Study On The Group Ⅳ Metallocene And Late-transition Homogeneous Catalysts For Olefin Polymerization

In this dissertation, several series of metallocene catalysts were designed and synthesized, and their polymerization behaviors of a-olefins and polar monomers were also studied, which could be a basis for developing new types of catalysts for olefin polymerization.A new doubly bridged bis(cyclopentadienyl) dinuclear (μ-oxo)titanium complex was desiged to be synthesized by the reaction of the lithium compound of the doubly bridged bis(cyclopentadienyl) ligand with the (μ-oxo)semitetallocene titanium complex 1 ([CpTiCl2]2O). Treatment of the compound with concentrated HCl or HBr gave the corresponding Cp-decoordinated products, instead of the expected cis dinuclear metallocene complexes. All these titanium complexes were fully characterized. Their catalytic properties for ethylene and styrene polymerization were also studies in the presence of MAO. The results indicated that these complexes had similar activities for ethylene polymerization and the structures of catalysts had a little effect on catalystic activity but great effects on the properties of the polymers. Compound 1 showed a much higher activity towards styrene polymerization than the others, and the produced polymer is isotactic polystyrene. The influences of temperature, time, Al/Ti ratio were studied in details, which provided a good example for cooperative effects of bimetallic complexes.To extend the Diels-Alder reaction of benzyne with indenyl iron which reported by our group before the reactions of indenyl and fluorenyl ruthenium complexes with benzyne were studied and the corresponding monoadducts or bisadducts were obtained. Reaction of fluorenyl ruthenium compound with benzyne gave the monoadduct and a byproduct,9,9’-dipehenylfluorene. The possible mechanism of the formation of the byproduct was also studied. Typical complex was also tested for ring-opening metathesis polymerization (ROMP) in the presence of Grubbs’ second generation catalyst [(H2IMes)(PCy3)RuCl2=CHPh] but was found to be inactive under normal conditions. Bis(indenyl)iron as a neutral single-component catalyst methyl methacrylate (MMA) and styrene polymerization was found and the influence of temperature, solvent and cocatalysts were studied in details. A preliminary investigation of the mechanism of the polymerization was carried out. A radical mechanism was denied and a possible mechanism was propesed. In order to extent the application scope of the polymerization, research on the indenyl iron, indenyl nickel and fluorenyl rutheniym complexes were also conducted.