Synthesis, Characterization And Catalytic Performance Of Ferrocenylimine Molybdenum (VI) Complexes For Epoxidation

The epoxidation of olefins is one of the important methods for the synthesis of epoxides. The research of catalysts for olefin epoxidation, especial for asymmetric epoxidation, is a hotspot in chemistry at the present time.In this thesis, the dioxomolybdenum (â…¥) complexes of ferrocenylimine ligands used as novel catalyst for olefin epoxidation were studied in the following four aspects:1. A series of ferrocenyldiimine and ferrocenyliminoalcohol ligands were prepared by the condensation reaction of formylferrocene with aliphatic diamine or ethanolamine. Six novel dioxomolybdenum (â…¥) complexes of ferrocenylimine ligands were synthesized through the reaction of ferrocenylimine ligands with MoO₂Cl₂(THF)₂ at room temperature (Scheme 1 and Scheme 2). The structures of the complexes were characterized by elemental analysis, FT-IR, UV-Vis spectra, ¹H NMR. 2. The characters of the dioxomolybdenum (â…¥) complexes of ferrocenylimine ligands were investigated by electrochemical method and thermo analysis. The redox behavior of molybdenum (â…¥) ion and the stability of ferrocenyl group were influenced greatly by the coordination of ferrocenylimine ligands to molybdenum (â…¥) ion. The coordination ratio and stability constant of the complexes were determined by Molar Ratio method in THF.3. Using the dioxomolybdenum (â…¥) complexes of ferrocenylimine ligands as catalyst, the epoxidation of general olefins such as cyclohexene, 1 -hexene, styrene and 4-chlorostyrene with tert-butylhydroperoxide (TBHP) took place smoothly. The results indicated that these dioxomolybdenum (â…¥) complexes showed the good catalytic performance for olefin epoxidation. And the dioxomolybdenum (â…¥) complexes bearing ferrocenyldiimine ligands showed better catalytic activity for cyclohexene and 1 -hexene epoxidation than that for 4-chlorostyrene epoxidation. In addition, the dioxomolybdenum (â…¥) ferrocenyliminoethanolate complex showed better performance for aromatic olefin epoxidation than that for cyclohexene and 1 -hexene epoxidation.4. It was surprisingly discovered that the achiral dioxomolybdenum (â…¥) complexes bearing ferrocenylimine ligands showed certain asymmetric catalytic activity for the epoxidation of prochiral olefins. The dioxomolybdenum (â…¥) complex bearing N, N' -ferrocenylmethylenyl diamine can stereoselectively catalyze the epoxidation of styrene with 40% conversion at room temperature and a 53% e.e. of R-(-)-styrene oxide was obtained (Scheme 3). The reaction temperature and structures of the ligands influenced greatly on the asymmetric catalytic behavior of the complexes. The e.e. value decreased with the increase of reaction temperature. While the length of bridge chain changed in the ligands of the complexes, the stereo structure of the products obviously changed.Moreover, the reaction mechanism of olefin epoxidation was proposed based on the experimental results.