Homo- and copolymerization of ethylene and α-olefins over 1- and 2-siloxy-substituted ethylenebis(indenyl)zirconium and ethylenebis(tetrahydroindenyl)zirconium dichlorides

A1 Journal article (refereed)

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Publication Details

List of Authors: Lehmus P, Kokko E, Harkki O, Leino R, Luttikhedde HJG, Nasman JH, Seppala JV
Publication year: 1999
Journal: Macromolecules
Journal acronym: MACROMOLECULES
Volume number: 32
Issue number: 11
Start page: 3547
End page: 3552
Number of pages: 6
ISSN: 0024-9297


The influence of siloxy substitution of ethylene-bridged bis(indenyl)- and bis(tetrahydro-indenyl)zirconium dichlorides on ethylene/alpha-olefin copolymerization and ethylene homopolymerization performance was investigated. Ethylene was copolymerized with 1-hexene and 1-hexadecene over rac-[ethylenebis(1-(tert-butyldimethylsiloxy)-3-indenyl)]zirconium dichloride (1), rac-[ethylenebis(1-(tert-butyldimethylsiloxy)-4,5,6,7-tetrahydro-3-indenyl)]zirconium dichloride (H1), rac-[ethylenebis(2-(tert-butyldimethylsiloxy)-1-indenyl)] zirconium dichloride (2), and rac-ethylenebis(1-indenyl)zirconium dichloride (EBI) using methylaluminoxane (MAO) as cocatalyst. 1-Siloxy substitution was found to remarkably improve the copolymerization ability and 2-siloxy substitution to enhance the polymerization activity of ethylenebis(indenyl)zirconium dichlorides. Optimum homo- and copolymerization performance was observed at a very low Al(MAO) concentration, which for 2 could be reduced to a level of 0.2 mmol/dm(3) by using a small amount of triisobutylaluminum. The 1-siloxy-substituted metallocene catalysts 1 and H1 (hydrogenated 1) revealed decreasing comonomer incorporation and increasing induction times with increasing Al(MAO) concentration, which indicates the presence of unfavorable interactions between these metallocenes and MAO. Chain termination occurred mainly by chain transfer to the monomer and beta-hydrogen transfer to the metal for catalysts with indenyl and tetrahydroindenyl ligands, respectively.

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