Ethylene-bridged pseudo-C-s symmetric ansa-zirconocene complexes: synthesis, structures and propylene polymerization behavior

The ethylene-bridged pseudo-C-s symmetric ansa-zirconocene complexes, (1-fluorenyl-2-cyclopentadienylethane)zirconium dichloride (5b), were synthesized and their molecular structures have been determined by single crystal X-ray diffraction studies. The complex 5a is very active toward propylene polymerization in the presence of methylaluminoxane (MAO), affording polypropylene with good syndiotacticity. In comparison with the known syndiotactic polypropylene catalytic system iPr(fluorenyl)(cyclopentadienyl)ZrCl2/MAO 5a/MAO system is better in thermal stability, higher in activity and lower in syndiotacticity under the identical polymerization conditions. On the other hand, 5b/MAO system shows low activity and produces nearly atactic polypropylene with low molecular weight, which could be attributed to the increased electron density and steric bulkiness around the metal center. (C) 1998 Elsevier Science S.A. All rights reserved.
Publisher
ELSEVIER SCIENCE SA
Issue Date
1998-06
Language
ENG
Keywords

ZIEGLER-NATTA CATALYSIS; M = ZR; METALLOCENE METHYLALUMINOXANE CATALYSTS; HOMOGENEOUS OLEFIN POLYMERIZATION; CONSTRAINED GEOMETRY CATALYSTS; PROPENE POLYMERIZATION; STEREOCHEMICAL CONTROL; CRYSTAL-STRUCTURES; SYNDIOTACTIC POLYPROPYLENE; METHYLALUMOXANE CATALYSTS

Citation

JOURNAL OF ORGANOMETALLIC CHEMISTRY, v.561, no.1-2, pp.37 - 47

ISSN
0022-328X
URI
http://hdl.handle.net/10203/2103
Appears in Collection
CH-Journal Papers(저널논문)
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