Titanium complexes bearing aromatic-substituted β-enaminoketonato ligands: Syntheses, structure and olefin polymerization behavior

A series of titanium complexes [(Ar)NC(CF3)CHC(R)O]2TiCl2 (4b: Ar = –C6H4OMe(p), R = Ph; 4c: Ar = –C6H4Me(p), R = Ph; 4d: Ar = –C6H4Me(o), R = Ph; 4e: Ar = α-Naphthyl, R = Ph; 4f: Ar = –C6H5, R = t-Bu; 4g: Ar = –C6H4OMe(p); R = t-Bu; 4h: Ar = –C6H4Me(p); R = t-Bu; 4i: Ar = –C6H4Me(o); R = t-Bu) has been synthesized and characterized. X-ray crystal structures reveal that complexes 4b, 4c and 4h adopt distorted octahedral geometry around the titanium center. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 4b–c and 4f–i are active catalysts for ethylene polymerization and ethylene/norbornene copolymerization, and produce high molecular weight polyethylenes and ethylene/norbornene alternating copolymers. In addition, the complex 4c/MMAO catalyst system exhibits the characteristics of a quasi-living copolymerization of ethylene and norbornene with narrow molecular weight distribution.