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See detailRuthenium-promoted radical processes toward fine chemistry
Delaude, Lionel ULg; Demonceau, Albert ULg; Noels, Alfred ULg

in Dixneuf, Pierre Henri; Bruneau, Christian (Eds.) Ruthenium catalysts and fine chemistry (2004)

A review. Ruthenium holds a prominent position among the many transition metals used in radical chem. The dichlorotris(triphenylphosphine) complex [RuCl2(PPh3)3] was the first active ruthenium-based ... [more ▼]

A review. Ruthenium holds a prominent position among the many transition metals used in radical chem. The dichlorotris(triphenylphosphine) complex [RuCl2(PPh3)3] was the first active ruthenium-based catalyst investigated for atom-transfer radical addn. processes and has found numerous applications in org. synthesis. Other catalytic systems that have been devised since include (1) neutral or cationic Grubbs-type complexes bearing an alkylidene fragment and either phosphine, N-heterocyclic carbene, or Schiff base ligands, (2) half-sandwich ruthenium complexes bearing a cyclopentadienyl, a pentamethylcyclopentadienyl, or an indenyl ligand, and (3) ruthenium complexes bearing anionic carborane-phosphine and dicarbollide ligands. Their activities are discussed and the predictive value of cyclic voltammetry in radical chem. is questioned. A related example of a ruthenium-catalyzed C-H hydroxylation reaction is also reported. [less ▲]

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See detailRuthenium N-heterocyclic carbene complexes: Versatile catalysts precursors for olefin metathesis, olefin cyclopropanation, and radical reactions
Demonceau, Albert ULg; Richel, Aurore ULg; Delfosse, Sébastien et al

Conference (2003, August)

N-heterocyclic carbenes are divalent carbon species, which are commonly used as neutral, two-electron ligands with a negligible p-back-bonding tendency. They behave as phosphine mimics, yet they are ... [more ▼]

N-heterocyclic carbenes are divalent carbon species, which are commonly used as 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 centres than most phosphines. Their electronic and steric properties are liable to ample modification simply by varying the substituents on the nitrogen atoms. Therefore, N-heterocyclic carbenes constitute a promising new class of ligands available for catalyst engineering and fine tuning, and a great deal of attention has been paid to them recently. We found that the 18-electron complex RuCl2(p-cymene)(PCy3) was a versatile and efficient promoter for the ring-opening metathesis polymerisation of both strained and low-strain cyclic olefins when activated by a suitable carbene precursor such as trimethylsilyl-diazomethane. RuCl2(p-cymene)(PCy3) was also an excellent catalyst for ATRP (Atom Transfer Radical Polymerisation) of methyl methacrylate and styrene. Here, we present preliminary results obtained in olefin metathesis, olefin cyclopropanation, and radical reactions (ATRP and Kharasch addition) when tricyclohexylphosphine was substituted by an N-heterocyclic ligand. [less ▲]

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See detailDual activity of ruthenium catalysts in controlled radical reactions and olefin metathesis
Delaude, Lionel ULg; Filmon, Karine; Delfosse, Sébastien et al

Conference (2003, May)

The catalytic activity of five ruthenium-arene complexes of the RuCl2(p-cymene)L type was investigated in controlled radical reactions and olefin metathesis. The ligands L were stable Nheterocyclic ... [more ▼]

The catalytic activity of five ruthenium-arene complexes of the RuCl2(p-cymene)L type was investigated in controlled radical reactions and olefin metathesis. The ligands L were stable Nheterocyclic carbenes (NHCs) derived from imidazol-2-ylidene. They differed by the nature of the substituents on the nitrogen atoms (R1) and on the carbon-carbon double bond (R2) of the heterocyclic ring. Thus, R1 was either the mesityl or the cyclohexyl group, and R2 included methyl, hydrogen, or chloro substituents.The complexes were tested as initiators for the Atom Transfer Radical Addition (ATRA) of carbon tetrachloride to methyl methacrylate and styrene, for the Atom Transfer Radical Polymerization (ATRP) of methyl methacrylate and styrene, and for the Ring-Opening Metathesis Polymerization (ROMP) of cyclooctene. Some species displayed a dual activity and promoted both olefin metathesis and ATRP. [less ▲]

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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 detailTuning of ruthenium N-heterocyclic carbene catalysts for ATRP
Delaude, Lionel ULg; Delfosse, Sébastien ULg; Richel, Aurore ULg et al

in Chemical Communications (2003), (13), 1526-1527

Depending on the substituents, R-1 and R-2, ruthenium(II) - p-cymene complexes bearing N-heterocyclic carbene ligands are either efficient catalysts for the well-controlled atom transfer radical ... [more ▼]

Depending on the substituents, R-1 and R-2, ruthenium(II) - p-cymene complexes bearing N-heterocyclic carbene ligands are either efficient catalysts for the well-controlled atom transfer radical polymerisation of methyl methacrylate and styrene, or promote a redox-initiated free-radical process. [less ▲]

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See detailRuthenium catalysts bearing N-heterocyclic carbene ligands in atom transfer radical reactions
Richel, Aurore ULg; Delfosse, Sébastien ULg; Cremasco, Cédric et al

in Tetrahedron Letters (2003), 44(32), 6011-6015

The catalytic activity of ruthenium-p-cymene complexes bearing N-heterocyclic carbene ligands in atom transfer radical addition (ATRA) or polymerisation (ATRP) strongly depends on the substituents of the ... [more ▼]

The catalytic activity of ruthenium-p-cymene complexes bearing N-heterocyclic carbene ligands in atom transfer radical addition (ATRA) or polymerisation (ATRP) strongly depends on the substituents of the carbene ligand, thereby providing a nice illustration of the importance of organometallic engineering and ligand fine tuning in homogeneous catalysis. (C) 2003 Elsevier Ltd. All rights reserved. [less ▲]

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See detailProbing the stereoselectivity of the ruthenium-catalyzed ring-opening metathesis polymerization of norbornene and norbornadiene diesters
Delaude, Lionel ULg; Demonceau, Albert ULg; Noels, Alfred ULg

in Macromolecules (2003), 36(5), 1446-1456

The ring-opening metathesis polymerization (ROMP) of two optically active 2,3-dicarboalkoxynorbornadienes derived from (S)-(-)-2-methyl-1-butanol and (R)-(-)-2-butanol were carried out in the presence of ... [more ▼]

The ring-opening metathesis polymerization (ROMP) of two optically active 2,3-dicarboalkoxynorbornadienes derived from (S)-(-)-2-methyl-1-butanol and (R)-(-)-2-butanol were carried out in the presence of the [RuCl2(P-cymene)](2) catalyst precursor activated by trimethylsilyldiazomethane (TMSD). H-1 and C-13 NMR analyses showed that a high degree of stereoregularity was achieved, and homonuclear proton-proton COSY spectroscopy indicated that the major trans fractions of the polymers were most likely isotactic, while the minor cis fractions were syndiotactic. Ring-opened metathesis polymers were also made from 2,3-dicarbomethoxynorbornadiene and exo,exo-2,3-dicarbomethoxy-5-norbornene. They were hydrogenated into the corresponding polynorbornanes using diimide. The NMR spectra of the reduced materials confirmed that the unsaturated parent polymers had an all-trans highly isotactic microstructure. A tentative mechanism involving arene loss, carbene formation, and monomer chelation is proposed to account for the observed stereoselectivities. [less ▲]

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See detailNew ruthenium catalysts bearing N-heterocyclic carbene ligands in Kharasch chemistry
Tudose, Adriana; Delfosse, Sébastien; Richel, Aurore ULg et al

Poster (2003)

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See detailTuning of rethenium N-heterocyclic carbene catalysts for olefin polymerisation and fine chemistry
Demonceau, Albert ULg; Richel, Aurore ULg; Delfosse, Sébastien et al

Scientific conference (2003)

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

in e-polymers (2003)

New ruthenium catalysts bearing N-heterocyclic carbene ligands in Kharasch chemistry

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See detailTuning of ruthenium N-heterocyclic carbene catalysts for olefin polymerisation and fine chemistry
Demonceau, Albert ULg; Delfosse, Sébastien; Richel, Aurore ULg et al

Scientific conference (2003)

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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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See detailDual activity of ruthenium catalysts in controlled radical reactions and olefin metathesis
Delaude, Lionel ULg; Delfosse, Sébastien; Richel, Aurore ULg et al

in Imamoglu, Yavuz; Bencze, Laszlo (Eds.) Novel metathesis chemistry: designing well-defined initiator systems for specialty chemical synthesis, tailored polymers and advanced material application (2003)

The catalytic activity of five ruthenium-arene complexes of the RuCl2(p-cymene)L type was investigated in controlled radical reactions and olefin metathesis. The ligands L were stable N-heterocyclic ... [more ▼]

The catalytic activity of five ruthenium-arene complexes of the RuCl2(p-cymene)L type was investigated in controlled radical reactions and olefin metathesis. The ligands L were stable N-heterocyclic carbenes (NHCs) derived from imidazol-2-ylidene. They differed by the nature of the substituents on the nitrogen atoms (R1) and on the carbon-carbon double bond (R2) of the heterocyclic ring. Thus, R1 was either the mesityl or the cyclohexyl group, and R2 included methyl, hydrogen, or chloro substituents. The complexes were tested as initators for the Atom Transfer Radical Addition (ATRA) of carbon tetrachloride to methyl methacrylate and styrene, for the Atom Transfer Radical Polymerization (ATRP) of methyl methacrylate and styrene, and for the Ring-Opening Metathesis Polymerization (ROMP) of cyclooctene. Some species displayed a dual activity and promoted both olefin metathesis and ATRP. [less ▲]

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See detailProbing the tacticity of ring-opened metathesis polymers of norbornene and norbornadiene diesters by NMR spectroscopy
Delaude, Lionel ULg; Demonceau, Albert ULg; Noels, Alfred ULg

in Bencze, Laszlo; Imamoglu, Yavuz (Eds.) Novel metathesis chemistry: designing well-defined initiator systems for specialty chemical synthesis, tailored polymers and advanced material application (2003)

This chapter summarizes the various NMR experiments that were applied to probe the main stereochemical features of polymers prepared by ring-opening metathesis polymerization (ROMP) of 2,3 ... [more ▼]

This chapter summarizes the various NMR experiments that were applied to probe the main stereochemical features of polymers prepared by ring-opening metathesis polymerization (ROMP) of 2,3-dicarboalkoxynorbornadienes and 2,3-dicarboalkoxynorbornenes catalyzed by the dichloro ruthenium arene dimer (RuCl2(p-cymene))2 in the presence of trimethylsilyldiazomethane (TMSD). Direct spectroscopic methods based on the examination of cross-coupling peaks in polymers derived from optically active monomers (1H COSY NMR) and indirect methods based on the analysis of the hydrogenated derivatives of unsaturated parent polyolefins (1H and 13C NMR) led to the same conclusion. They both showed that high trans, highly isotactic polymers were formed using the ruthenium-arene catalyst precursor. [less ▲]

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See detailNew in situ generated ruthenium catalysts bearing N-heterocyclic carbene ligands for the ring-opening metathesis polymerization of cyclooctene
Delaude, Lionel ULg; Szypa, Magdalena; Demonceau, Albert ULg et al

in Advanced Synthesis & Catalysis (2002), 344(6-7), 749-756

New 1,3-diarylimidazol(in)ium chlorides bearing phenyl, 1-naphthyl, 4-biphenyl, 2-tolyl, 2,6-dimethylphenyl, and 3,5-dimethylphenyl substituents were synthesized. They were combined with [RuCl2 (p-cymene ... [more ▼]

New 1,3-diarylimidazol(in)ium chlorides bearing phenyl, 1-naphthyl, 4-biphenyl, 2-tolyl, 2,6-dimethylphenyl, and 3,5-dimethylphenyl substituents were synthesized. They were combined with [RuCl2 (p-cymene)](2) and potassium tert-butoxide or sodium hydride to generate the corresponding ruthenium-N-heterocyclic carbene complexes in situ. Catalyst precursors derived from imidazol(in)ium salts bearing the 2,4,6-trimethylphenyl (mesityl) and the 2,6-diisopropylphenyl groups were also prepared. The catalytic activity of all these species in the photoinduced ring-opening metathesis polymerization of cyclooctene was investigated. The C4-C5 double bond in the imidazole ring of the N-heterocyclic carbene 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 results in the ortho-metallation of the carbene ligand, thereby altering the coordination sphere of the ruthenium active centers. [less ▲]

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See detailSynthesis and ring-opening metathesis polymerization of eight-membered unsaturated lactams and related monomers
Baran, Janusz; Bogdanska, Irena; Jan, Dominique et al

in Journal of Molecular Catalysis A-Chemical (2002), 190(1-févr Sp. Iss. SI), 109-116

Novel eight-membered ring unsaturated lactams were synthesized and tested as monomers for the ruthenium-catalyzed ring-opening metathesis polymerization (ROMP). The reaction of a N-protected cyclic ... [more ▼]

Novel eight-membered ring unsaturated lactams were synthesized and tested as monomers for the ruthenium-catalyzed ring-opening metathesis polymerization (ROMP). The reaction of a N-protected cyclic alkeneamine was also investigated. The Grubbs' benzylidene complexes RuCl2(=CHPh)(PCy3)(2) or RUCl2(=CHPh)(PCy3)(IMesH(2)) and selected ruthenium-arene species bearing either phosphine or stable Arduengo-type N-heterocyclic carbene ligands served as catalyst precursors. In most cases, isomerization of the starting materials took place and only 1-benzyl-1-aza-2-ketocyclooct-5-ene afforded a polymeric product. This polyamide was characterized by numerous analytical techniques. (C) 2002 Elsevier Science B.V All rights reserved. [less ▲]

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See detailVisible light induced ring-opening metathesis polymerisation of cyclooctene
Delaude, Lionel ULg; Demonceau, Albert ULg; Noels, Alfred ULg

in Chemical Communications (2001), (11), 986-987

Under visible light irradiation, ruthenium-arene complexes bearing N-heterocyclic carbene ligands with aryl substituents - either preformed or generated in situ - are active catalyst precursors for the ... [more ▼]

Under visible light irradiation, ruthenium-arene complexes bearing N-heterocyclic carbene ligands with aryl substituents - either preformed or generated in situ - are active catalyst precursors for the ROMP of cyclooctene already at room temperature. [less ▲]

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See detailEvaluation of ruthenium-based complexes for the controlled radical polymerization of vinyl monomers
Simal, François; Jan, Dominique; Delaude, Lionel ULg et al

in Canadian Journal of Chemistry (2001), 79(5-6), 529-535

New complexes of the type RuCl2(p-cymene)L where the ligand L is either a phosphine or a stable triazolinylidene carbene have been tested and compared to the Grubbs' benzylidene complex RuCl2(=CHPh)(PCy3 ... [more ▼]

New complexes of the type RuCl2(p-cymene)L where the ligand L is either a phosphine or a stable triazolinylidene carbene have been tested and compared to the Grubbs' benzylidene complex RuCl2(=CHPh)(PCy3)(2) as catalyst precursors for the controlled atom transfer radical polymerization (ATRP) of methyl methacrylate and of various para-substituted styrenes. Kinetic data and Hammett rho constants are reported, as well as the X-ray structure of the ortho-metallated triazolinylidene-ruthenium(II) complex RuCl(p-cymene)[1,2-phenylene[3,4-diphenyl-1H-1,2,4-triazol-1-yl-5(4H)-yl idene]]. [less ▲]

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