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Increase of catalyst activity by transfer of bulky alkyl groups from zirconocene complexes to methylalumoxane
Author(s) -
Denner Christine E.,
Alt Helmut G.
Publication year - 2003
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.12259
Subject(s) - alkyl , metallocene , polymer chemistry , chemistry , catalysis , monomer , ethylene , polymerization , post metallocene catalyst , metal , medicinal chemistry , organic chemistry , polymer
The activity of metallocene catalysts in ethylene polymerization can be increased by a factor of up to 3.5 when the corresponding metallocene catalyst precursors possess one or two bulky alkyl ligands such as benzyl groups instead of the conventional chloro ligands. We assume that in the activation process with methylalumoxane (MAO) these bulky alkyl groups are transferred from the metal to the MAO cocatalyst. The actual cocatalyst is supposed to be a cage with one or more monomeric AlMe 3 molecules inside. The bulky alkyl group is transferred to such an AlMe 3 unit and can act as a spacer separating the catalytically active metallocenium cation from the MAO anion. This effect is supposed to be responsible for the increase in activity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1336–1340, 2003