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See detailAtom Transfer Radical Polymerisation (ATRP) and Kharasch addition mediated by titanium-ruthenium bimetallic systems
Richel, Aurore ULg; Delfosse, Sébastien; Demonceau, Albert ULg et al

Poster (2003)

Numerous studies have been directed towards the synthesis of early-late heterobimetallic complexes. Surprisingly, only few reports have been reported about their catalytic behaviour. However, their ... [more ▼]

Numerous studies have been directed towards the synthesis of early-late heterobimetallic complexes. Surprisingly, only few reports have been reported about their catalytic behaviour. However, their potential in homogeneous catalysis is enormous. Indeed, a co-operative work by the two metal centres in the complex may lead to new catalytic systems with unique reactivity. <br /> <br />The Dijon’s team has concentrated their efforts on the synthesis and study of heterobimetallic complexes in which both metal fragments are known for their catalytic activity. Titanocenes are of considerable interest as catalysts for the polymerisation of a-olefins. The catalytic performance of RuCl2(arene) complexes (1) has been demonstrated in different reactions, including olefin metathesis and atom transfer radical polymerisation (ATRP). In attempts to examine such type of catalytic systems, complexation of bent titanocene metallo-ligands by the [RuCl2(p-cymene)]2 dimer is currently investigated. [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 detailControlled radical polymerization catalyzed by ruthenium complexes: Variations on Ru-Cp#
Delfosse, Sébastien; Richel, Aurore ULg; Simal, François et al

in Matyjaszewski, Krzysztof (Ed.) ADVANCES IN CONTROLLED/LIVING RADICAL POLYMERIZATION (2003)

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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 detailRuthenium alkylidenes: a new class of catalysts for Kharasch addition and controlled radical polymerisation of vinyl monomers
Delfosse, Sébastien; Richel, Aurore ULg; Demonceau, Albert ULg et al

in e-polymers (2003)

Air-stable and readily available ruthenium benzylidene complexes of the general type (RuCl2 (=CHPh)(L)(L')) (L, L' = P(cC5H9)3, PCy3 and/or a N-heterocyclic carbene) constitute a new class of catalyst ... [more ▼]

Air-stable and readily available ruthenium benzylidene complexes of the general type (RuCl2 (=CHPh)(L)(L')) (L, L' = P(cC5H9)3, PCy3 and/or a N-heterocyclic carbene) constitute a new class of catalyst precursors for atom transfer radical addition (ATRA, also called Kharasch addition) and atom transfer radical polymerisation (ATRP) of methyl methacrylate and styrene, and provide an unprecedented example for the involvement of ruthenium alkylidenes in radical reactions. They promote the addition of carbon tetrachloride to methyl methacrylate and styrene in moderate to high yield (Table 1). They also promote the polymerisation of methyl methacrylate and styrene in a controlled way with good to excellent yields (Table 2). The ligands L (P(cC5H9)3, PCy3 and/or a N-heterocyclic carbene) play a particularly important role in determining the rate of the polymerisation. A similarly pronounced influence is exerted by the substituents on the N-heterocyclic carbene. Our results indicate that: 􀀀 The catalysts decompose quickly under ATRA and ATRP conditions; 􀀀 Polymerisations are mediated by both (RuCl2(=CHPh)(L)(L')) complexes and ruthenium species bereft of the benzylidene moiety. [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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See detailControlled radical polymerization catalysed by ruthenium complexes: Variations on Ru-Cp#
Delfosse, Sébastien; Richel, Aurore ULg; Simal, Francois et al

in Matyjaszewski, K. (Ed.) Advances in Controlled/Living Radical Polymerization / ACS Symposium Series 854 (2003)

A series of isoelectronic ruthenium-based complexes of the general formula [RuX(Cp#)L2] (Cp# = cyclopentadienyl or cyclopentadienyl derivatives) were synthesized, and their relative catalytic activities ... [more ▼]

A series of isoelectronic ruthenium-based complexes of the general formula [RuX(Cp#)L2] (Cp# = cyclopentadienyl or cyclopentadienyl derivatives) were synthesized, and their relative catalytic activities were determined by monitoring the atom transfer radical polymerization of methyl methacrylate, n-butyl acrylate, and styrene. [RuCl(Cp*)(PPh3)2] and [RuCl(Ind)(PPh3)2] were found to be highly efficient catalysts for ATRP, producing polymers with narrow molecular weight distribution (Mw/Mn < 1.2). the following order of increasing efficiency was determined: [RuCl(Cp)(PPh3)2] << [RuCl(ind)(PPh3)2] < [RuCl(Cp*)(PPh3)2]. In sharp contrast, ruthena-carboranes were inefficient for ATRP, demonstrating therefore the prominent role of the Cp# ligand. The effect of the phosphine ligands was also investigated, and additional studies indicated that the release of a phosphine ligand occured prior to the activation of the carbon-halogen bond of both the initiator and polymer growing chain end by the unsaturated ruthenium center. [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 detailControlled Radical Polymerisation catalysed by rutehnium complexes. Variations on Ru-Cp#
Demonceau, Albert ULg; Delfosse, Sébastien; Guillaume, Bernard et al

in ACS Symposium Series (2002, August)

series of isoelectronic ruthenium-based complexes of the general formula [RuX(Cp#)L2] (Cp# = cyclopentadienyl or cyclopentadienyl derivatives) were synthesized, and their relative catalytic activities ... [more ▼]

series of isoelectronic ruthenium-based complexes of the general formula [RuX(Cp#)L2] (Cp# = cyclopentadienyl or cyclopentadienyl derivatives) were synthesized, and their relative catalytic activities were determined by monitoring the atom transfer radical polymerization of methyl methacrylate, n-butyl acrylate, and styrene. [RuCl(Cp*)(PPh3)2] and [RuCl(Ind)(PPh3)2] were found to be highly efficient catalysts for ATRP, producing polymers with narrow molecular weight distribution (Mw/Mn < 1.2). the following order of increasing efficiency was determined: [RuCl(Cp)(PPh3)2] << [RuCl(ind)(PPh3)2] < [RuCl(Cp*)(PPh3)2]. In sharp contrast, ruthena-carboranes were inefficient for ATRP, demonstrating therefore the prominent role of the Cp# ligand. The effect of the phosphine ligands was also investigated, and additional studies indicated that the release of a phosphine ligand occured prior to the activation of the carbon-halogen bond of both the initiator and polymer growing chain end by the unsaturated ruthenium center. [less ▲]

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See detailAtom transfer radical polymerisation (ATRP) and Kharasch addition mediated by titanium-ruthenium bimetallic systems
Richel, Aurore ULg; Delfosse, Sébastien; Demonceau, Albert ULg et al

Poster (2002, May)

Numerous studies have been directed towards the synthesis of early-Iate heterobimetallic complexes. Surprisingly, only few reports have been reported about their catalytic behaviour. However, their ... [more ▼]

Numerous studies have been directed towards the synthesis of early-Iate heterobimetallic complexes. Surprisingly, only few reports have been reported about their catalytic behaviour. However, their potential in homogeneous catalysis remains fantastic. Indeed, a cooperative work by the two metal centres in the complex would lead to new catalytic systems with unique reactivity. [less ▲]

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See detailControlled radical polymerisation catalysed by ruthenium complexes: Variations on Ru-Cp#
Delfosse, Sébastien; Guillaume, Bernard; Richel, Aurore ULg et al

in Polymer Preprints (2002)

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