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Isotactic 1-butene polymerization promoted by C2-symmetric metallocene catalysts

✍ Scribed by Anna Borriello; Vincenzo Busico; Roberta Cipullo; Ofelia Fusco; John C. Chadwick

Publisher
John Wiley and Sons
Year
1997
Tongue
English
Weight
631 KB
Volume
198
Category
Article
ISSN
1022-1352

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✦ Synopsis

Abstract

1‐Butene polyinsertion promoted by two typical C~2~‐symmetric zirconocene catalysts (i.e. rac‐ethylenebis(1‐indenyl)ZrCl~2~ (1) and rac‐dimethylsilylbis(1‐indenyl)ZrCl~2~) (2) was investigated under both hydrooligomerization and polymerization conditions and compared with that of propene. It was found that, in spite of a similar regiospecificity for the two monomers, the fraction of “dormant” sites is higher in 1‐butene polymerization, as a result of a (much) lower reactivity of a 2,1 last‐inserted unit. Accordingly, in the investigated cases, 2,1 units of 1‐butene were not incorporated in the growing chains but either isomerized to 4,1 units or remained at the chain end until they underwent chain transfer via β‐hydrogen elimination. Experimental evidence is also presented of an epimerization reaction of the growing poly(1‐butene) chain with a 1,2 last‐inserted unit, leading to a decrease of polymer stereoregularity with decreasing monomer concentration.

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