Synthesis Of C₁ Symmetric Dimethylsilyl Bridged Bis ?Cyclopentadienyl? Ligands

Bridged metallocene catalysts are widely used in olefin polymerization.With the increasing industrial demands for new resins possessing desired properties,metallocene catalysts,especially silicon-bridged metallocene catalysts,have experienced rapid development in recent years because of their variable structure and excellent reaction performance.As one kind of the ligands attracting continus attentions,some C₁ Symmetric Silicon bridged cyclopentadienyl ligands have definitely different performances compared with their C₂ symmetry parteners?improved activities,excellent copolymerization performance and controlled sequence structure?.In the meanwhile,the synthesis of these C₁-symmetric Silicon-bridged cyclopentadienyl ligands needs more steps,thus the yields of some of these ligands are lower.This thesis mainly focuses on the processes optimization for the three C₁ symmetric dimethylsilicon bridged cyclopentadienyl ligands.Possible mechanisms for the major impurities were explored using LC-MS.Firstly,the two synthetic routes for ligand 1 were compared.It was found that the route of benzoindene dimethylchlorosilaneⁱndene[1,2b]-indole lithium salt was significantly better than that of the indene[1,2b]indole dimethylchloro-silane^benzoindene lithium salt ones.The isolated yield of ligand 1 increased from 40%to80%under optimized conditions?solvents,the amount of Me₂SiCl₂,the reaction time and bases et al?.Following optimized procedure,the isolated yield of ligand 2 was increased from30%to 58%.Up to 63%isolated yied could be achived with ligand 3.Hundred-gram scale?0.25mol?preparation of the ligand 1was performed in a 1L three-necked flask,104g?80%yield,96%purity?of target product was obtained without column purification.Similarly,ten-gram scale synthesis of ligands 2 and 3 were accomplished,48g?58%yield,95%purity?and 15g?63%yield,94%purity?of products were obtained respectively after column purification.One isomer of ligand 1 was characterized by single crystal diffraction.LC-MS analyses indicate that possible side reactions?hydrolysis,oxidation,and multi-site lithiation et al.?should be responsible for the impurities produced.Furthermore,the occurrence of un-anticipated lithization is closely related to the electron properties of the ligands employed.