References of "Demonceau, Albert"
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See detailOlefin metathesis reactions state of the art and outlook
Demonceau, Albert ULg; Delaude, Lionel ULg

in Chimica Oggi = Chemistry Today (2007), 25(5, SEP-OCT), 65-68

Olefin metathesis is a metal-catalysed organic reaction, which involves the statistical redistribution of carbon-carbon double bonds. Since its discovery in the 1950's, this transformation has gained ... [more ▼]

Olefin metathesis is a metal-catalysed organic reaction, which involves the statistical redistribution of carbon-carbon double bonds. Since its discovery in the 1950's, this transformation has gained widespread use in research laboratories and industry for making products ranging, from drugs and polymers to enhanced fuels. Its advantages include the ability to build up complex structural scaffolds with remarkable atom economy. Major industrial processes usually rely on inexpensive, ill-defined, multicomponent catalytic systems, while research laboratory applications take advantage of well-defined metal alkylidene complexes of molybdenum and ruthenium that combine high activities and ease of set-up under reproducible conditions, albeit at the price of a higher cost. [less ▲]

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See detailSingle-mode microwave-assisted atom transfer radical polymerization catalyzed by [RuCl2(p-cymene)(PCy3)]
Delfosse, Sebastien; Borguet, Yannick ULg; Delaude, Lionel ULg et al

in Macromolecular Rapid Communications (2007), 28(4), 492-503

In the atom transfer radical polymerization (ATRP) of methyl methacrylate in the presence of [RuCl2(p-cymene)(PCy3)] (p-cymene=4-isopropyltoluene, PCy3=tricyclohexylphosphine), a microwave effect is noted ... [more ▼]

In the atom transfer radical polymerization (ATRP) of methyl methacrylate in the presence of [RuCl2(p-cymene)(PCy3)] (p-cymene=4-isopropyltoluene, PCy3=tricyclohexylphosphine), a microwave effect is noted which strikingly depends on both the temperature and the method used (conventional microwave synthesis (CMS, i.e., without simultaneous cooling) or enhanced microwave synthesis (EMS, with simultaneous cooling)). Thus, between 85 and 120 degrees C under CMS conditions, microwave-assisted polymerizations take place in a controlled fashion, and at 120 degrees C the microwave-assisted polymerization is three times faster than the conventionally heated protocol. However, from 130 degrees C, microwave irradiation has a deleterious effect and the polymerizations are no longer controlled. Likewise, using the EMS method in the temperature range of 85-120 degrees C results in uncontrolled processes, as indicated by the unsuccessful resumption of the polymerizations. These failures might be attributed to a significantly high concentration of radical species, which results in enhanced propagation and termination - mostly disproportionation - rates. [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 detailMicrowave-enhanced ruthenium-catalysed atom transfer radical additions
Borguet, Yannick ULg; Richel, Aurore ULg; Delfosse, Sbastien et al

in Tetrahedron Letters (2007), 48(36), 6334-6338

The first monomode microwave-assisted atom transfer radical additions (ATRA) of carbon tetrachloride to various olefins were successfully performed, affording the adducts with almost quantitative yields ... [more ▼]

The first monomode microwave-assisted atom transfer radical additions (ATRA) of carbon tetrachloride to various olefins were successfully performed, affording the adducts with almost quantitative yields in less than 10 min at 160 'C. (c) 2007 Elsevier Ltd. All rights reserved. [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 detailNHC-Ru complexes- Friendly catalytic tools for manifold chemical transformations
Dragutan, Valerian; Dragutan, Ileana; Delaude, Lionel ULg et al

in Coordination Chemistry Reviews (2007), 251(5-6), 765-794

N-Heterocyclic carbenes are now commonly encountered in organometallic and inorganic coordination chemistry. The increasing attention they enjoy is due to their ability to act as ancillary ligands in a ... [more ▼]

N-Heterocyclic carbenes are now commonly encountered in organometallic and inorganic coordination chemistry. The increasing attention they enjoy is due to their ability to act as ancillary ligands in a growing number of transition metal catalysts or even to play the role of nucleophilic reagents and catalysts in diverse organic transformations. As a fine addition to the NHC-Ru-alkylidenes, popular for their tremendous success in metathesis chemistry, an array of robust and stable Ru-NHCs has proven their utility in non-metathetical reactions. The present review surveys different classes of Ru-NHCs and their applications as efficient catalysts (or precatalysts) in several types of fundamental organic processes e.g. hydrogenation, hydrogen transfer, isomerization, cycloisomerization, cyclopropanation, hydrosilylation, allylation and deallylation, enol-ester synthesis, heterocycle synthesis, C-C alkyne coupling, Kharasch addition and ATRP. A special section is devoted to tandem processes some of which include concurrent or sequential metathesis steps. Relevant mechanistic and stereochemical aspects related to NHC-Ru catalysis will be highlighted. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailOlefin metathesis with ruthenium-arene catalysts bearing N-heterocyclic carbene ligands
Delaude, Lionel ULg; Demonceau, Albert ULg

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

In this chapter, we summarize the main results of our investigations on the ring-opening metathesis polymn. (ROMP) of cyclooctene catalyzed by various ruthenium (Ru)-arene complexes bearing imidazolin-2 ... [more ▼]

In this chapter, we summarize the main results of our investigations on the ring-opening metathesis polymn. (ROMP) of cyclooctene catalyzed by various ruthenium (Ru)-arene complexes bearing imidazolin-2-ylidene, imidazolidin-2-ylidene, or triazolin-5-ylidene ligands. Three major findings emerged from this study. First, we underscored the intervention of a photochem. activation step due to visible light illumination. Second, we established that the presence of an endocyclic double bond in the carbene ligand central heterocycle was not crucial to achieve high catalytic efficiencies. Third, we demonstrated that ortho-metalation of the N-heterocyclic carbene (NHC) ligand by the Ru center led to inactive catalysts. [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 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 detailMicrowave-assisted synthesis of N-heterocyclic carbene precursors
Aidouni, Adila; Demonceau, Albert ULg; Delaude, Lionel ULg

in Synlett (2006), (3), 493-495

A very simple and efficient procedure is reported for the synthesis of 1,3-diarylimidazolinium chlorides by cyclization of N,N'-diarylethylenediamines dihydrochlorides with triethyl ortho-formate under ... [more ▼]

A very simple and efficient procedure is reported for the synthesis of 1,3-diarylimidazolinium chlorides by cyclization of N,N'-diarylethylenediamines dihydrochlorides with triethyl ortho-formate under microwave irradiation. [less ▲]

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See detailImidazol(in)ium-2-carboxylates as N-heterocyclic carbene precursors in ruthenium-arene catalysts for olefin metathesis and cyclopropanation
Tudose, Adriana; Demonceau, Albert ULg; Delaude, Lionel ULg

in Journal of Organometallic Chemistry (2006), 691(24-25), 5356-5365

Five imidazol(in)ium-2-carboxylates bearing cyclohexyl, mesityl, or 2,.6-diisopropylphenyl substituents on their nitrogen atoms were prepared from the corresponding N-heterocyclic carbenes (NHCs) by ... [more ▼]

Five imidazol(in)ium-2-carboxylates bearing cyclohexyl, mesityl, or 2,.6-diisopropylphenyl substituents on their nitrogen atoms were prepared from the corresponding N-heterocyclic carbenes (NHCs) by reaction with carbon dioxide. They were characterized by IR and NMR spectroscopies, and by TGA. Their ability to act as NHC precursors for in situ catalytic applications was probed in ruthenium-promoted olefin metathesis and cyclopropanation reactions. When visible light induced ring-opening metathesis polymerization of cyclooctene or cyclopropanation of styrene with ethyl diazoacetate were carried out at 60 degrees C in the presence of [RuCl2(p-cymene)](2), the NHC (.) CO2 adducts and their NHC (.) HX counterparts (X = Cl, BF4) displayed similar activities. When metathesis polymerizations were performed at room temperature, the carboxylates proved far superior to the corresponding imidazol(in)ium acid salts. They displayed the same level of activity as the preformed RuCl2(p-cymene)(IMes) complex, whereas the combination of NHC (.) HX and KO-t-Bu were almost totally inactive. Results obtained for cyclopropanation reactions at room temperature did not show such a large discrepancy of behavior between the two types of adducts. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailImidazol(in)ium carboxylates as N-heterocyclic carbene ligand precursors for Suzuki-Miyaura reactions
Tudose, Adriana; Delaude, Lionel ULg; André, Benoît et al

in Tetrahedron Letters (2006), 47(48), 8529-8533

Simple catalysts formed in situ from palladium acetate and a variety of imidazolium and imidazolinium carboxylates and dithiocarboxylates have been screened in the coupling of aryl halides with trans-2 ... [more ▼]

Simple catalysts formed in situ from palladium acetate and a variety of imidazolium and imidazolinium carboxylates and dithiocarboxylates have been screened in the coupling of aryl halides with trans-2-phenylvinylboronic acid. Imidazol(in)ium carboxylates show an excellent activity, which compares to that displayed by the parent imidazol(in)ium chlorides, whereas imidazol(in)ium dithiocarboxylates are poorly efficient. Interestingly, the base employed exerts a profound influence on the trans/cis stereochemistry of the coupling product. (c) 2006 Elsevier Ltd. All rights reserved. [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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