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Well-Defined Single-Site Heterogeneous Ru-NHC Catalysts for the metathesis of functionalized olefin Reaction via Surface OrganoMetallic Chemistry on Hybrid Organic-Inorganic Materials

Johan Alauzun 2Jean-Marie Basset 1Jean-Michel Camus 1Christophe Coperet 1Robert J. Corriu 2Iyad E. Karame 1Tarun Maishal 1Ahmad Mehdi 2Catherine Reyé 2Laurent Veyre 1Chloe M. Thieuleux 1

1. Chimie, Catalyse, Polymère, Procédé, UMR CNRS CPE UCBL (CCPP), 43 bd du 11 Nov. 1918, Villeurbanne 69616, France
2. Institut Charles Gerhardt, CC15, Place eugène Bataillon, Montpellier 34095, France

Abstract

In the past ten years, olefin metathesis has become a key reaction in organic synthesis and material science because of the emergence of highly active and selective homogeneous ruthenium catalysts1 tolerant to a large scope of functionalities. The best systems are currently based on Ru-complex having N-Heterocyclic Carbene (NHC) ligands. While several highly efficient homogeneous catalysts were developed, the corresponding heterogeneous catalysts have displayed poor efficiencies, despite numerous attempts.2 The best Ru-based heterogeneous catalysts can only transform about 5000 equivalents of diallylmalonate through RCM, and this is probably due to the difficulty to generate well-defined systems.

In contrast to classical grafting methods on oxides or polymer supported systems, we have synthesized organic-inorganic hybrid nanostructured materials as supports for Ru-NHC-complexes in order to obtain catalysts having regularly distributed active sites throughout the oxide matrix. The imidazolium-containing nanostructured materials were prepared by a Sol-Gel process usingtemplating routes, and the thus-obtained materials contain regularly distributed imidazolium moieties, covalently bonded to the pores channels of the nanostructured silica framework, as evidenced by several characterization techniques (TEM, X-Ray, solid state NMR spectroscopy…).

Then, Ru-complexes were selectively coordinated on the imidazolium moieties of the materials to generate Ru-NHC alkylidene surface species. These new catalytic systems were fully characterized and displayed very good performances in the metathesis of ethyl-oleate compared to other reported Ru-based heterogeneous systems.

A deep understanding of the nature of the active site was obtained using the stereochemistry of ethyl-oleate self-metathesis reaction at very low conversion and it was further corroborated by spectroscopic datas (13C Solid state NMR) performed on very similar material containing Ir-NHC 13C labelled complexes.

 

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Related papers

Presentation: Poster at E-MRS Fall Meeting 2008, Symposium D, by Chloe M. Thieuleux
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-27 11:26
Revised:   2009-06-07 00:44