Ethylene homopolymerization and copolymerization with α-olefins catalyzed by titanium complexes bearing [O−NSR] tridentate ligands

A series of titanium complexes of the general formula [N-(3,5-di-tert-butylsalicylidene)-2-alkyl-sulfanylanilinato]Ti(IV)Cl3 (5a, b, e and f) exhibited very high catalytic activities in ethylene homo- and copolymerization with various α-olefins in the presence of modified methylaluminoxane (MMAO). The results showed that steric hindrance of the alkylthio groups in 5a–f strongly influenced the polymerization behavior. An increase in the steric hindrance of these alkyl units led to the decrease in both catalytic activity and comonomer incorporation ratio. On the other hand, the amount of α-olefin incorporated into the copolymer chain depended on the molar ratio of the monomers in the polymerization reaction and was slightly influenced by the chain length of α-olefin. Comparisons between alkylthio and arylthio substituents on catalyst performance were also discussed in this article.