the optimal conditions, the coupling reaction of iodobenzene and acrylamide were studied catalyzed by palladacycle complexes 1-10. The results show that complex 4 had the highest activity and the yield could reach 86.4%. The next was 10 and 7, and yields were 85.2% and 82.9%. The yields catalyzed by the other complexes were all about 75%. Reusability of catalyst 10 in the reaction of iodobenzene and acrylamide was studied. The results show that catalyst 10 could be reused five times after separating from the reaction mixture with the satisfactory catalytic activity.(3) The coupling reactions between derivatives of iodobenzene and acrylic acid or acrylamide catalyzed by palladacycle complex catalysts were studied. The results show that the catalysts had high activity to the iodobenzene coupling electron-withdrawing groups.(4) The coupling reaction of iodobenzene with acrylateI. Et3N as base, the effect of solvent on the reaction of iodobenzene with butyl acrylate was studied. It was found that only in p-xylene, catalysts didn't dissolve. P-xylene as solvent, the effect of base was studied. It was obtained that BU3N was the best base.II. In p-xylene and BU3N as base, the coupling reaction between iodobenzene and butyl acrylate catalyzed by palladacycle complexes 1-10 was studied. The yields of more than 90% were obtained except catalyzed by complexes 6 and 7. In this reaction, we studied the reusability of catalyst 1. The results show that catalyst 1could be reused five times.HI. In DMF and BU3N as base, we studied the coupling reaction of iodobenzene with acrylate catalyzed by the palladacycle complexes 1-10. The results show that dissolve of catalysts didn't happen and the yields all exceeded 95% in short time. In the reaction of iodobenzene and butyl acrylate, the reusabilities of catalysts 2, 7, 10 were investigated. The results show that the catalysts could reuse many times.IV. The coupling reaction of bromobenzene with acrylate catalyzed by catalysts 1-10 was studied. It was found that catalysts also had activity in the reaction. Especially palladacycle complex 7 used as catalyst, the yield of 79.6% can be obtained.3. Preparation and characterization of chitosan-schiff base-PdCl2 complex and study on the catalytic activities to Heck reaction catalyzed by the complex.(1) Chitosan-schiff base was synthesized by the reaction of chitosan and salicylaldehyde. Then it was reacted with PdCk to obtain chitosan-schiff base- PdC^ catalyst. The catalyst was characterized with IR, DTA-TG and XPS. According to the results of analysis, the structure of chitosan-schiff base-PdCb complex can be proposed.OH0.IV?" /PdCThe structure of the CS-schiff-base-PdCl2(2) We studied the effect of different reaction conditions (reaction temperature, amount of catalyst, different base and amount of bases, molar ratio of iodobenzene and acrylic acid, solvent) on the reaction of iodobenzene with acrylic acid and obtained the optimal conditions: lOmmol Phi, n (Phi): n (AA) as 1: 1.5, 27mmol Et3N, O.lg catalyst (Pd%: 2%), 6mL DMF, 70'C reacted for 7 hours. Under theoptimal conditions, the yield could reach 90.7%. By filtrated out and washed simplyfrom the reaction mixture, the catalyst could be reused five times without the loss ofactivity.(3) Comparing the catalytic performances of chitosan-schiff base-PdCh andchitosan- imine-palladacycle 7 in the reaction of iodobenzene with acrylate, we foundthat the activity of chitosan-imine-palladacycle is the better.