Copolymerization of Ethylene with Isobutylene and Limonene Catalyzed by Titanium Complexes with Various ansa-(Fluorenyl)(alkylamido) Ligand

A series of titanium complexes bearing ansa-(fluorenyl)(amido) ligands with cyclohexylamido, isopropylamido, and isobutylamido groups were synthesized and their catalytic behaviors for the copolymerization of ethylene with isobutylene were compared with those with cyclododecylamido and tert-butylamido groups. The effects of cocatalyst on the ethylene-isobutylene copolymerization by a titanium complex having ansa-(fluorenyl)(cyclododecylamido) ligand were examined. The catalytic activity of the titanium complex for ethylene-limonene copolymerization was also further investigated

The Influence of t-Butyl and Cyclododecyl Substitution on Ethylene/1-Hexene Copolymerization Using Ansa-Fluorenylamidodimethyltitanium Derivatives

In the present study, copolymerization of ethylene and 1-hexene was conducted with a series of ansa-fluorenylamidodimethyltitanium complexes, including [t-BuNSiMe2Flu]TiMe2 (complex 1), [cyclododecylNSiMe2Flu]TiMe2 (complex 2) and [t-BuNSiMe2(2,7-t-Bu2Flu)]TiMe2 (complex 3), activated by MMAO. The effect of these catalysts on catalytic behavior, namely activity, molecular weight and monomer reactivity ratios, has been investigated. The results showed that all of them acted by a single site polymerization mechanism and the molecular weight distribution is independent of catalyst structure. Based on the study, it revealed that the introduction of a t-butyl at the 2,7 position on the fluorenyl ligand is able to enhance both catalytic activity and copolymer molecular weight more than introducing a cyclododecyl on the amine, which is probably associated with the electronic effect exerted by the t-butyl substituent. The comonomer incorporation content was controllable over a wide range by adjusting the comonomer feed ratio. Moreover, referring to monomer reactivity ratio exploration, it seems that the substitution on the ansa-fluorenylamidodimethyltitanium complex tends to hinder the insertion of 1-hexene into the polymer chain, leading to the highest 1-hexene content for traditional complex 1