Ethylene Copolymerization with 1-Octene Using a 2-Methylbenz[e]indenyl-Based ansa-Monocyclopentadienylamido Complex and Methylaluminoxanes Catalyst

A new effective constrained geometry catalyst precursor for the ethylene/1-octene copolymerization, namely 2-methylbenz[e]indenylamido complex [eta5:eta1-(2-MeBenzInd)SiMe2NtBu]TiCl2 (4), was synthesized. Activated with methylaluminoxane (MAO), the complex 4 showed (a) an improved copolymerization activity and stability, (b) an enhanced comonomer incorporation in the copolymer, and (c) most importantly, an increased copolymer molecular weight, when compared with the previously employed catalysts. The polymerization conditions were found to have a significant effect on the catalyst activity, 1-octene incorporation, molecular weight, and even copolymer microstructure. For the copolymerization parameters, the values rE approximately 2.20 for ethylene and rO approximately 0.55 for 1-octene with rE.rO approximately 1.21 were obtained, reflecting a pronounced tendency for the random distribution of the comonomers in the copolymer chain. The 13C NMR analysis revealed that the E-O copolymer generated by the MAO-activated complex 4 has a regioirregular arrangement of the 1-octene repeat units as a result of some tail-to-tail incorporation of the 1-octene comonomer.