Synthesis And Catalytic Properties Of Dinuclear C₁-ansa-titanocenes

Two cyclopentadiendienyls of dinuclear C1-ansa-titanocenes catalysts are connected by a carbon bridged foundation. The introduction of the foundation makes two cyclopentadiendienyls not rotated metal-cyclopentadiendienyl for axis, twists two cyclopentadiendienyls to form sandwich structure, increases molecular rigidity and the dihedral angle, and then enlarges the reaction space, affects the activity of metal center. Therefore, the catalytic activity and stereo selective can be adjusted by changing the structure of the groups of bridge foundation. Besides, dinuclear C1-ansa-titanocenes molecular has two metal centers and micro chemical environment changing between metal centers, which are benefit to the formation of many activity centers. The main object of this paper is the synthesis of some different bridged dinuclear C1-ansa- titanocenes and the study of the effect of the bridge-chain structure on the catalytic properties.(1) Nine dinuclear C1-ansa-titanocenes compounds have been synthesized [[R1R2C-(C5H4)(C5H3)TiC12]2X [X=(CH2CH2)2O; (CH2)2C6H4; (CH2C6H4)2; R1=R2=CH3, (CH2)4, (CH2)5].(2) When 3-oxa-pentamethylene bridged dinuclear C1-ansa-titanocenes{[(CH2)5C] (C5H3)(C5H4)TiCl2}(CH2CH2)2O and 4,4'-bis(methylene)biphenylene bridged dinuclear C1-ansa-titanocenes{[C(CH2)5](C5H3)(C5H4)TiCl2}(XH2C6H4)2 have respec-tively tested for methyl methacrylate (MMA) bulk polymerization in combination with cocatalyst of methylaluminoxane (MAO), the results of polymerization showed that the conversion of MMA were up to 96.11% and 90.08%, the viscosity average molecular weight of PMMA were 7.31X105 and 5.55X105, The molecular weight distributions (MWD) of PMMA were 4.66 and 5.24, the syndiotacticity of PMMA were up to 78.6% and 81.3%. Their catalytic activity, molecular weight, molecular weight distribution, syndiotacticity and so on are better than the corresponding mononuclear titanocene catalyst.(3) The results of polymerization showed that their catalytic activity, molecular weight, molecular weight distribution and so on played an outstanding performance when eight dinuclear C1-ansa-titanocenes compounds have been tested as catalysts for ethylene polymerization. The molecular weight distributions (MWD) of PMMA were from 2.25 to 5.24. The order of the catalytic activity from high to low was phenylenedimethylene bridged dinuclear C1-ansa-titanocenes,3-oxa-pentamethylene bridged dinuclear C1-ansa-titanocenes,4,4'-bis(methylene)- biphenylene bridged dinuclear C1-ansa-titanocenes. In the same kind of dinuclear C1-ansa-titanocenes, the catalytic activity of isopropyl bridged titanocene was greater than that of cyclopentyl bridged titanocene which was greater than that of cyclohexyl bridged titanocene.4) The molecular weight distributions of the flexible bridged dinuclear C1-ansa-titanocenes were slightly wider than the rigid bridged dinuclear C1-ansa-titanocenes in ethylene polymerization.