Substituent Effects on the Stereospecificity of Propylene Polymerization by Novel Asymmetric Bridged Zirconocenes. A Mechanistic Discussion

The synthesis and polymerization behavior of a new C 1-symmetric bridged indenyl−fluorenyl zirconocene dimethylsilylene [9-fluorenyl][(2,4,7-trimethyl)indenyl]zirconium dichloride (5) is reported. The complex when activated by MAO was found to polymerize ethylene and propylene, although the activity...

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Bibliographic Details
Published in:Macromolecules 2000-03, Vol.33 (5), p.1546-1552
Main Authors: Thomas, Emma J, Chien, James C. W, Rausch, Marvin D
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Organic polymers
Physicochemistry of polymers
Polymerization
Preparation, kinetics, thermodynamics, mechanism and catalysts
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Summary:The synthesis and polymerization behavior of a new C 1-symmetric bridged indenyl−fluorenyl zirconocene dimethylsilylene [9-fluorenyl][(2,4,7-trimethyl)indenyl]zirconium dichloride (5) is reported. The complex when activated by MAO was found to polymerize ethylene and propylene, although the activity and stereoselectivity of 5 for propylene were found to be lower than for the previously prepared ethylene-bridged analogue 4 and several other ethylene-bridged precursors. It has been found that, depending on both the substitution patterns on the indenyl ligand and the nature of the bridge in this series of asymmetric zirconocenes, polypropylenes with varying microstructures from aspecific to highly isospecific are obtained. The propylene polymerization behavior of the new complexes has been studied in detail, and the mechanistic aspects of polymerization are discussed.
ISSN:0024-9297
1520-5835
DOI:10.1021/ma991463w