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

Poster (2003)

New ruthenium catalysts bearing N-heterocyclic carbene ligands for ATRP

in e-polymers (2003)

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

Ruthenium alkylidenes: a new class of catalysts for Kharasch addition and controlled radical polymerisation of vinyl monomers

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 ▲]

Controlled radical polymerization catalysed by ruthenium complexes: Variations on Ru-Cp#

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 ▲]

Probing the tacticity of ring-opened metathesis polymers of norbornene and norbornadiene diesters by NMR spectroscopy

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 ▲]

Radical polymerisation of methyl methacrylate catalysed by palladium(II) complexes containing chelating o-carboranyldiphosphine ligands

Poster (2002, August)

Atom transfer radical polymerisation (ATRP) and Kharasch addition mediated by titanium-ruthenium bimetallic systems

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 ▲]

Controlled radical polymerisation catalysed by ruthenium complexes: Variations on Ru-Cp#

in Polymer Preprints (2002)

Radical polymerisation of methyl methacrylate catalysed by palladium(II) complexes containing chelating o-carboranyldiphosphine ligands

in Polymer Preprints (2002), 43(2), 77-78

New in situ generated ruthenium catalysts bearing N-heterocyclic carbene ligands for the ring-opening metathesis polymerization of cyclooctene

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 ▲]