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Modification of Methylaluminoxane‐Activated ansa ‐Zirconocene Catalysts with Triisobutylaluminum—Transformations of Reactive Cations Studied by NMR Spectroscopy
Author(s) -
Babushkin Dmitrii E.,
Brintzinger Hans H.
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601801
Subject(s) - methylaluminoxane , cationic polymerization , chemistry , adduct , catalysis , nuclear magnetic resonance spectroscopy , metallocene , polymer chemistry , organometallic chemistry , medicinal chemistry , nmr spectra database , crystallography , stereochemistry , polymerization , organic chemistry , spectral line , physics , astronomy , polymer
When triisobutylaluminum (Al i Bu 3 ) is added to solutions containing methylaluminoxane (MAO) and rac ‐[Me 2 Si(ind) 2 ZrCl 2 ] (ind: indenyl) in C 6 D 6 , NMR spectra show that methyl‐bridged mixed‐alkylaluminum dimers Al(μ‐Me) 2 Me 4− x i Bu x predominate. These dimers react with MAO under partial transfer of isobutyl groups and induce a conversion of the initially prevailing cationic trimethylaluminum adduct rac ‐[Me 2 Si(ind) 2 Zr(μ‐Me) 2 AlMe 2 + ] to rac ‐[Me 2 Si(ind) 2 Zr(μ‐Me) 2 AlMe i Bu + ] and rac ‐[Me 2 Si(ind) 2 Zr(μ‐Me) 2 Al i Bu 2 + ]. These species are unstable and release isobutene under formation of zirconocene hydrides.