By treating disodium(thiophenedirnethylene)dicyclopentadienide C_4H_2S(CH_2C_5H_4Na)_2 with two equivalent of CpTiCl_3 or CpZrCl_3 DME at 0℃ in THF,two new thiophenedimethylene bridged binuclear metallocenes [Cl_2MC_5H_5][C_5H_4CH_2C_4H_2SCH_2C_5H_4][C_5H_5MCl_2](M=Ti 3,M=Zr 4)were synthesized in high yield and their structures were characterized by ~1H-NMR.These complexes were used as catalysts for ethylene polymerization in the presence of methylaluminoxane(MAO).The effects of polymerization temperature,time,concentration of catalyst,molar ratio of MAO/Cat on polymerization were studied in detail.The catalytic activities of thiophenedimethylene bridged binuclear metallocene catalysts(3,4)reached 2.44×10~5 g PE mol^(-1)·cat^(-1)·h^(-1),9.61×10~5 g PE mol^(-1)·cat^(-1)·h^(-1) respectively,which are higher than that of pheneyldimethylene bridged binuclear metallocene catalysts and much higher than that of corresponding mononuclear metallocenes(Cp_2TiCl_2 and Cp_2ZrCl_2).The molecular weight distribution curves of polyethylenes produced by binuclear metallocene catalysts(3,4)and by mononuclear metallocene catalyst have only single peak,but the former(MWD=3.5-4.7)is obviously broader than the latter(MWD=2.0-2.2).
Mononuclear carbon bridged cyclopentadienyl chromium complexes of the type [（C5H4）C（C5H 10）CH2（C5H4N）]CrCl2 （1）, [（C5H4）C（CH3）2CH2（C5H4N）]CrCl2 （2） and homodinuclear chromium complex of the type （CH3）2C{[（C5H3）C（CH3）2CH2（C5H4N）]CrCl2}2 （3） were prepared by treatment of the lithium salts of cyclopentadiene ligands with pyridyl group with CrCl3（THF）3 in THF solution. All complexes were structurally characterized by mass spectra and elemental analysis. The structure of complex 1 was determined by X-ray diffraction analysis. Activated by MAO, complexes 1 and 2 are efficient catalysts in the polymerization of ethylene yielding polyethylene （PE） with a high molecular weight （MV ranging from 225800 to 637800 g·mol -1, 30 ≤Tp≤70℃ under 0.9 MPa monomer pressure ）. High activities of polymerization are related to the unique electronic and steric structure of complexes 1 and 2 .The melting points of the polymers determined by DSC and characterization data of 13C NMR all show the synthesis of linear polyethylene （LPE） with a low branching extent.
