Novel titanium (IV) diolate complexes with thiophene-containing OSO-type ligand as pre-catalyst for ethylene polymerization and ethylene - propylene copolymerization

Abstract

New titanium (IV) complexes with diolate ligand containing additional donor sulfur atom have been synthesized and characterized. Structure of complex 2 was established by X-ray diffraction. Titanium atom adopts a distorted tetrahedral geometry formed by oxygen atoms of two ligands and isopropoxy-groups. Activation of these complexes with {EtnAlCl3-n + Bu2Mg} led to a highly active catalytic system for ethylene polymerization with an activity up to 2 tons PE·molTi-1·atm-1·h-1. Linear ultrahigh molecular weight polyethylenes (1.9-5.7 106 Da) were obtained under these conditions. The obtained polyethylenes are suitable for the modern methods of polymer processing - the solventless solid state formation of super high-strength (breaking strength up to 2.6 GPa) and high-modulus (elastic modulus up to 164 GPa) oriented films and film tapes. The precatalysts 1-3 were also active in ethylene-propylene copolymerization producing copolymers with a content of propylene units in the range 28-33%. The influence of the nature of the «leaving» monodentate σ-ligands (Cl, OiPr and N(CH3)2) and the organoaluminum co-catalyst (Et2AlCl and Et3Al2Cl3) on the activity of catalytic systems and the properties of the resulting polymers were studied.