| Abstract: | The new dinuclear half‐sandwich CGC (constrained geometry catalyst) with methyl substitution in indenyl, [Ti(η5:η1‐2‐methylindenyl)SiMe2NCMe3]2 [(CH2)n] [n = 6 ( 10 ), n = 9 ( 11 ), n = 12 ( 12 )], have been synthesized, and structure of these complexes has been characterized by 1H and 13C NMR. The most important feature is that two protons of methylene directly bonded to the indenyl ring become inequivalent to be shown as two separated resonances at 2.9 and 3.0 ppm, probably due to the formation of planar chirality caused by a titanium complex formation. It has been found that the dinuclear CGCs with methyl substitution at an indenyl ring were very active catalysts for ethylene and styrene copolymerization. The activity increases in the order of 10 < 11 < 12 , which indicates that the presence of a longer bridge between two active sites contributes to facilitate the polymerization activity of the dinuclear CGC more effectively. This result might be understood by the implication that the steric factor rather than the electronic factor may play a major role to direct the polymerization behavior of the dinuclear CGC. It is found that the dinuclear catalysts are very efficient to incorporate styrene in the polyethylene backbone. The styrene contents in the formed copolymers ranged from 5 to 40% according to the polymerization conditions. One can observe strong signals at 29.7 ppm of the polyethylene sequences, and, in addition, peaks at 27.5, 36.9, and 46. 2ppm (Sβδ, Sαδ, and Tδδ, respectively) of sequences of EESEE. Weak peak at 25.3 ppm are attributed to Sββ, which represents SES sequence. The absence of a signal for Tββ at 41.3 ppm and for Sαα at 43.6 ppm shows there is no styrene–styrene sequences in copolymers. This result indicates that the dinuclear CGC are very effective to generate well‐distributed poly(ethylene‐co‐styrene)s. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1712–1723, 2004 |
