Copolymerization behavior of titanium imidazolin-2-iminato complexes

Abstract

Monocyclopentadienyl titanium imidazolin-2-iminato complexes [Cp′Ti(L)X2] 1a (Cp′ = cyclopentadienyl, L = 1,3-di-tert-butylimidazolin-2-imide, X = Cl), 1b (X = CH3); 2 (Cp′ = cyclopentadienyl, L = 1,3-diisopropylimidazolin-2-imide, X = Cl); 3 (Cp′ = tert-butylcyclopentadienyl, L = 1,3-di-tert-butylimidazolin-2- imide, X = Cl), upon activation with methylaluminoxane (MAO) were active for the polymerization of ethylene and propylene and the copolymerization of ethylene and 1-hexene. Catalysts derived from imidazolin-2-iminato tropidinyl titanium complex 4 = [(Trop)Ti(L)Cl2] (Trop = tropidinyl, L = 1,3-di-tert-butylimidazolin-2-imide) were much less active. Narrow polydispersities were observed for ethylene and propylene polymerization, but the copolymerization of ethylene/hexene led to bimodal molecular weight distributions. The productivity of catalysts derived from the dialkyl complex 1b activated with [Ph3C][B(C6F5)4] or B(C6F5)3 were less active for ethylene/hexene copolymerization but yielded ethylene/hexene copolymers of narrower molecular weight distributions than those derived from 1a/MAO. © 2008 Wiley Periodicals, Inc.