Stereoregular polymerization of α-olefins catalyzed by chiral group 4 benzamidinate complexes of C1 and C3 symmetry

Claudia Averbuj, Edith Tish, Moris S. Eisen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

153 Scopus citations

Abstract

The chiral lithium (-)-trimethylsilylmyrtanyl amide reacts with benzonitrile yielding the chiral benzamidinate lithium ligand ([N- trimethylsilyl][N'-myrtanyl]benzamidinate Li-TMEDA (TMEDA = tetramethylethylenediamine), [N(R*)-C-N]Li. An X-ray study shows that the ligand has a distorted tetrahedral environment in which the lithium atom is arranged symmetrically between the two benzamidinate and the two TMEDA nitrogen atoms. Equimolar addition of [N(R*)-C-N]Li to TiCl4 in THF yields [N(R*)-C-N]-TiCl3·THF (1). An X-ray study of 1 shows that it has an octahedral structure with the oxygen atom and one chlorine atom at the apical positions. [N(R*)-C-N]3ZrCl·toluene (2) can be prepared in a manner related to that employed to synthesize 1. An X-ray study of 2 shows that it has a capped octahedral geometry with the three trimethylsilyl groups in a cis position with respect to the chlorine atom and the other three myrtanyl groups arranged On the opposite side of the chlorine. Addition of MeLi·LiBr to complex 2 yields [N(R*)-C-N]3ZrMe (3) which is obtained as cocrystalline with complex 2. The X-ray structure of the cocrystalline mixture is similar to that of the chloride complex 2 exhibiting a Zr-Me distance of 2.469(10) Å. Complex 1 is an active catalyst, under pressure, for the polymerization of propylene producing elastomeric polypropylene and for the syndiotactic polymerization of styrene. Complex 2 was found to be active for the highly stereospecific polymerization of propylene.

Original languageEnglish
Pages (from-to)8640-8646
Number of pages7
JournalJournal of the American Chemical Society
Volume120
Issue number34
DOIs
StatePublished - 2 Sep 1998
Externally publishedYes

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