Binuclear Heteroligated Titanium Catalyst Based on Phenoxyimine Ligands: Synthesis, Characterization, and Ethylene (Co)polymerization

A binuclear heteroligated titanium(IV) catalyst based on phenoxyimine ligands (FI 2 -Ti 2 ) with its crystal structure elucidated has been developed for the first time for olefin (co)polymerization. In ethylene polymerization, the activity of the binuclear catalyst FI 2 -Ti 2 can reach 3.0 × 106 g mol–1 h–1, and the polydispersity of the resulting polymers is narrow. In copolymerization of ethylene and other olefins, similar incorporation ratios for monoenes are obtained for FI 2 -Ti 2 and FI-Ti 1 . However, the incorporation ratio of 1,5-hexadiene increases from 3.2% using FI-Ti 1 to 8.8% with FI 2 -Ti 2 . In comparison, the binuclear monophenoxyimine catalyst, [FI 2 -Ti 2 (THF) 2 ], exhibits higher catalytic activity and incorporates more α-olefins than its mononuclear analogue [FI-Ti 1 (THF)] in the copolymerization. These results are interpreted as consequences of two effects. First, the cooperativity between the two metal centers facilitates the coordination of olefin. Second, the substitutions near the active sites exert a steric effect by blocking and suppressing the binding of comonomers.