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C1-Symmetric Heterocyclic Zirconocenes as Catalysts for Propylene Polymerization, 1

✍ Scribed by Ilya E. Nifant'ev; Ilya Laishevtsev; Pavel V. Ivchenko; Igor A. Kashulin; Simona Guidotti; Fabrizio Piemontesi; Isabella Camurati; Luigi Resconi; Peter A. A. Klusener; Jos J. H. Rijsemus; Kees P. de Kloe; Frans M. Korndorffer

Publisher
John Wiley and Sons
Year
2004
Tongue
English
Weight
324 KB
Volume
205
Category
Article
ISSN
1022-1352

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✦ Synopsis

Abstract

Summary: The synthesis of C~1~‐symmetric zirconocene complexes bearing the 2,5‐dimethyl‐7__H__‐cyclopenta[1,2‐b:4,3‐b′]dithiophene ligand (S~2~‐3) linked to substituted cyclopentadienes is described. Different syntheses of S~2~‐3, the common intermediate for the preparation of these complexes, are discussed. Many of these complexes have been found to be highly active in propylene polymerization, to require very low amounts of methylalumoxane to be activated, and to produce poly(propylene)s of low isotacticity and melting points. ^13^C NMR analysis shows that the poly(propylene)s are fully regioregular and that the stereoerrors are randomly distributed, as shown by the enantiomorphic‐site triad test E ≈ 1. The experimental pentad distribution was fitted using a two‐site model with different probability parameters for each site. The probability of chain back‐skip was also taken into account. The molecular weight and crystallinity of the poly(propylene)s are dependent upon the type of substituents on the cyclopentadienyl ring, and the correlation between mmmm content and melting point of the PP confirms the random distribution of stereoerrors.

Correlation between % mmmm pentad and melting point.

magnified imageCorrelation between % mmmm pentad and melting point.

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