Copolymerization of propene and nonconjugated diene involving intramolecular cyclization with metallocene/methylaluminoxane

Copolymerizations of propene with 1,5-hexadiene and 1,7-octadiene were carr ied out with isospecific rac-dimethylsilylenebis(indenyl)zirconium dichlori de (1) and syndiospecific diphenylmethylene(cyclopentadienyl) (9-fluorenyl) zirconium dichloride (2), combined with methylaluminoxane. Microstructures of the copolymers were determined by H-1 NMR, C-13 NMR, and DEFT (distortio nless enhancement of polarization transfer) spectroscopies. Incorporation o f nonconjugated dienes in the copolymer was higher with 2 than with I. Intr amolecular cycloaddition of the nonconjugated dienes proceeded regardless o f the catalysts. Stereoselectivity in cycloaddition of 1,5-hexadiene was in vestigated based on the structures of isolated methylene-1,3-cyclopentane u nits. It was found that 1,5-hexadiene was inserted stereospecifically by en antiomorphic site control with both catalysts. The diastereoselectivity of the cyclization step of 1,2-inserted 1,5-hexadiene was, however, found to b e independent of stereospecificity of the catalyst. The cyclization selecti vity of 1,5-hexadiene copolymerization was higher than that of 1,7-octadien e copolymerization. 1 gave the copolymers with higher selective in cyclizat ion than 2 in the propene/1,5-hexadiene copolymerization, while the opposit e tendency was observed in the propene/1,7-octadiene copolymerization. Decr ease of cyclization selectivity was observed with the increases of 1,1,5-he xadiene and 1,7-octadiene concentration in both copolymerizations. Propene insertion could disturb the cyclization of 1,2-inserted dienes, which decli ned the cyclization selectivity of the copolymers, except propene/1,5-hexad iene copolymerization with 2.