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See detailSynthesis and Catalytic Evaluation in Olefin Metathesis of a Second-Generation Homobimetallic Ruthenium-Arene Complex Bearing a Vinylidene Ligand
Borguet, Yannick ULg; Sauvage, Xavier ULg; Zaragoza, Guillermo et al

in Organometallics (2011), 30(10), 2730-2738

The new homobimetallic ruthenium–vinylidene complex [(p-cymene)Ru(μ-Cl)3RuCl(═C═CHPh)(IMes)] (6) was isolated in high yield upon treatment of [(p-cymene)Ru(μ-Cl)3RuCl(η2-C2H4)(IMes)] (5) with a slight ... [more ▼]

The new homobimetallic ruthenium–vinylidene complex [(p-cymene)Ru(μ-Cl)3RuCl(═C═CHPh)(IMes)] (6) was isolated in high yield upon treatment of [(p-cymene)Ru(μ-Cl)3RuCl(η2-C2H4)(IMes)] (5) with a slight excess of phenylacetylene at −50 °C. Although it was very stable under normal atmosphere in the solid state, this product underwent an oxidative cleavage into the corresponding carbonyl compound [(p-cymene)Ru(μ-Cl)3RuCl(CO)(IMes)] (7) when dissolved in oxygen-containing solvents. Second-generation complexes 6 and 7 were characterized by IR and NMR spectroscopies, and their molecular structures were determined by X-ray diffraction analysis. The catalytic activity of complex 6 was probed in various types of olefin metathesis reactions. Compared to its first-generation analogue [(p-cymene)Ru(μ-Cl)3RuCl(═C═CHPh)(PCy3)], the new ruthenium initiator displayed an enhanced activity. It was also much more selective than ruthenium–ethylene complex 5. Aluminum chloride was a valuable cocatalyst for the ROMP of cyclooctene, whereas phenylacetylene was better suited to achieve the fast and quantitative RCM of α,ω-dienes into the corresponding di- or trisubstituted cycloolefins. The role of the terminal alkyne was rationalized by assuming that it would allow an enyne metathesis to take place, thereby transforming saturated vinylidene precursor 6 into a highly active mono- or bimetallic ruthenium–alkylidene species. [less ▲]

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See detailMixed Isobutylphobane/N-Heterocyclic Carbene Ruthenium-Indenylidene Complexes: Synthesis and Catalytic Evaluation in Olefin Metathesis Reactions
Sauvage, Xavier ULg; Zaragoza, Guillermo; Demonceau, Albert ULg et al

in Advanced synthesis & catalysis (2010), 352(11-12), 1934-1948

Two new second generation ruthenium(11) dichloride-indenylidene complexes [RuCl2(9-isobutylphosphabicyclo[3.3.1]nonane)(NHC)(3-phenyl-1-indenylide ne)1, where NHC,3-bis(2,4,6-tri-methylphenyl)imidazolin-2 ... [more ▼]

Two new second generation ruthenium(11) dichloride-indenylidene complexes [RuCl2(9-isobutylphosphabicyclo[3.3.1]nonane)(NHC)(3-phenyl-1-indenylide ne)1, where NHC,3-bis(2,4,6-tri-methylphenyl)imidazolin-2-ylidene (SIMes) or its unsaturated imidazol-2-ylidene analogue (1Mes). were isolated in high yields upon heating a tetrahydrofuran (THF) solution of the diphosphane complex [RuCl2(isobutylphobane)2(3-phenyl-1-indenylidene)] with a two-fold excess of the corresponding imidazol(in)ium-2-carboxylate zwitterions. Both products were characterized by H-1, C-13, and P-33 NMR spectroscopy, and the molecular structure of [RuCl2(isobutylphobane)(SIMes)(3-phenyl-1-indenylidene)] was determined by X-ray diffraction analysis. A close inspection of the packing structure revealed the presence of different types of intra- and intermolecular interactions that enhanced the global stability of the crystals, while low temperature NMR experiments showed the existence of two distinct rotational isomers due to the unsymmetrical nature of the phobane ligand The catalytic activity of both compounds was assessed in olefin metathesis using [less ▲]

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See detailHomobimetallic Ruthenium-Arene Complexes Bearing Vinylidene Ligands Synthesis, Characterization, and Catalytic Application in Olefin Metathesis
Borguet, Yannick ULg; Sauvage, Xavier ULg; Zaragoza, Guillermo et al

in Organometallics (2010), 29(24), 6675-6686

Five new arylvinylidene complexes with substituents ranging from electron donating to strongly withdrawing (p OMe p Me p Cl p CF3 and m (CF3)(2)) were isolated in high yields by reacting [(p cymene)Ru(mu ... [more ▼]

Five new arylvinylidene complexes with substituents ranging from electron donating to strongly withdrawing (p OMe p Me p Cl p CF3 and m (CF3)(2)) were isolated in high yields by reacting [(p cymene)Ru(mu Cl)(3)RuCl(eta(2) C2H4)(PCy3)] (3) with the corresponding phenylacetylene derivatives The known phenylvinylidene complex [(p cymene)Ru(mu Cl)(3)RuCl(=C=CHPh)(PCy3)] (5) was also obtained from [RuCl2(p cymene)](2) tricyclohexylphosphine and phenylacetylene under microwave irradiation The influence of the remote aryl substituents on structural features was investigated by IR NMR and XRD spectroscopes A very good linear relationship was observed between the chemical shift of the vinylidene alpha carbon atom and the Hammett sigma constants of the aryl group substituents The catalytic activity of the six homobimetallic complexes was probed in various types of olefin metathesis reactions Unsubstituted phenylvinylidene compound 5 served as a lead structure for these experiments Its reaction with norbornene afforded high molecular weight polymers with a broad polydispersity index and mostly trans double bonds Aluminum chloride was a suitable cocatalyst for the ring opening metathesis polymerization of cyclooctene and led to the formation of high molecular weight polyoctenamer with a rather narrow polydispersity index (M-w/M-n = 1 25) and an almost equimolar proportion of cis and trans double bonds No major changes were observed in the polymer yields and microstructures when complexes bearing donor groups on their aryl rings were employed as catalyst precursors On the other hand compounds bearing strongly electron withdrawing substituents were significantly less active Model vinylidene compound 5 and its ruthenium-ethylene parent (3) both required the addition of phenylacetylene to achieve the ring closing metathesis of diethyl 2 2 diallylmalonate Thus the role of this terminal alkyne cocatalyst goes beyond the facile replacement of the eta(2) alkene ligand with a vinylidene fragment [less ▲]

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See detailTandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium-arene complexes
Borguet, Yannick ULg; Sauvage, Xavier ULg; Zaragoza, Guillermo et al

in Beilstein Journal of Organic Chemistry (2010), 6

The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium-indenylidene complex [(p-cymene)Ru(mu-Cl)(3)RuCl(3-phenyl-1-indenylidene ... [more ▼]

The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium-indenylidene complex [(p-cymene)Ru(mu-Cl)(3)RuCl(3-phenyl-1-indenylidene)(PCy3)] (1) to generate active species in situ. The two catalytic processes were first carried out independently in a case study before the whole sequence was optimized and applied to the synthesis of several polyhalogenated bicyclic gamma-lactams and lactones from alpha,omega-diene substrates bearing trihaloacetamide or trichloroacetate functionalities. The individual steps were carefully monitored by H-1 and P-31 NMR spectroscopies in order to understand the intimate details of the catalytic cycles. Polyhalogenated substrates and the ethylene released upon metathesis induced the clean transformation of catalyst precursor 1 into the Ru(II)-Ru(III) mixed-valence compound [(p-cymene) Ru(mu-Cl)(3)RuCl2(PCy3)], which was found to be an efficient promoter for atom transfer radical reactions under the adopted experimental conditions. [less ▲]

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See detailMicrowave-Assisted Ruthenium-Catalyzed Reactions
Nicks, Francois ULg; Borguet, Yannick ULg; Delfosse, Sebastien et al

in Australian Journal of Chemistry (2009), 62(3), 184-207

Since the first reports on the use of microwave irradiation to accelerate organic chemical transformations, a plethora of papers has been published in this field. In most examples, microwave heating has ... [more ▼]

Since the first reports on the use of microwave irradiation to accelerate organic chemical transformations, a plethora of papers has been published in this field. In most examples, microwave heating has been shown to dramatically reduce reaction times, increase product yields, and enhance product purity by reducing unwanted side reactions compared with conventional heating methods. The present contribution aims at illustrating the advantages of this technology in homogeneous catalysis by ruthenium complexes and, when data are available, at comparing microwave-heated and conventionally heated experiments. Selected examples refer to olefin metathesis, isomerization reactions, 1,3-dipolar cycloadditions, atom transfer radical reactions, transfer hydrogenation reactions, and H/D exchange reactions. [less ▲]

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See detailHomobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies
Sauvage, Xavier ULg; Borguet, Yannick ULg; Zaragoza, Guillermo et al

in Advanced Synthesis & Catalysis (2009), 351(3), 441-455

Four homobimetallic ruthenium-(p-cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade ... [more ▼]

Four homobimetallic ruthenium-(p-cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade pathway from the ethylene complex [(p-cymene)Ru(mu-Cl)(3)RuCl(PCy3)(eta(2)-C2H4)] (7a). All the products were isolated and fully characterized by IR and NMR spectroscopies. The molecular structure of the indenylidene complex 11 was determined by X-ray crystallographic analysis. The catalytic activity of the four complexes was probed in various types of olefin metathesis reactions and compared with those of a related homobimetallic ruthenium-benzylidene complex, as well as first, second, and third generation monometallic Grubbs catalysts. In the ring-closing metathesis (RCM) of diethyl diallylmalonate, the homobimetallic ruthenium-indenylidene complex 11. outperformed all the ruthenium-benzylidene complexes under investigation and was only slightly less efficient than its monometallic parent. Cross-metathesis experiments with ethylene showed that deactivation of ruthenium-benzylidene or indenylidene complexes was due to the rapid bimolecular decomposition of methylidene active species into ethylene complex 7a. Vinylidene and allenylidene complexes were far less efficient catalyst precursors for ring-opening metathesis polymerization (ROMP) or RCM and remained inert under an ethylene atmosphere. Their catalytic activity was, however, substantially enhanced upon addition of an acidic co-catalyst that most likely promoted their in situ transformation into indenylidene species. Due to its straightforward synthesis and high metathetical activity, homobimetallic ruthenium-indenylidene complex 11 is a valuable intermediate for the preparation of the Hoveyda-Grubbs catalyst [Cl2Ru(PCy3)(=CH-o-O-i-PrC6H4)] via stoichiometric cross-metathesis with 2-isopropoxystyrene. ne procedure did not require any sacrificial phosphine and the transition metal not incorporated into the final product was easily recovered and recycled at the end of the process. [less ▲]

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See detailImidazol(in)ium-2-carboxylates as N-heterocyclic carbene precursors for the synthesis of second generation ruthenium metathesis catalysts
Sauvage, Xavier ULg; Demonceau, Albert ULg; Delaude, Lionel ULg

in Advanced Synthesis & Catalysis (2009), 351(11-12), 2031-2038

Five well-known ruthenium-N-heterocyclic carbene (NHC) catalysts for olefin metathesis and related reactions, including the second generation Grubbs and Hoveyda-Grubbs catalysts, were prepared by ... [more ▼]

Five well-known ruthenium-N-heterocyclic carbene (NHC) catalysts for olefin metathesis and related reactions, including the second generation Grubbs and Hoveyda-Grubbs catalysts, were prepared by phosphane exchange between first generation ruthenium-benzylidene or indenylidene complexes and NHCs generated in situ upon thermolysis of imidazol(in)ium-2-carboxylates. Because N-heterocyclic carbene -carbon dioxide adducts (NHC · CO2) are stable zwitterionic compounds that can be stored and handled with no particular precautions, this procedure is particularly attractive from a practical point of view. Reaction courses were conveniently monitored by 31P NMR spectroscopy and the experimental conditions were carefully adjusted to obtain high yields of pure products within short periods of time. [less ▲]

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See detailSynthesis and Catalytic Evaluation of Ruthenium-Arene Complexes Generated Using Imidazol(in)ium-2-carboxylates and Dithiocarboxylates
Delaude, Lionel ULg; Sauvage, Xavier ULg; Demonceau, Albert ULg et al

in Organometallics (2009), 28

The ability of five imidazol(in)ium-2-carboxylates and dithiocarboxylates bearing cyclohexyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms to act as NHC precursors for in situ ... [more ▼]

The ability of five imidazol(in)ium-2-carboxylates and dithiocarboxylates bearing cyclohexyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms to act as NHC precursors for in situ catalytic applications was probed in ruthenium-promoted ring-opening metathesis and atom transfer radical polymerizations. Results obtained with 1:2 mixtures of [RuCl2(p-cymene)]2 and NHC•CO2 adducts were in line with those reported previously starting from preformed [RuCl2(p-cymene)(NHC)] complexes, whereas the NHC•CS2 zwitterions were almost completely inactive. To account for this dichotomy, the preparation of preformed ruthenium‚àíarene complexes from [RuCl2(p-cymene)]2 and NHC•CX2 inner salts was thoroughly investigated. As expected, imidazolium-2-carboxylates lost their CO2 moiety and afforded [RuCl2(p-cymene)(NHC)] complexes in high yields, whereas the NHC•CS2 betaines retained their zwitterionic nature and led to cationic complexes of the [RuCl(p-cymene)(NHC•CS2)]PF6 type. These stable, 18-electron species are the first examples of well-defined transition-metal complexes bearing chelating NHC•CS2 ligands. They were characterized by various analytical techniques, and the molecular structure of [RuCl(p-cymene)(IMes•CS2)]PF6 was determined by X-ray diffraction analysis. [less ▲]

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See detailATRP of methyl methacrylate and styrene catalysed by homobimetallic ruthenium-vinylidene complexes
Bicchielli, Dario ULg; Borguet, Yannick ULg; Sauvage, Xavier ULg et al

in Polymer Preprints (2008)

Styrene and Me methacrylate were subjected to atom transfer radical polymn. using a homobimetallic ruthenium-vinylidene complex (p-cymene)RuCl2/(PCy3)(styrylidene)RuCl2 as catalyst and Et 2 ... [more ▼]

Styrene and Me methacrylate were subjected to atom transfer radical polymn. using a homobimetallic ruthenium-vinylidene complex (p-cymene)RuCl2/(PCy3)(styrylidene)RuCl2 as catalyst and Et 2-bromoisobutyrate (EBiB), 1-phenylethyl bromide, or CCl4 as initiators (in toluene). The polymns. proceeded in a controlled fashion and the polydispersities were quite narrow. Using (EBiB), an induction period was obsd. The polymn. of styrene ceased after 80% conversion because of the degrdn. of the complex into inactive species. With both monomers and CCl4 as initiator, the mol. wt. of the polymers was lower than the calcd. value, i.e., the initiation efficiency was >1. [less ▲]

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See detailThe Synthesis of N-Benzyl-2-azanorbornene via Aqueous Hetero Diels-Alder Reaction
Sauvage, Xavier ULg; Delaude, Lionel ULg

in Journal of Chemical Education (2008), 85(11), 1538-1540

The synthesis of N-benzyl-2-azanorbornene via aqueous hetero Diels-Alder reaction of cyclopentadiene and benzyliminium chloride formed in situ from benzylamine hydrochloride and formaldehyde is described ... [more ▼]

The synthesis of N-benzyl-2-azanorbornene via aqueous hetero Diels-Alder reaction of cyclopentadiene and benzyliminium chloride formed in situ from benzylamine hydrochloride and formaldehyde is described. Characterization of the product was achieved by IR and NMR spectroscopies. The spectral data acquired are thoroughly discussed. Numerous coupling constants were extracted from the 1H NMR spectrum. They provide a valuable material to familiarize students with the different types of proton-proton coupling patterns and their typical ranges. Karplus type correlations served to calculate 3J vicinal coupling constants as a function of dihedral angles. These computational studies involved molecular modeling. Because the synthetic part is rather straightforward and easy to carry out, this experiment is suitable for an introductory laboratory course where it can serve to illustrate the concepts of green chemistry and atom efficiency. Emphasis can also be placed on structural analysis for use within a spectroscopy course even if there is no activity component associated with it. Last but not least, the whole project provides ample materials for an advanced undergraduate laboratory in green chemistry that combines organic synthesis, structural analysis, and theoretical calculations. [less ▲]

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See detailATRP of methyl methacrylate catalysed by novel homo- and heterobimetallic ruthenium complexes
Borguet, Yannick ULg; Delfosse, Sebastien; Sauvage, Xavier ULg et al

in Polymer Preprints (2008), 49(2), 24-25

The atom transfer radical polymn. of Me methacrylate was studied in the presence of 6 novel homo- and heterobimetallic Ru complexes: (p-cymene)RuCl2/(PCy3)(ethylene)RuCl2, (p-cymene)RuCl2/(1,3-Mes2-4,5-X2 ... [more ▼]

The atom transfer radical polymn. of Me methacrylate was studied in the presence of 6 novel homo- and heterobimetallic Ru complexes: (p-cymene)RuCl2/(PCy3)(ethylene)RuCl2, (p-cymene)RuCl2/(1,3-Mes2-4,5-X2-imidazolin-2-ylidene)(ethylene)RuCl2 (X = H or Cl, Mes = 2,4,6-trimethylphenyl), and (p-cymene)RuCl2/[(2-dicyclohexylphosphinoethyl)cyclopentadienyl](Cp)TiX2 (X = F, Cl, or OBz). Et 2-bromoisobutyrate was used as initiator in all expts. All catalysts showed high efficiency in controlled synthesis of poly(Me methacrylate). Using the ruthenium/titanocene dibenzoate complex, the polymn. stopped after a few hours of reaction, affording nevertheless a polymer with a decent polydispersity. [less ▲]

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See detailHomobimetallic ruthenium-N-heterocyclic carbene complexes: Synthesis, characterization, and catalytic applications
Sauvage, Xavier ULg; Borguet, Yannick ULg; Noels, Alfred ULg et al

in Advanced Synthesis & Catalysis (2007), 349(1-2), 255-265

Two new homobimetallic ruthenium-arene complexes [(p-cymene)Ru(mu-Cl)(3)RuCl(eta(2)-C2H4)(L)], where L=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (3a) or 1,3-bis(2,4,6-trimethylphenyl)-4,5 ... [more ▼]

Two new homobimetallic ruthenium-arene complexes [(p-cymene)Ru(mu-Cl)(3)RuCl(eta(2)-C2H4)(L)], where L=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (3a) or 1,3-bis(2,4,6-trimethylphenyl)-4,5-dichloroimidazolin-2-ylidene (3b), were isolated in high yields upon heating a toluene solution of [RuCl2 (p-cymene)](2) with 1 equivalent of carbene ligand under an ethylene atmosphere. They were characterized by NMR and TGA. Their catalytic activity was investigated in the atom transfer radical polymerization of vinyl monomers. In the polymerization of methyl methacrylate, complex 3a displayed faster reaction rates than 3b and the related phosphine-based complex 2a (L=tricyclohexylphosphine), although control was more effective with the latter catalyst. When n-butyl acrylate or styrene served as monomer, a major shift of reactivity was observed between complex 2a that promoted controlled radical polymerization, and complexes 3a or 3b that favored metathetical coupling. Further homocoupling experiments with various styrene derivatives confirmed the outstanding aptitude of complex 3a (and to a lesser extent of 3b) to catalyze olefin metathesis reactions. Contrary to monometallic ruthenium-arene complexes of the [RuCl2(p-cymene)(L)] type, the new homobimetallic species did not require the addition of a diazo compound or visible light illumination to initiate the ring-opening metathesis of norbornene or cyclooctene. When alpha,omega-dienes were exposed to 3a or 3b, a mixture of cycloisomerization and ring-closing metathesis products was obtained in a non-selective way. Addition of a terminal alkyne co-catalyst enhanced the metathetical activity while completely repressing the cycloisomerization process. Thus, quantitative conversions of diethyl 2,2-diallylmalonate and N,N-diallyltosylamide were achieved within 2 h at room temperature using 2 mol % of catalyst precursor 3 a and 6 mol % of phenylacetylene. [less ▲]

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See detailHomobimetallic ruthenium-N-heterocyclic carbene complexes for olefin metathesis
Sauvage, Xavier ULg; Demonceau, Albert ULg; Delaude, Lionel ULg

in Imamoglu, Yavuz; Dragutan, Valerian (Eds.) Metathesis Chemistry. From nanostructure design to synthesis of advanced materials (2007)

In this chapter, the synthesis and catalytic activity towards olefin metathesis of homobimetallic ruthenium (Ru)-alkylidene, -cyclodiene or -arene complexes bearing phosphine or N-heterocyclic carbene ... [more ▼]

In this chapter, the synthesis and catalytic activity towards olefin metathesis of homobimetallic ruthenium (Ru)-alkylidene, -cyclodiene or -arene complexes bearing phosphine or N-heterocyclic carbene (NHC) ligands are reviewed. Emphasis is placed on the last category of bimetallic compds. Three representatives of this new type of mol. scaffold were investigated. Thus, [(p-cymene)Ru(m-Cl)3RuCl (h2-C2H4)(L)] complexes with L = PCy3 (15a), IMes (16a), or IMesCl2 (16b) were prepd. They served as catalyst precursors for cross-metathesis (CM) of various styrene derivs. These expts. revealed the outstanding aptitude of complex 16a (and to a lesser extent of 16b) to catalyze olefin metathesis reactions. Contrary to monometallic Ru-arene complexes of the [RuCl2(p-cymene)(L)] type, the new homobimetallic species did not require the addn. of a diazo compd. nor visible light illumination to initiate the ring-opening metathesis of norbornene or cyclo-octene. When di-Et 2,2-diallylmalonate and N,N-diallyltosylamide were exposed to 16a,b, a mixt. of cycloisomerization and ring-closing metathesis (RCM) products was obtained in a nonselective way. Addn. of phenylacetylene enhanced the metathetical activity while completely repressing the cycloisomerization process. [less ▲]

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See detailSynthesis of stilbenoids via the Suzuki-Miyaura reaction catalysed by palladium N-heterocyclic carbene complexes
Tudose, Adriana; Maj, Anna M.; Sauvage, Xavier ULg et al

in Journal of Molecular Catalysis A: Chemical (2006), 257(1-2), 158-166

The Suzuki-Miyaura reaction of aryl halides with trans-2-phenylvinylboronic acid using a series of related in situ generated N-heterocyclic carbene palladium(II) complexes was studied in order to evaluate ... [more ▼]

The Suzuki-Miyaura reaction of aryl halides with trans-2-phenylvinylboronic acid using a series of related in situ generated N-heterocyclic carbene palladium(II) complexes was studied in order to evaluate the effect of ligand structure and electronics on the catalytic activity and to investigate the nature of the catalyst species. The nature of the substituents of the carbene ligand was found to be critical. Specifically, the presence of alkyl groups on the ortho positions of the phenyl substituents was a requisite for obtaining the most efficient catalyst systems. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailMétathèse des oléfines et réactions radicalaires catalysées par des complexes ruthénium-carbène N-hétérocycliques
Demonceau, Albert ULg; Delfosse, Sébastien; Richel, Aurore ULg et al

Scientific conference (2005, November)

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See detailCatalytic applications of transition metal N-heterocyclic carbene complexes bearing nitrogen-containing substituents
Sauvage, Xavier ULg; Tudose, Adriana; Delfosse, Sébastien et al

Poster (2005)

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See detailCatalytic applications of transition metal N-heterocyclic carbene complexes bearing nitrogen-containing substituents
Sauvage, Xavier ULg; Tudose, Adriana; Delfosse, Sébastien et al

Conference (2005)

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See detailNew ruthenium catalysts bearing N-heterocyclic carbene ligands for ATRP
Sauvage, Xavier ULg; Richel, Aurore ULg; Delfosse, Sébastien et al

Poster (2003, May)

Stable nucleophilic N-heterocyclic carbenes (NHCs) are neutral, two-electron ligands with a negligible p-back-bonding tendency. They behave as phosphine mimics, yet they are better s- donors and they form ... [more ▼]

Stable nucleophilic N-heterocyclic carbenes (NHCs) are neutral, two-electron ligands with a negligible p-back-bonding tendency. They behave as phosphine mimics, yet they are better s- donors and they form stronger bonds to metal centers than most phosphines. Their electronic and steric properties are liable to ample modification simply by varying the substituents on the nitrogen atoms. Therefore, NHCs constitute a promising new class of ligands available for catalyst engineering and fine-tuning. We found that the 18-electron complex RuCl2(p-cymene)(PCy3) was a versatile and efficient promoter for ring-opening metathesis polymerization of both strained and low-strain cyclic olefins when activated by a suitable precursor such as trimethylsilyldiazomethane. This complex was also an excellent catalyst for ATRP (Atom Transfer Radical Polymerization) of MMA and styrene. In this poster, we present preliminary results obtained in olefin metathesis and in radical reactions (ATRP and Kharasch addition) when tricyclohexylphosphine was substituted by an N-heterocylic carbene ligand. [less ▲]

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See detailNew ruthenium catalysts bearing N-heterocyclic carbene ligands for ATRA and ATRP
Sauvage, Xavier ULg; Richel, Aurore ULg; Delfosse, Sébastien et al

in e-polymers (2003)

This study provides a glimpse of the synthetic possibilities arising from the use of NHC􀀀 s complexes in radical reactions, and illustrates how the fine tuning of the steric and electronic parameters of ... [more ▼]

This study provides a glimpse of the synthetic possibilities arising from the use of NHC􀀀 s complexes in radical reactions, and illustrates how the fine tuning of the steric and electronic parameters of this class of ruthenium complexes affect their catalytic activity. [less ▲]

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