Tailored Ru‐NHC Heterogeneous Catalysts for Alkene Metathesis

Karamé, Iyad; Boualleg, Malika; Camus, Jean‐Michel; Maishal, Tarun K.; Alauzun, Johan G.; Basset, Jean‐Marie; Copéret, Christophe; Corriu, Robert J. P.; Jeanneau, Erwan; Mehdi, Ahmad; Reyé, Catherine; Veyre, Laurent; Thieuleux, Chloé

doi:10.1002/chem.200901752

Cited by 72 publications

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“…Additionally, a very weak broad signal at d = 48 ppm could also be observed and was attributed to pentavalent phosphorus, which probably resulted from side reaction with the surface leading to a phosphonium or phosphine oxide species. [17] Moreover, the 13 C-labelled sample, MÀRuP*, displayed a signal at d = 172 ppm in the CPMAS 13 C NMR spectrum, which was in agreement with NHC bonded to Ru (see Figure S7 in the Supporting Information). Although it is not possible to give an exact structure for the surface complex(es), it is clear that it corresponds to ruthenium complex(es) bound to one NHC and inequivalent PMe 3 ligands.…”

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confidence: 57%

“…Based on the direct synthesis of hybrid materials synthesis, we recently developed imidazolium-functionalised materials and the corresponding iridium [14] and ruthenium [13,14] NHC catalytic materials for H/D exchange and alkene metathesis reactions. Their very high catalytic performances, typically equalling or exceeding those of their homogeneous counterparts, are owed to the control of the synthesis of the catalytic material at the molecular level.…”

Section: Dedicated To Christian Bruneau On the Occasion Of His 60th Bmentioning

confidence: 99%

“…The optimal experimental conditions were the deprotonation of 1-mesityl-3-[3-(triisopropoxysilyl)propyl]imidazolium iodide with KHDMS in THF followed by subsequent treatment with [{RuCl 2 (p-cymene)} 2 ]. The expected Ru Cym complex (see Scheme 1 and Figure S1 in the Supporting Information) was isolated in 59 % yield and fully characterised by using elemental analysis and solution-state NMR spectroscopy ( 1 H, 13 C, COSY, 13 C-1 H HSQC). Using these optimised conditions, we studied the formation of heterogeneous homologue systems MÀRu Cym based on the use of imidazolium-functionalised mesostructured silica prepared by using a direct synthesis pathway using a templating route.…”

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confidence: 99%

“…This solid was obtained in a controlled manner by use of hybrid organic-inorganic mesostructured silica materials, designed by using a sol-gel process through a templating route, and in situ transformations of the pendant organic functionalities into RuÀNHC moieties. These materials were fully characterised by using several techniques, in particular, solid-state NMR spectroscopy on 13 C labelled materials (in the carbenic carbon atom), thus enabling the observation of unique RuÀNHC units within the materials. These systems displayed very promising activities in the hydrogenation of CO 2 , but suffered from metal leaching, which evidenced the weakness of the NHCÀRu linkage under these reaction conditions.…”

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confidence: 99%

“…Further analysis of the solvent residue of grafting by GC and GC-MS showed the presence of para-cymene (0.25 equiv per Ru), thus implying its replacement by THF (25 % after 3 h of grafting). If MÀRu Cym was in contact with pure THF for 4 h at 40 8C, the 13 Note that the two signals at d = 26 and 68 ppm associated with protonated THF disappeared upon exposing the material to [D 8 ]THF for 1 h, as expected upon the exchange of protonated to deuterated THF, for which no signal enhancement was expected for 13 C with CPMAS NMR spectroscopy, hence the disappearance of those signals (see Figure S9 in the Supporting Information). Finally, to confirm that ruthenium was coordinated to the NHC systems, we used a 13 C-enriched imidazolium material for grafting (30 % in position 2, natural abundance elsewhere).…”

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confidence: 99%

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Tailored Ruthenium–N‐Heterocyclic Carbene Hybrid Catalytic Materials for the Hydrogenation of Carbon Dioxide in the Presence of Amine

et al. 2011

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Dedicated to Christian Bruneau on the occasion of his 60th birthdayThe use of CO 2 as a C 1 building block is one possible solution for CO 2 remediation; a point of particular interest considering that the atmospheric concentration of CO 2 is reaching critical values.[1] For instance, the hydrogenation of CO 2 back into chemicals and fuels [2] can be a potential approach. For this particular chemical process, homogeneous catalysts based on noble metals were first discovered in the 1970s, [3,4] but one critical advance was the use of ruthenium trimethylphosphine complexes and supercritical CO 2 as a "solvent". Depending on the additives present during the reaction, formic acid, [5] formamides, [6] or formate esters [7] are produced. The introduction of bidentate chelating ligands led to further improvements for the hydrogenation of CO 2 to formamides.[8] Ruthenium and iridium complexes with phosphorus-nitrogen-phosphorus pincer (PNP) [9] or bis-N-heterocyclic carbene (NHC) ligands [10] were also very effective for the hydrogenation of CO 2 to formic acid. Although homogeneous catalytic systems of this type are numerous, there are only a few examples of heterogeneous catalysts. Two main strategies have been developed to date: the coordination of different metal precursors to aminopropylfunctionalised materials [10] and the incorporation of trialkoxysilane-containing ruthenium phosphine complexes during a sol-gel process.[11] Whereas the former approach leads to significant metal leaching, the latter suffers from lower catalytic performances than their homogeneous analogues, owing possibly to reactant diffusion difficulties.[12] Considering the advantages of heterogeneous catalysts, there is still the need to develop supported catalysts by using a much more controlled approach, allowing the control of the distribution of active sites, and avoiding any problem of accessibility of the reactants to these sites. Based on the direct synthesis of hybrid materials synthesis, we recently developed imidazolium-functionalised materials and the corresponding iridium [14] and ruthenium [13,14] NHC catalytic materials for H/D exchange and alkene metathesis reactions. Their very high catalytic performances, typically equalling or exceeding those of their homogeneous counterparts, are owed to the control of the synthesis of the catalytic material at the molecular level. We therefore developed catalytic materials based on RuÀNHC species, which display promising catalytic performances, for the hydrogenation of CO 2 to amides.Firstly, the synthesis of the molecular complex [RuCl 2 (pcymene)(1-mesityl-3-{(3-triisopropoxysilyl)propyl}imidazol-2-ylidene)], Ru Cym , was performed (Scheme 1). It involved the formation of a free NHC (step 1) and the subsequent coordination of [{RuCl 2 (p-cymene)} 2 ] (step 2). The optimal experimental conditions were the deprotonation of 1-mesityl-3-[3-(triisopropoxysilyl)propyl]imidazolium iodide with KHDMS in THF followed by subsequent treatment with [{RuCl 2 (p-cymene)} 2 ]. The expected Ru Cym complex ...

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confidence: 57%