Controlled radical polymerization of vinyl monomers catalyzed by ruthenium N-heterocyclic carbene complexes

in Abstracts of Papers - American Chemical Society, National Meeting (2005), 230

As part of our program devoted to the development of new metal-NHC catalyst systems, we have launched a detailed investigation on the catalytic activity of ruthenium-p-cymene complexes bearing NHC ligands ... [more ▼]

As part of our program devoted to the development of new metal-NHC catalyst systems, we have launched a detailed investigation on the catalytic activity of ruthenium-p-cymene complexes bearing NHC ligands for the ring opening metathesis polymerization (ROMP) of cyclic olefins and for the ATRP of vinyl monomers. We report herein on the use for ATRP of [RuCl2(p-cymene)(NHC)] complexes generated in situ by combining the [RuCl2(p-cymene)]2 dimer with an imidazolium salt and a base such as potassium tert-butoxide, cesium carbonate or aluminum isopropoxide. [less ▲]

Catalytic applications of transition metal N-heterocyclic carbene complexes bearing nitrogen-containing side-groups

Poster (2004, July)

Herein, we report preliminary results in olefin cyclopropanation, olefin metathesis, atom transfer radical reactions (ATRA and ATRP), and in the Suzuki coupling reaction when catalyst systems were ... [more ▼]

Herein, we report preliminary results in olefin cyclopropanation, olefin metathesis, atom transfer radical reactions (ATRA and ATRP), and in the Suzuki coupling reaction when catalyst systems were generated in situ from [RuCl2(p-cymene)]2 or Pd(OAc)2, and an imidazolium salt bearing nitrogen-containing substituents. [less ▲]

Ruthenium-promoted radical processes toward fine chemistry

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 ▲]

Ruthenium N-heterocyclic carbene complexes: Versatile catalysts precursors for olefin metathesis, olefin cyclopropanation, and radical reactions

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 ▲]

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

Poster (2003, May)

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 ▲]

New ruthenium catalysts bearing N-heterocyclic carbene ligands for ATRP

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 ▲]

Ruthenium catalysts bearing N-heterocyclic carbene ligands in atom transfer radical reactions

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 ▲]

Atom Transfer Radical Polymerisation (ATRP) and Kharasch addition mediated by titanium-ruthenium bimetallic systems

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. 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 ▲]

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

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

Tuning of rethenium N-heterocyclic carbene catalysts for olefin polymerisation and fine chemistry

Scientific conference (2003)