Synthesis of Tritertbutylphosphinimine Phenoxy Titanium Complexes and Their Catalytic Performance to Ethylene Polymerization

Tritertbutylphosphinimine phenoxy titanium complexes (f-Bu-3)PNTi(OAr)C1(2) [Ar=C6H5(4a), 2,6-Me2C6H3 (4b), 2,6-i-Pr2C6H3 (4c) and 2,6-t-Bu2C6H3 (4d)] were synthesized via the reaction of corresponding substituted phenol lithium salts with tritertbutylphosphinimine trichloride titanium (3). The compounds were characterized by means of H-1 NMR, C-13 NMR, P-31 NMR spectroscopic and elemental analyses, and the molecular structures of 3, 4b and 4d were further confirmed by single-crystal X-ray diffraction analysis. When activated with methylaluinoxanee (MAO), 4a similar to 4d displayed not only high catalytic activities, but also increasing performances on ethylene polymerization with increainmg the sterical hindrance of substituents. Furthermore, 4c depicted a good thermal stability, with which the polyethylene products of different molecular weights and molecular weight distributions can be obtained by tuning the polymrinzation conditions.