| Three types of half-metallocene complexes, in which the metal is coordinated with a cyclopentadienyl and a non-cyclopentadienyl ligands, have been designed and synthesized with the formula LCpTiCl~. L is a non-cyclopentadienyl containing oxygen or mtrogen atoms. When L was biphenols( [0,0]), 8-hydroxy-quinolines( [0,N]), or azoles(Np) separately, the half-metallocene complexes were [0,0]CpTiC1 , [0,N]CpTiC12, or NpCpTiCI2 correspondingly. The catalytic properties of these complexes for ethylene polymerization with activation by Methylalumoxane(MAO) and the structural characters of polyethylene obtained were studied.Three kinds of [0,0]CpTiC1 had been synthesized when [0,0] was catechol(C6H602), 2,2' -biphenol(C 12H8Oj, or 2,2' -binaphthol(C2J-11202), respectively, in the case of [0,N]CpTiC12, [0,N] was 8-hydroxyl-quinoline(C9H7NO),2-methyl-8-hydroxyl-quinoline(C1 0H.9N0), and 8-hydroxyl-5 -nitro-quinoline(C9H6N2 03), respectively. There were five kinds of NpCpTiC12, in which Np was pyrolyl(Pr: C4H4N), indolyl(Id:C8H6N); 7-azoindolyl(Ai:C7H5N2), indazolyl(Iz: C7H5N2), and benzimidazolyl(Bi: C7H5N2) respectively. All of them were prepared by the reactions of CpTiCI3 with the anions of the relevant ligands, and characterized by elemental analysis, IR, or NMIR.It was proved that all the LCpTiCl~ was active for ethylene polymerization at 30 0C and 0.1 MPa with activation by MAO, and exhibited much higher activity than CpTiC13. For the LCpTiCl~/MAO system, the catalytic activity followed an "up and down" profile withincrease in the Al/Ti molar ratio, and reached a maximum value when the Al/Ti molar ratio was about 500 which was much lower than that of metallocene system.The results showed that the activity of the (C6H402)CpTiC1JMAO system decreased successively with increase of the aromatic rings in the following order: (C6H402)>(C12H8Oj>(C20H12Oj, and that the polyethylene was characteristic of bi-model distribution with a molecular weight of M~ l2.5x 10~ and a molecular weight distribution of M,JM~ 7.42, or of narrow distribution with M~ of 52.Ox 10~ and M./M~ of 2-3, depending on the synthetic methods of [O,O]CpTiCl. For the [O,N]CpTIC12/MAO system, the activity increased markedly when there was an electron-donor substituent next to N , such as a methyl(2.8 X 1 O5gPE/molTi o h), and decreased significantly when there was an electron-acceptor substituent , such as nitro in the benzene ring; also the active decreased when the polymerization time was too long, and increased when there was a proper pre-reaction time; the polyethylene obtained was characteristic of narrow molecular distribution(MjM~2'-2.8) with MM. of 40x iO~. Besids, the polyethylene obtained by the NpCpTiCL2/MAO system had the same structural properties with MJM~ less than 3 and M.,~, of 35x i0~.Based on the Amsterdan Dense Function(ADF) by Computer Molecular Simulation, the theoretical investigations of reactions between [C101-19N0]CpTiC12 and ALMe3, or different cocatalytic site models of MAO allowed us to reach some significant insights into the mechanismsinvolved in the formation of active species responsible for ethylene polymerization. The energy required to form the [C10H9NO]CpTiCH3~ cation from dissociation of [C10H9N0]CpTiCH3C1 A1Me3 and different kinds of chlorine-bridged and oxygen-bridged [C10H9N0]CpTiCH3C1 MAO model adducts accounted for the higher cocatalytic activity exhibited by MAO with respect to A1Me3. Both the presence of highly acidic aluminum atoms and negative charge dispersion power of XMIAO macroanions (X=Cl,Me) were essential features in determining low dissociation energies. The stabilization of halfmetallocene cations performed by ethylene coordination to titanium, and the A1Me3 content in MAO played an important role in ion-pair separation for affecting active species formation, both protecting the acidic cocatalytic sites as well as affecting the formation of stabilized [C101-{9N0]CpTiCH3--O adducts. Besides, The presence of moderately coordinating oxygen atoms in ~vIAO...
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