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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1. Synthesis of New heterogeneous catalysts through the controlled growth of inorganic nanostructures around monodispersed metal nanoparticles.
2. Well-Defined Single-Site Heterogeneous Ir-NHC Catalysts for H/D Exchange Reaction via Surface OrganoMetallic Chemistry on Hybrid Organic-Inorganic Materials