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

[Image: see text] The dichloro titanium complexes (OSSO(tBu))TiCl(2) (1) and (OSSO(Cum))TiCl(2) (2) bearing o-phenylene-bridged OSSO-type ligands [OSSO(tBu)-H = 6,6′-((1,2-phenylenebis(sulfanediyl))bis(methylene))bis(2,4-di-tert-butyphenol) and OSSO(Cum)-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 1 revealed that Ti atom has an octahedral coordination geometry with an fac–fac wrapping of the [OSSO] ligand. In solution at 25 °C, 1 mainly retains the C(2) symmetric structure, whereas 2 shows an equilibrium between C(2)- and C(1)-symmetric stereoisomers. Activation of 2 with (Ph(3)C)[B(C(6)F(5))(4)] led to a highly active catalytic system with an activity of 238 kg(PE)·mol(cat)(–1)·bar(–1)·h(–1); linear polyethylene with a T(m) of 122 °C and M(w) of 107 kDa were obtained under these conditions. Catalyst 1 displayed the moderate activity of 59 kg(PE)·mol(cat)(–1)·bar(–1)·h(–1). 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 2 was also active in propylene polymerization producing atactic oligomers terminated with unsaturated end groups.