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See detailNew tripodal iminophosphorane-based ethylene oligomerization catalysts - Part II. Catalytic behavior
Beaufort, Laurence; Benvenuti, Federica; Delaude, Lionel ULg et al

in Journal of Molecular Catalysis A : Chemistry (2008), 283(1-2), 77-82

Seven transition-metal complexes of general formula RC(CH2NPR'(3))(3))MX2 based on new tripodal iminophosphorane ligands were investigated as initiators for the oligomerization of ethylene in the presence ... [more ▼]

Seven transition-metal complexes of general formula RC(CH2NPR'(3))(3))MX2 based on new tripodal iminophosphorane ligands were investigated as initiators for the oligomerization of ethylene in the presence of aluminum co-catalysts using high-throughput techniques. In all cases, ethylene consumption peaked at ca. 30 degrees C and was not drastically affected by varying the nature of the metal (M = Ni, Fe, Pd, Cu), the aluminum co-catalyst (MMAO, Et2AlCl, or EtAlCl2) or the substituents of the tris(iminophosphorane) ligand (R = Me, Ph; R'= cyclopentyl, Ph). Structural modifications of the organometallic complexes, either at the metal center or within the tripodal ligand, however, had a significant impact on the oligomer distribution obtained. In particular, Pd-based catalyst (PhC(CH2NPPh3)(3))PdCl2 displayed an excellent selectivity toward hexene formation. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailN-heterocyclic carbene ruthenium complexes: Synthesis and catalytic properties
Dragutan, Ileana; Dragutan, Valerian; Delaude, Lionel ULg et al

in Revue Roumaine de Chimie (2007), 52(11), 1013-1025

Synthesis of imidazol(in)-2-ylidene ruthenium complexes relevant for metathesis and related catalytic processes is described. As an attractive alternative of importance for practical applications, the in ... [more ▼]

Synthesis of imidazol(in)-2-ylidene ruthenium complexes relevant for metathesis and related catalytic processes is described. As an attractive alternative of importance for practical applications, the in situ generation of new NHC ruthenium precatalysts, starting from the easily accessible imidazolium and imidazolinium salts, ruthenium dimer [RuCl2(p-cymene)](2) and a base, is reported in detail. The new NHC family of ruthenium complexes offers great promise as metathesis precatalysts enjoying a wide application profile in organic and polymer synthesis. [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 detailSynthesis of N-heterocyclic carbene precursors bearing biphenyl units and their use in ruthenium-catalyzed ring-opening metathesis polymerization
Maj, Anna M.; Delaude, Lionel ULg; Demonceau, Albert ULg et al

in Journal of Organometallic Chemistry (2007), 692(14), 3048-3056

A range of new imidazolium and imidazolinium chlorides bearing biphenyl units on their nitrogen atoms was synthesized. They differed by the electron-withdrawing or -donating nature and the steric bulk of ... [more ▼]

A range of new imidazolium and imidazolinium chlorides bearing biphenyl units on their nitrogen atoms was synthesized. They differed by the electron-withdrawing or -donating nature and the steric bulk of the substituents on their aromatic rings. These various N-heterocyclic carbene (NHC) precursors were combined with the [RuCl2(p-cymene)](2) dimer and potassium tert-butoxide to generate the corresponding ruthenium-arene complexes [RuCl2(p-cymene)(NHC)] in situ. The catalytic activity of these species was investigated in the photoinduced ring-opening metathesis polymerization (ROMP) of cyclooctene. The results obtained confirmed the necessity of blocking the ortho-positions of the phenyl rings in the vicinity of the metal center in order to attain high catalytic efficiencies. They also showed that changing the steric and electronic properties of the substituents on the remote phenyl rings of the biphenyl units had no significant influence on the outcome of the polymerization. (C) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailSynthesis of biphenylamines via Suzuki-Miyaura cross-coupling reactions
Maj, Anna M.; Delaude, Lionel ULg; Demonceau, Albert ULg et al

in Tetrahedron (2007), 63(12), 2657-2663

A small library of meta- and para-biphenylamines substituted by various alkyl, alkoxy, phenoxy, or halogeno groups on their aromatic rings was synthesized via Suzuki-Miyaura cross-coupling between ... [more ▼]

A small library of meta- and para-biphenylamines substituted by various alkyl, alkoxy, phenoxy, or halogeno groups on their aromatic rings was synthesized via Suzuki-Miyaura cross-coupling between bromoanilines and arylboronic acids using palladium catalysts. The experimental conditions were carefully adjusted to accommodate a wide range of substituents, in terms of electron-withdrawing or -donating ability and steric bulk. In some cases, protection and deprotection of the amine function via its trifluoroacetamide were added to the reaction sequence in order to facilitate the cross-coupling step. (c) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailA new tripodal ligand system based on the iminophosphorane functional group. Part 1: Synthesis and characterization
Beaufort, Laurence; Delaude, Lionel ULg; Noels, Alfred ULg

in Tetrahedron (2007), 63(30), 7003-7008

Two tripodal alcohols, viz., 1,1,1-tris(hydroxymethyl) ethane and alpha, alpha, alpha-tris(hydroxymethyl) toluene were converted by an efficient multi-step pathway involving azide formation into the ... [more ▼]

Two tripodal alcohols, viz., 1,1,1-tris(hydroxymethyl) ethane and alpha, alpha, alpha-tris(hydroxymethyl) toluene were converted by an efficient multi-step pathway involving azide formation into the corresponding tris(iminophosphorane) scaffolds bearing cyclopentyl (Cp) or phenyl groups on their phosphorus atoms, R-C(CH2-N] PR'(3))(3) (R Me or Ph, R'=Cp or Ph). The synthesis of some representative transition-metal complexes of Cu(I), Cu(II), Ni(II), and Pd(II) bearing these new tridentate ligands is also reported. (C) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailMetathesis
Delaude, Lionel ULg; Noels, Alfred ULg

in Seidel, A. (Ed.) Kirk-Othmer encyclopedia of chemical technology (2007)

A review. The scope of the reaction, theory and industrial application of alkene metathesis, including initiators and catalysts are described. Metathesis polymn. to polyolefins, alkyne metathesis, and ene ... [more ▼]

A review. The scope of the reaction, theory and industrial application of alkene metathesis, including initiators and catalysts are described. Metathesis polymn. to polyolefins, alkyne metathesis, and ene-yne metathesis are also considered. [less ▲]

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See detailSynthesis and application of new N-heterocyclic carbene ruthenium complexes in catalysis: A case study
Delaude, Lionel ULg; Demonceau, Albert ULg; Noels, Alfred ULg

in Current Organic Chemistry (2006), 10(2), 203-215

New imidazolium and imidazolinium salts were synthesized and their ability to act as stable N-heterocyclic carbene (NHC) ligand precursors was investigated in various ruthenium-catalyzed processes. Thus ... [more ▼]

New imidazolium and imidazolinium salts were synthesized and their ability to act as stable N-heterocyclic carbene (NHC) ligand precursors was investigated in various ruthenium-catalyzed processes. Thus, 1,3-diarylimidazol(in)ium chlorides bearing the phenyl, 1-naphthyl, 4-biphenyl, 3,5-dimethylphenyl, 2-tolyl, 2,6-dimethylphenyl, 2,4,6-trimethylphenyl (mesityl), and 2,6-diisopropylphenyl substituents were prepared. They were combined with the [RuCl2(p-cymene)](2) dimer and potassium tert-butoxide or sodium hydride to generate the corresponding ruthenium-arene complexes [RuCl2(p-cymene)(NHC)] in situ. The catalytic activity of all these species was investigated in the photoinduced ring-opening metathesis polymerization (ROMP) of norbornene and cyclooctene. Results from this study showed that the C4-C5 double bond in the imidazole ring of the NHC ligands was not crucial to achieve high catalytic efficiencies. The presence or the absence of alkyl groups on the ortho positions of the phenyl rings had a more pronounced influence. Blocking all the ortho positions was a requisite for obtaining efficient catalysts. Failure to do so probably resulted in the ortho-metallation of the carbene ligand, thereby altering the coordination sphere of the ruthenium active centers. Catalytic screenings were also carried out with the various imidazol(in)ium salts to evaluate their ability at promoting the cyclopropanation of styrene and cyclooctene with ethyl diazoacetate. Under the experimental conditions adopted, the exact nature of the N,N'-diaryl groups had very little influence on the outcome of these reactions. The imidazolium salts were further probed as catalyst modifiers for the Atom Transfer Radical Addition (ATRA) of carbon tetrachloride to styrene. Some species displayed a dual activity and promoted both olefin metathesis and ATRA. [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 detailElectrochemistry as a correlation tool with the catalytic activities in [RuCl2(p-cymene)(PAr3)]-catalysed Kharasch additions
Richel, Aurore ULg; Demonceau, Albert ULg; Noels, Alfred ULg

in Tetrahedron Letters (2006), 47

[RuCl2(p-cymene)] complexes containing triarylphosphine ligands with various substituents at the para position were used to catalyse the atom transfer radical addition of carbon tetrachloride to various ... [more ▼]

[RuCl2(p-cymene)] complexes containing triarylphosphine ligands with various substituents at the para position were used to catalyse the atom transfer radical addition of carbon tetrachloride to various olefins, and their catalytic activities were nicely correlated with their electrochemical parameters. [less ▲]

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See detailThe step-by-step Robinson annulation of chalcone and ethyl acetoacetate - An advanced undergraduate project in organic synthesis and structural analysis
Delaude, Lionel ULg; Grandjean, Jean ULg; Noels, Alfred ULg

in Journal of Chemical Education (2006), 83(8), 1225-1228

The Robinson annulation is a three-step process involving a Michael addition followed by an internal aldol condensation and a dehydration. Under appropriate experimental conditions, it is possible to stop ... [more ▼]

The Robinson annulation is a three-step process involving a Michael addition followed by an internal aldol condensation and a dehydration. Under appropriate experimental conditions, it is possible to stop the reaction after every step and to isolate the three products separately. This feature is particularly attractive in the frame of an organic chemistry course. It allows students to confirm experimentally the validity of the stepwise mechanism and to get a more thorough understanding of the whole process. It also permits them to synthesize a rich set of related molecules that can be compared and characterized through various analytical techniques. Thus, a stoichiometric mixture of chalcone and ethyl acetoacetate was reacted in ethanol. Depending on the quantity of barium hydroxide monohydrate used as catalyst, the reaction time, and the temperature, three different products were obtained. Their full IR, 1H, 13C, COSY, NOESY, and HETCOR NMR spectra are supplied. Examination of the spectroscopic data helps uncover many challenging structural analysis problems. Among them, the diastereoselective formation of chiral centers during the annulation process, the distinction between axial and equatorial substituents on a cyclohexane ring, and the possibility of a keto-enol tautomerism are extensively discussed. [less ▲]

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See detailControlled radical polymerization of vinyl monomers catalyzed by ruthenium N-heterocyclic carbene complexes
Delfosse, Sébastien; Richel, Aurore ULg; Delaude, Lionel ULg et al

in Matyjaszewski, K. (Ed.) Progress in Controlled/Living Radical Polymerization / ACS Symposium Series 944 (2006)

The relative catalytic activities of a series of ruthenium-based complexes of the general formula [RuCl2(p-cymene)(NHC)], [RuCl2(=CHPh)(PR3)(NHC)] and [RuCl2(=CHPh)(NHC)2] (NHC is a N-heterocyclic carbene ... [more ▼]

The relative catalytic activities of a series of ruthenium-based complexes of the general formula [RuCl2(p-cymene)(NHC)], [RuCl2(=CHPh)(PR3)(NHC)] and [RuCl2(=CHPh)(NHC)2] (NHC is a N-heterocyclic carbene ligand) were determined by investigating the atom transfer radical polymerization (ATRP) of methyl mathacrylate and styrene. The catalytic activity of a variety of related [RuCl(O^N)(=CHR)(NHC)] complexes and their cationic couterparts, [Ru(O^N)(=CHR)(NHC)]+BF4- (R = Ph or OEt, O^N is a Schiff base ligand), is also reported. The results clearly demonstrate that, with both methyl methacrylate and styrene, subtle modifications of the substituents of the NHC ligand lead to dramatic changes in the ability of the resulting ruthenium complexes to favor the occurence of a well-behaved ATRP. [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 detailMicrowave-assisted ruthenium-catalysed atom transfer radical reactions
Delfosse, Sébastien; Richel, Aurore ULg; Wei, H. et al

Poster (2005, August)

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See detailOlefin cyclopropanation and insertion into O-H bonds mediated by copper(I) and palladium(II) covalently anchored to silica xerogels
Sacco, Luigi; Lambert, Stéphanie ULg; Pirard, Jean-Paul ULg et al

in Journal of Catalysis (2005), 232(1), 51-59

Copper(I) and palladium(II) ligated to pyrazolylpyridine hearing a tethered (trimethoxysilyl)propyl group in position 4 of the pyrazole ring were chemically bonded to silica via a sol-gel process. The ... [more ▼]

Copper(I) and palladium(II) ligated to pyrazolylpyridine hearing a tethered (trimethoxysilyl)propyl group in position 4 of the pyrazole ring were chemically bonded to silica via a sol-gel process. The textural properties of the materials (Specific Surface area, porous volume, and pore size distribution) were characterized by nitrogen adsorption-desorption isotherms, mercury porosimetry, and TEM analysis. The hybrid materials were tested as catalysts in olefin cyclopropanation and as potential chemoselective catalysts in the reaction with unsaturated alcohols (double bond versus -OH group), with ethyl diazoacetate as a carbene precursor, and compared with the corresponding homogeneous complexes. © 2005 Elsevier Inc. All rights reserved. [less ▲]

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See detailMicrowave-Enhanced Ruthenium Catalysed Atom Transfer Radical Additions
Richel, Aurore ULg; Leclerc, Alain; Demonceau, Albert ULg et al

Poster (2005)

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