Bis(1,3-di-tert-butylimidazolin-2-iminato) titanium complexes as effective catalysts for the monodisperse polymerization of propylene

Manab Sharma, Haneen Simaan Yameen, Boris Tumanskii, Sabina Alexandra Filimon, Matthias Tamm*, Moris S. Eisen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

The use of bis(1,3-di-tert-butylimidazolin-2-iminato) titanium dichloride (1) and dimethyl (2) complexes in the polymerization of propylene is presented. The complexes were activated using different amounts of methylalumoxane (MAO), giving in each case a very active catalytic mixture and producing polymers with a narrow molecular weight distribution (polydispersity = 1.10). The use of the cocatalyst triphenylcarbenium (trityl) tetra(pentafluorophenyl)borate totally inhibits the reaction, producing the corresponding bis(1,3-di-tert- butylimidazolin-2-iminato) titanium(III) methyl complex, the trityl radical (CPh3), the anionic MeB(C6F5)4 -, B(C6F5)3, and the bis(1,3-di-tert-butylimidazolin-2-iminato) titanium(IV) dimethyl·B(C 6F5)3 complex. The use of a combination of physical methods such as NMR, ESR-C60, and MALDI-TOF analyses enabled us to propose a plausible mechanism for the polymerization of propylene, presenting that the polymerization is mainly carried out in a living fashion. In addition, we present a slow equilibrium toward a small amount of a dormant species responsible for 2,1-misinsertions and chain transfer processes.

Original languageEnglish
Pages (from-to)17234-17244
Number of pages11
JournalJournal of the American Chemical Society
Volume134
Issue number41
DOIs
StatePublished - 17 Oct 2012
Externally publishedYes

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