Abstract
A novel xanthene-bridged bissalicylaldiminato tridentate [ONS] ligand ligated binuclear titanium complex Ti2L bearing oxo-bridged macrocyclic structure were synthesized and characterized by 1H NMR, IR and elemental analysis. This binuclear complex Ti2L 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 × 106 g/molTi·h for ethylene polymerization upon activation with modified methylaluminoxane (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′, Ti2L 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.
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