Studies On Synthesis, Characterization And Catalysis For Olefin Polymerization Of Novel Metallocene Catalysts

The metallocene catalysts, as homogeneous catalysts, have become the new generation catalysts for olefins polymerization after the Ziegler-Natta catalyst.Chromium-based catalysts played a significant role in coordination polymerization of olefins. The chromium catalytic systems have been largely ignored in the development of the homogeneous methylalumoxane (MAO)-activated systems that have attracted so much attention in the past decade. It is attributed to the difficulty of studying the chemistry of Cr(III) as a result of its paramagnetic nature. Recently, some of the most significant advances in Cp-based chromium catalyst systems have been made using precatalysts that bear an additional neutral donor, either bridged or unbridged to the Cp unit. Jolly et al. reported that half-sandwich type chromium complexes showed good activity for the polymerization of ethylene to give the polyethylene with narrow molecular weight distributions and high molecular weight. Ender et al. described cyclopentadienylchromium(III) complexes functionalized by quinoline or N, N-dimethylaniline for the polymerization of ethylene. These results revealed that nitrogen donor ligand-substituted cyclopentadienylchromium compounds could effectively catalyze the polymerizations of the olefins. However, the reports concerning oxygen donor ligand-substituted cyclopentadienyl chromium compounds are scarce. In chapter 2 we describe in detail the synthesis and properties of the oxygen donor ligand-substituted cyclopentadienyl chromium complexesη~5-1-(2-methoxyphenyl)-3, 4-diphenylcyclopentadienyl chromium dichloride dimmer andη~5-1-(2-methoxyphenyl)-2, 3, 4, 5-tetramethylcyclopentadienyl chromium dichloride dimer.