The Preparation Of An Anchored Heterogenized Salen Complex Catalyst For Aerobic Epoxidation Of Alkenes

In the thesis, heterogenized Salen-Mn (III) complex was prepared by the combination method of anchoring and sol-gel technique and their catalytic activities on epoxidation of alkenes were investigated.First, Salen-Mn (III) complex was obtained by the coordination of Mn(0Ac)2 with the ligand which was synthesized by the reaction of 3,5-di-tert-butyl-salicyaldehyde with 1,2-diaminocyclohexane. The catalyst and its precursor were characterized by FI-IR, 1H NMR respectively. The aerobic oxidation of styrene to its epoxide catalysted by Salen-Mn (III) complex was studied. The effects of the quantities of solvent, reaction temperature, reaction time, the molar ratios of isobutyradehyde and catalyst to substrate were obtained. It was found that the conversion of styrene can go up to 98.3% with a 85.9% selectivity of the epoxide, when the reaction was run at 35 ℃ for 8 hours with the molar ratios of 2.5 and 0.35% of isobutyradehyde and catalyst to the substrate, respectively. Furthermore, the catalyst was also applied to the epoxidation of different alkenes. And it was found that the conversion decreased in the order of a -methylstyrene, styrene, norbomylene, cyclohexene, 1-octene, 1-dodecene.Second, heterogenized Salen-Mn (III) complex was prepared by the combination method of anchoring and sol-gel technique. The catalyst was characterized by FI-IR, 1H NMR, XPS, ICP and N2 absorption.The relationship between catalytic property and internal structure was revealed. The factors affecting the properties of catalysts by the sol-gel method were investigated. It was found that the conversion of cyclohexene can go up to 99.7% with a 88.8% selectivity of the epoxide, when the catalyst was prepared at the optimal conditions. The heterogenized catalyst can be run for 6 times without obvious loss of activity. From the results of ICP and XPS analysis we can know that the catalyst has only 3% of Mn leaching mainly coming from the outer surface of the matrix. Therefore, the catalyst leaching problem of heterogenized catalyst was resolved partly, and the catalyst has better recyclable property. The comparison of heterogenized and homogenous catalyst on epoxidation of different alkene was also given.Third, chiral homogenous and heterogenized Salen-Mn (III) complexes were prepared by the methods mentioned above, and were applied as catalyst in alkene enantioselective epoxidation. It was found the enantioselectively decreased sharply after the chiral complex was immobilized in SiO2 matrix by the method mentioned above. But by increasing the amount of heterogenizedcatalyst b and prolonging reaction time in asymmetric epoxidation of 1,2-dihydronaphthalene, 54.2%e.e.was also obtained.