Modification of methylaluminoxane-activated ansa-zirconocene catalysts with triisobutylaluminum-transformations of reactive cations studied by NMR spectroscopy

Dmitrii E Babushkin; Hans H Brintzinger

doi:10.1002/chem.200601801

Modification of methylaluminoxane-activated ansa-zirconocene catalysts with triisobutylaluminum-transformations of reactive cations studied by NMR spectroscopy

Chemistry. 2007;13(18):5294-9. doi: 10.1002/chem.200601801.

Authors

Dmitrii E Babushkin¹, Hans H Brintzinger

Affiliation

¹ Boreskov Institute of Catalysis, Russian Academy of Science, Prospekt Akad.Lavrent'eva 5, 630090 Novosibirsk, Russia.

PMID: 17385201
DOI: 10.1002/chem.200601801

Abstract

When triisobutylaluminum (AliBu(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(mu-Me)(2)Me(4-x)iBu(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(mu-Me)(2)AlMe(2) (+)] to rac-[Me(2)Si(ind)(2)Zr(mu-Me)(2)AlMeiBu(+)] and rac-[Me(2)Si(ind)(2)Zr(mu-Me)(2)AliBu(2) (+)]. These species are unstable and release isobutene under formation of zirconocene hydrides.