Synthesis, Structure And Polymerization Behaviors Of Constrained Geometry Double Silylene-Bridged Metallocene Complexes

Thirteen double-bridged binuclear titanium (zirconium) complexes were synthesized, including seven double-bridged binuclear zirconium complexes, five asymmetric double-bridged binuclear metallocene complexes and one double-bridged mono-nuclear titanium complex. They molecular were all well characterized by 1H NMR, MS, I.R. and E.A.. The structure of complex 3 was confirmed by X-ray diffraction.Eight double-bridged binuclear complexes were obtained from the reaction of [μ,μ-(SiMe2)2 (C5H3)2]Li2 and RCpMCl3 (M=Ti, Zr; R=H, alkyl, benzyl, MeOEt etc) in THF. They were homo binuclear complexes and the two metals in the molecular structure possess symmetric coordination environment.Five asymmetric double-bridged binuclear metallocene complexes were synthesized by the reaction of lithium salts of asymmetrical ligand and RCpMCl3 (M=Ti, Zr; R=H, alkyl, allyl, etc). When activated with MAO, these complexes are highly active catalysts for ethylene polymerization.All these complexes were used to catalyze the polymerization of ethylene in the presence of MAO. The results were summaried as follows:(1) The activities of the binuclear catalytic systems are close to or higher than that of Cp2ZrCl2 especially under low molar ratio of Al/M. The maximal activity reaches to 106 g PE/(mol-Zr·h).(2) The molecular weight of the polymer generated from the binuclear catalytic system is higher than that obtained from Cp2ZrCl2 .(3) The effect of Al/M molar ratio, polymerization time, temperature, concentration of catalyst and ethylene pressure on polymerization was studied. The activities were improved with the increasing of Al / M molar ratio. The optimum conditions of time, temperature and concentration have been obtained.(4) The copolymerization of ethylene/1-hexene with these complexes was also studied, and the result indicated that these complexes were highly activity and co-polymer with broad MWD was gained. Five double-bridged binuclear titanium complexes were used as catalyst in the presence of methylaluminoxane (MAO) for ethylene polymerization. The result was similar to zirconium system except that the activity was less than that of zirconium system.In addition, some trail works were also processed in this paper.When activated with MAO,theμ-arylimido binuclear titanium complexes show high activity for ethylene polymerization [maximum Act = 3.420×105 g-PE/(mol-Ti·h)]. The obtained PE has high molecular weight (maximum Mw = 6.59×105 g/mol) and broad molecular weight distribution (MWD = 5.88). The substitutent on the cyclopentadienyl ligand has great impact on the activity of these complexes. The optimum polymerization activity are obtained at T = 60℃and t = 1.0 h...