Phenylene-Bridged OSSO-Type Titanium Complexes in the Polymerization of Ethylene and Propylene.

The dichloro titanium complexes (OSSO )TiCl () and (OSSO)TiCl () bearing -phenylene-bridged OSSO-type ligands [OSSO -H = 6,6'-((1,2-phenylenebis(sulfanediyl))bis(methylene))bis(2,4-di--butyphenol) and OSSO-H = 6,6'-((1,2-phenylenebis(sulfanediyl))bis(methylene))bis(2,4-bis(2-phenylpropan-2-yl)phenol)] were prepared and characterized. The X-ray structure of revealed that Ti atom has an octahedral coordination geometry with an - wrapping of the [OSSO] ligand. In solution at 25 °C, mainly retains the symmetric structure, whereas shows an equilibrium between - and -symmetric stereoisomers. Activation of with (PhC)[B(CF)] led to a highly active catalytic system with an activity of 238 kg·mol ·bar·h; linear polyethylene with a of 122 °C and of 107 kDa were obtained under these conditions. Catalyst displayed the moderate activity of 59 kg·mol ·bar·h. Gel permeation chromatography analysis revealed the formation of high-molecular-weight polyethylenes with very large distributions of the molecular weights, indicating a low control of the polymerization process, probably becaue of the presence of different active species in solution. Density functional theory investigation provides a rational for the relative high-molecular-weight polymers obtained with these complexes. The precatalyst was also active in propylene polymerization producing atactic oligomers terminated with unsaturated end groups.