108012-21-1Relevant articles and documents
Ethylene-bridged pseudo-Cs symmetric ansa-zirconocene complexes: Synthesis, structures and propylene polymerization behavior
Lee, Min Hyung,Park, Je-Woo,Hong, Chang Seop,Woo, Seong Ihl,Do, Youngkyu
, p. 37 - 47 (1998)
The ethylene-bridged pseudo-Cs symmetric ansa-zirconocene complexes, (1-fluorenyl-2-cyclopentadienylethane)zirconium dichloride (5a) and (1-fluorenyl-2-tetramethylcyclopentadienylethane)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.
Dialkoxy-substituted, C1-symmetric metallocenes: Synthesis and catalytic behavior in the propylene polymerization reaction
Schl?gl, Martin,Rieger, Bernhard
, p. 233 - 240 (2004)
The synthesis of a series of C1-symmetric metallocene complexes rac-[1-(5,6-dialkoxy-2-methyl-1-η5-indenyl)-2-(9-η 5-fluorenyl)ethane]zirconium dichlorides (alkyl: n-butyl, n-hexyl, n-octyl, n-decyl) is described. These co
Asymmetric ethylene-bridged metallocenes useful as catalysts in the polymerization of olefins and process for preparing said metallocenes
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, (2008/06/13)
Novel asymmetric ethylene-bridged metallocenes useful as catalysts in the polymerization of olefins and process for preparing said metallocenes. The novel metallocenes are represented by the general formula: wherein M represents a transition metal selected from titanium, zirconium and hafnium and X and X' represent a halogen atom. Preferably, the transition metal is Zr and the halogen atoms are both chlorine. Process for producing the novel metallocenes of general formula (I) comprising the steps of: a) reacting fluorenyllithium with 1,2-dibromoethane to produce 1-(9-fluorenyl)-2-bromoethane, b) reacting the said 1-(9-fluorenyl)-2-bromoethane with 2,4,7-trimethylindenyllithium to produce 1-(9-fluorenyl)-2-[1-(2,4,7-trimethyl)indenyl]ethane precursor, c) reacting the said 1-(9-fluorenyl)-2-[1-(2,4,7-trimethyl)indenyl]ethane precursor with butyllithium to produce its dilithium salt and d) reacting the said dilithium salt with a transition metal halide selected from halides of Ti, Zr and Hf to produce the metallocenes. The novel metallocenes are useful as catalysts for the polymerization of olefins such as ethylene and propylene and, in particular, for the production of higly isotactic polypropylene.
