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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 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 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 detailFacile Microwave-Assisted Synthesis of Cyclic Amidinium Salts
Aidouni, Adila; Bendahou, Soufiane; Demonceau, Albert ULg et al

in Journal of Combinatorial Chemistry (2008), 10(6), 886-892

The cyclization of N,N '-dialkyl or diaryl ethane-1,2-diamines or propane-1,3-diamines with inorganic ammonium salts and orthoesters proceeds briskly under microwave irradiation to afford the ... [more ▼]

The cyclization of N,N '-dialkyl or diaryl ethane-1,2-diamines or propane-1,3-diamines with inorganic ammonium salts and orthoesters proceeds briskly under microwave irradiation to afford the corresponding imidazolinium or tetrahydropyrimidinium salts. The transformation is highly versatile and tolerates a wide range of substituents and counterions. It could be scaled from 1 to 50 mmol without any difficulty. Because the workup is equally rapid and straightforward, this experimental procedure provides fast and convenient access to an important class of heterocyclic compounds that have found numerous applications as N-heterocyclic carbene precursors, organocatalysts, and ionic liquids. [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 detailMicrowave-assisted synthesis of imidazolinium salts
Hans, Morgan; Demonceau, Albert ULg; Delaude, Lionel ULg

in Polymer Preprints (2008), 49(2), 942-943

Imidazolinium salts were prepd. via microwave-assisted cyclocondensation of ethanediamines with triethoxy alkanes or triethoxymethyl benzene. The synthesized imidazolinium salts may be used as NHC ... [more ▼]

Imidazolinium salts were prepd. via microwave-assisted cyclocondensation of ethanediamines with triethoxy alkanes or triethoxymethyl benzene. The synthesized imidazolinium salts may be used as NHC precursors or ionic liqs. [less ▲]

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See detailMicrowave-assisted synthesis of vinyl esters through ruthenium-catalyzed addition of carboxylic acids to alkynes
Nicks, Francois ULg; Libert, Lionel ULg; Delaude, Lionel ULg et al

in Polymer Preprints (2008), 49(2), 944-945

1-Hexen-2-yl 4-acetoxybenzoate was regioselectively prepd. via microwave-assisted ruthenium-catalyzed addn. of 4-acetoxybenzoic acid to 1-hexyne. Species of catalysts, reaction time and temp. play roles ... [more ▼]

1-Hexen-2-yl 4-acetoxybenzoate was regioselectively prepd. via microwave-assisted ruthenium-catalyzed addn. of 4-acetoxybenzoic acid to 1-hexyne. Species of catalysts, reaction time and temp. play roles in the reaction respect to yields and selectivity, therefore were examd. Microwave effect was obsd. and preferred to the generation of the Markovnikov-type product compared to traditional heating. [less ▲]

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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 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 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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