Ansa-Cyclohexyl-bis(4,5,6,7-tertrahydro-l-indenyl)zirconium dichloride(5)was used as catalyst for propylene and ethylene polymerization together with methyl aluminoxane(MAO)as the cocatalyst, Isotactic polypropylene(PP)was obtained with the highest activity of 6.37×10~7g PP(molZr)^(-1)h^(-1).The meso- meso(mmmmm)pentads sequence content of PP was determined by ^(13)C NMR spectroscopy.The dependence of the microstructure on the reaction temperature and the Al/Zr molar ratio was examined and the catalytic activity of complex 5 was compared with that of the similar ansa-zirconocene 3.The high activity of the new zirconocene 5 for propylene isospectic polymerization at high temperature(60℃)is the result of its unique bridged-group structure.Complex 5/MAO displays also high catalytic activity of 0.46×10~6 to 9.87×10~6g PE(molZr)^(-1)h^(-1) in the homo-polymerization of ethylene.The visometric molecular weight of PE ranges from 0.97×10~4 to 11.16×10~4 g·mol^(-1) under the given conditions.^(13)C NMR spectroscopy analysis proves the PE to be linear polyethylene(LPE).
The condensation of acetylacetone (CH3COCH2COCH3) with benzdine (H2N-C6H4-C6H4-NH2) yielded diimine ligand 1 HOC(Me)C(H)(Me)C=N(p-C6H4)(C6H4-p)N= C(Me)C(H)C(Me)OH),which was converted into sodium salts.And then the sodium salts reacted with monosalicylaldiminato titanium complex 2{3,5-di-But-2-(O)C6H2CHN(PH) TiCl3(THF)} in dried dichloromethane to give a new benzdine-bridged binuclear complex 3{3,5-di-But-2-(O)C6H2CHN(PH) 2 OC(Me)C(H)(Me)C=N(p-C6H4)-(C6H4-p)N=C(Me)C(H) C(Me) Ti2Cl4}.The complex 3 was charac-terized by 1HNMR and elemental analysis.In the presence of MAO(methylaluminoxane),the complex 3 in toluene was effective to catalyze polymerization,affording moderately high catalytic activity 1.93×105 g PE /(mol·Ti·h) and high molecular weight polyethylene 5.63×105 g/mol.The high temperature gel permeation chromatography (GPC) curve of polyethylene obtained revealed a single peak,but the molecular weight distribution (MWD=3.21) is obviously broader than that of the similar mononuclear titanium complex.The melting points of the obtained polyethylene reaches 138 ℃,indicating that the polyethylene is of high crystallinity.
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.
