("Ferrocene-salaldiminato") Zirconium complexes for ethylene polymerization catalysis: The role of the bulky substituents

Xiaowu Wang, Roland Fröhlich, Constantin G. Daniliuc, Bernhard Rieger, Aleksandra Jonovic, Gerald Kehr, Gerhard Erker

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

We prepared the 2-hydroxy-5-trimethylsilylferrocenecarbaldimine systems 13 enantioselectively by a short synthetic route starting from the chiral ferrocene carbaldehyde acetal 5. The imines 13a-c were used to synthesize the zwitterionic ("ferrocene-salaldiminato") 2ZrCl 4 complexes 14a-c. Activation with MAO gave homogeneous Ziegler-Natta catalysts, which showed only a moderate ethylene polymerization activity, similar to the unsubstituted parent "ferrocene-salaldiminato" zirconium systems. Consequently, a synthetic route was devised and carried out to make the corresponding 2-hydroxy-3,5-bis(trimethylsilyl)ferrocenecarbaldimines (21) available. The enantiomerically highly enriched ligands (pS)-21a and -d derived from the aldehyde and aniline or cyclohexylamine, respectively, were used to synthesize the corresponding ("ferrocene-salaldiminato") 2ZrCl 4 complexes 22a,d. Both gave highly active homogeneous Ziegler-Natta catalysts upon activation with MAO for the formation of linear low molecular weight polyethylene. Complex 22d and many ligand precusors from both sequences were characterized by X-ray diffraction.

Original languageEnglish
Pages (from-to)6741-6752
Number of pages12
JournalOrganometallics
Volume31
Issue number19
DOIs
StatePublished - 8 Oct 2012

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