A novel tridentate [ONS] binuclear titanium complex bearing oxo-bridged macrocyclic structure for ethylene polymerization

A novel xanthene-bridged bissalicylaldiminato tridentate [ONS] ligand ligated binuclear titanium complex (TiL)-L-2 bearing oxo-bridged macrocyclic structure were synthesized and characterized by H-1 NMR, IR and elemental analysis. This binuclear complex (TiL)-L-2 was also investigated by single-crystal X-ray diffraction, which demonstrated C2 symmetric structure with each titanium coordinated with six atoms and formed a distorted octahedral configuration. The two titanium centers were also bridged by an oxygen atom to form a relatively stable macrocyclic structure. The binuclear complex exhibited excellent activity up to 1.99 x 10(6) g/molTi.h for ethylene polymerization upon activation with modified methyl-aluminoxane (MMAO), producing high molecular weight polyethylene with bimodal distribution. The reaction conditions, such as ethylene pressure, Al/Ti molar ratios and reaction temperatures, were found to have great influence on catalytic activity and polymer properties. Compared with the corresponding mononuclear analogue TiL', (TiL)-L-2 showed similar catalytic activity towards ethylene polymerization but produced polymer with lower molecular weight and much wider polydispersities (6.74-20.88), suggesting that two different active centers were present in this binuclear complex. (C) 2017 Elsevier B.V. All rights reserved.