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Silica-supported metallocenes: stereochemical comparison between homogeneous and heterogeneous catalysis

✍ Scribed by Maria Carmela Sacchi; Debora Zucchi; Incoronata Tritto; Paolo Locatelli; Tiziano Dall'Occo

Publisher: John Wiley and Sons
Year: 1995
Tongue: English
Weight: 442 KB
Volume: 16
Category: Article
ISSN: 1022-1336
DOI: 10.1002/marc.1995.030160807

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✦ Synopsis

Abstract

Propylene was polymerized in the presence of the isospecific Et(Ind)~2~ZrCl~2~ (Et: ethylene, Ind: indenyl) and the aspecific (Ind)~2~ZrCl~2~ complexes in solution and anchored to SiO~2~ and SiO~2~/MAO (MAO: methylaluminoxane) supports. From the stereochemical analysis of the polypropene samples obtained it can be deduced that (i) the same active species is formed when a metallocene is in solution and when it is anchored to the SiO~2~/MAO support and (ii) a completely different active species is formed when the metallocene is anchored to the silica. The fact that both systems Et(Ind)~2~ZrCl~2~SiO~2~ and (Ind)~2~ZrCl~2~SiO~2~ produce the same prevailingly isospecific polymer suggests that only isospecific centers are formed in this case, independently of the metallocene stereochemical structure.

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