ABSTRACT:Three new titanium complexes bearing salicylidenimine ligands-bis[(salicylidene)-2,3,5,6-tetrafluoroanilinato]titanium(IV) dichloride (1), bis[(3,5-di-tertbutylsalicylidene)-2,3,5,6-tetrafluoroanilinato]titanium(IV) dichloride (2), and bis[(3,5-di-tert-butylsalicylidene)-4-trifluoromethyl-2,3,5,6-tetrafluoroanilinato]titanium(IV) dichloride (3)-were synthesized. The catalytic activities of 1-3 for ethylene polymerization were studied with poly-(methylaluminoxane) (MAO) as a cocatalyst. Complex 1 was inactive in ethylene polymerization. Complex 2 at a molar ratio of cocatalyst to pre catalyst of Al MAO /Ti ϭ 400 -1600 showed very high activity in ethylene polymerization comparable to that of the most efficient metallocene complexes and titanium compounds with phenoxy imine and indolide imine chelating ligands. It gave linear high-molecularweight polyethylene [weight-average molecular weight (M w ) Ն 1,700,000. weight-average molecular weight/ number-average molecular weight (M w /M n ) ϭ 4 -5] with a melting point of 142°C. The ability of the 2/MAO system to copolymerize ethylene with hexene-1 in toluene was analyzed. No measurable incorporation of the comonomer was observed at 1:1 and 2:1 hexene-1/ethylene molar ratios. However, the addition of hexene-1 had a considerable stabilizing effect on the ethylene consumption rate and lowered the melting point of the resultant polymer to 132°C. The 2/MAO system exhibited low activity for propylene polymerization in a medium of the liquid monomer. The polymer that formed was high-molecular-weight atactic polypropylene (M w ϳ 870,000, M w /M n ϭ 9 -10) showing elastomeric behavior. The activity of 3/MAO in ethylene polymerization was approximately 70 times lower than that of the 2/MAO system.
New dinuclear titanium(IV) dichloride complex with the chelating bis 4,4´ bis imine (3,5 di tert butylsalicylidene)octafluorobiphenyl ligand was synthesized. In the presence of polymethylaluminoxane (MAO), the complex showed high catalytic activity in ethylene poly merization leading to high molecular (M n ∼2500000) linear polyethylene with a high polydis persity index (M w /M n ∼7.0) and high melting point (142 °С). The catalytic activity in propylene polymerization in a medium of liquid monomer is substantially lower, and the polypropylene formed is a high molecular atactic elastomer.
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