Homo- and Heteroligated Salicylaldiminato Titanium Complexes with Different Substituents <i>Ortho</i> to the Phenoxy Oxygens for Ethylene and Ethylene/1-Hexene (Co)polymerization

Abstract

A series of homoligated ( 1c – 1e ) and heteroligated ( 2a – 2e ) salicylaldiminato titanium dichloride complexes with different substituents ortho to the phenoxy oxygens were efficiently prepared. X-ray diffraction studies on these new dichloride complexes 2b, 2d, and 2e reveal a distorted octahedral coordination of the central metal. In the presence of dried methylaluminoxane, all the complexes exhibit high ethylene polymerization productivities. Surprisingly, complex 1d incorporating an o -(trimethylsilyl)ethynyl group displays the highest activity [5.26 × 10 3 kg of polyethylenes (mol Ti) −1 h –1 ]. In ethylene/1-hexene copolymerization, the heteroligated complexes 2a – 2e display improved activities and intermediate incorporation ability compared with their homoligated counterparts 1a – 1f . The activity and incorporation ability for 1-hexene are highly dependent on the nature of the ortho -substituents. Among them, (trimethylsilyl)ethynyl-substituted precatalyst ( 1d ) achieves the highest incorporation ratio (27.3 mol %), while ethynyl-substituted precatalyst ( 2c ) achieves the highest copolymerization activity [2.89 × 10 3 kg of copolymers (mol Ti) −1 h –1 ].