Syndiospecific living catalysts for propylene polymerization: Effect of fluorination on activity, stereoselectivity, and termination

The polymerization of propylene using a variety of fluorinated bis(phenoxyimine)titanium complexes is reported. The synthesis of ten complexes containing varying fluorinated N-aryl substituents is described. X-ray structural and solution NMR data indicate that these complexes are C-2-symmetric in the solid state, although in some cases C-1-symmetric isomers are observed in solution. When activated with methylalumoxane, all complexes formed syndiotactic polypropylene. Catalysts with ortho-fluorine substituents formed polymers with very narrow molecular weight distributions, indicative of a living polymerization. Catalysts with fluorine in at least the ortho and para positions exhibited the highest syndio-specificities. Catalysts with meta- or para-fluorine-containing substituents were more active for propylene polymerization than the corresponding non-fluorinated catalyst.