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Indenylidene Complexes (indenylidene + complex)

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Chemistry100%

Selected Abstracts

Mixed Isobutylphobane/N-Heterocyclic Carbene Ruthenium- Indenylidene Complexes: Synthesis and Catalytic Evaluation in Olefin Metathesis Reactions

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010
Xavier Sauvage
Abstract Two new second generation ruthenium(II) dichloride-indenylidene complexes [RuCl2(9-isobutylphosphabicyclo[3.3.1]nonane)(NHC)(3-phenyl-1-indenylidene)], where NHC=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) or its unsaturated imidazol-2-ylidene analogue (IMes), were isolated in high yields upon heating a tetrahydrofuran (THF) solution of the diphosphane complex [RuCl2(isobutylphobane)2(3-phenyl-1-indenylidene)] with a two-fold excess of the corresponding imidazol(in)ium-2-carboxylate zwitterions. Both products were characterized by 1H, 13C, and 31P,NMR spectroscopy, and the molecular structure of [RuCl2(isobutylphobane)(SIMes)(3-phenyl-1-indenylidene)] was determined by X-ray diffraction analysis. A close inspection of the packing structure revealed the presence of different types of intra- and intermolecular interactions that enhanced the global stability of the crystals, while low temperature NMR experiments showed the existence of two distinct rotational isomers due to the unsymmetrical nature of the phobane ligand. The catalytic activity of both compounds was assessed in olefin metathesis using benchmark ring-opening metathesis polymerization, ring-closing metathesis (RCM), and cross-metathesis reactions, and compared with those of related first and second generation ruthenium-benzylidene and indenylidene catalyst precursors. Kinetic studies confirmed the high thermal stability of the mixed isobutylphobane/N-heterocyclic carbene complexes, which suffered from a slow initiation efficiency compared to other catalytic systems based on the tricyclohexylphosphane ligand. However, the remarkable robustness of [RuCl2(isobutylphobane)(SIMes)(3-phenyl-1-indenylidene)] was beneficial for performing the RCM of diethyl 2,2-bis(2-methylallyl)malonate. Monitoring the formation of the ruthenium-methylidene active species [RuCl2(isobutylphobane)(SIMes)(CH2)] derived from this precursor further demonstrated its ability to sustain long reaction times and high temperatures required to carry out the RCM of tetrasubstituted olefins. [source]

Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009
Xavier Sauvage
Abstract Four homobimetallic ruthenium-(p -cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade pathway from the ethylene complex [(p -cymene)Ru(,-Cl)3RuCl(PCy3)(,2 -C2H4)] (7a). All the products were isolated and fully characterized by IR and NMR spectroscopies. The molecular structure of the indenylidene complex 11 was determined by X-ray crystallographic analysis. The catalytic activity of the four complexes was probed in various types of olefin metathesis reactions and compared with those of a related homobimetallic ruthenium-benzylidene complex, as well as first, second, and third generation monometallic Grubbs catalysts. In the ring-closing metathesis (RCM) of diethyl diallylmalonate, the homobimetallic ruthenium-indenylidene complex 11 outperformed all the ruthenium-benzylidene complexes under investigation and was only slightly less efficient than its monometallic parent. Cross-metathesis experiments with ethylene showed that deactivation of ruthenium-benzylidene or indenylidene complexes was due to the rapid bimolecular decomposition of methylidene active species into ethylene complex 7a. Vinylidene and allenylidene complexes were far less efficient catalyst precursors for ring-opening metathesis polymerization (ROMP) or RCM and remained inert under an ethylene atmosphere. Their catalytic activity was, however, substantially enhanced upon addition of an acidic co-catalyst that most likely promoted their in situ transformation into indenylidene species. Due to its straightforward synthesis and high metathetical activity, homobimetallic ruthenium-indenylidene complex 11 is a valuable intermediate for the preparation of the Hoveyda,Grubbs catalyst [Cl2Ru(PCy3)(CH- o -O- i- PrC6H4)] via stoichiometric cross-metathesis with 2-isopropoxystyrene. The procedure did not require any sacrificial phosphine and the transition metal not incorporated into the final product was easily recovered and recycled at the end of the process. [source]

ChemInform Abstract: Indenylidene Complexes of Ruthenium: Optimized Synthesis, Structure Elucidation, and Performance as Catalysts for Olefin Metathesis , Application to the Synthesis of the ADE-Ring System of Nakadomarin A.

CHEMINFORM, Issue 17 2002
Alois Fuerstner
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

The Influence of Phosphane Ligands on the Versatility of Ruthenium,Indenylidene Complexes in Metathesis

CHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2010
Julie Broggi Dr.
Abstract The aim of the present study is to develop readily available and stable pre-catalysts that could be easily prepared on large scale from simple starting materials. Based on the hypothesis that substitution of classical PCy3 with phosphanes of varying electron-donating properties could be a straightforward manner to improve catalytic activity, a methodical study dealing with the effect of phosphane fine-tuning in ruthenium,indenylidene catalysts was performed. Challenged to establish how the electronic properties of para -substituted phosphane ligands translate into catalyst activity, the versatile behaviour of these new ruthenium,indenylidene complexes was investigated for a number of metathesis reactions. [source]

Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009
Xavier Sauvage
Abstract Four homobimetallic ruthenium-(p -cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade pathway from the ethylene complex [(p -cymene)Ru(,-Cl)3RuCl(PCy3)(,2 -C2H4)] (7a). All the products were isolated and fully characterized by IR and NMR spectroscopies. The molecular structure of the indenylidene complex 11 was determined by X-ray crystallographic analysis. The catalytic activity of the four complexes was probed in various types of olefin metathesis reactions and compared with those of a related homobimetallic ruthenium-benzylidene complex, as well as first, second, and third generation monometallic Grubbs catalysts. In the ring-closing metathesis (RCM) of diethyl diallylmalonate, the homobimetallic ruthenium-indenylidene complex 11 outperformed all the ruthenium-benzylidene complexes under investigation and was only slightly less efficient than its monometallic parent. Cross-metathesis experiments with ethylene showed that deactivation of ruthenium-benzylidene or indenylidene complexes was due to the rapid bimolecular decomposition of methylidene active species into ethylene complex 7a. Vinylidene and allenylidene complexes were far less efficient catalyst precursors for ring-opening metathesis polymerization (ROMP) or RCM and remained inert under an ethylene atmosphere. Their catalytic activity was, however, substantially enhanced upon addition of an acidic co-catalyst that most likely promoted their in situ transformation into indenylidene species. Due to its straightforward synthesis and high metathetical activity, homobimetallic ruthenium-indenylidene complex 11 is a valuable intermediate for the preparation of the Hoveyda,Grubbs catalyst [Cl2Ru(PCy3)(CH- o -O- i- PrC6H4)] via stoichiometric cross-metathesis with 2-isopropoxystyrene. The procedure did not require any sacrificial phosphine and the transition metal not incorporated into the final product was easily recovered and recycled at the end of the process. [source]

Imidazol(in)ium-2-carboxylates as N-Heterocyclic Carbene Precursors for the Synthesis of Second Generation Ruthenium Metathesis Catalysts

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009
Xavier Sauvage
Abstract Five well-known ruthenium-N-heterocyclic carbene (NHC) catalysts for olefin metathesis and related reactions, including the second generation Grubbs and Hoveyda,Grubbs catalysts, were prepared by phosphane exchange between first generation ruthenium-benzylidene or indenylidene complexes and NHCs generated in situ upon thermolysis of imidazol(in)ium-2-carboxylates. Because N-heterocyclic carbene carbon dioxide adducts (NHC,CO2) are stable zwitterionic compounds that can be stored and handled with no particular precautions, this procedure is particularly attractive from a practical point of view. Reaction courses were conveniently monitored by 31P,NMR spectroscopy and the experimental conditions were carefully adjusted to obtain high yields of pure products within short periods of time. [source]

Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009
Xavier Sauvage
Abstract Four homobimetallic ruthenium-(p -cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade pathway from the ethylene complex [(p -cymene)Ru(,-Cl)3RuCl(PCy3)(,2 -C2H4)] (7a). All the products were isolated and fully characterized by IR and NMR spectroscopies. The molecular structure of the indenylidene complex 11 was determined by X-ray crystallographic analysis. The catalytic activity of the four complexes was probed in various types of olefin metathesis reactions and compared with those of a related homobimetallic ruthenium-benzylidene complex, as well as first, second, and third generation monometallic Grubbs catalysts. In the ring-closing metathesis (RCM) of diethyl diallylmalonate, the homobimetallic ruthenium-indenylidene complex 11 outperformed all the ruthenium-benzylidene complexes under investigation and was only slightly less efficient than its monometallic parent. Cross-metathesis experiments with ethylene showed that deactivation of ruthenium-benzylidene or indenylidene complexes was due to the rapid bimolecular decomposition of methylidene active species into ethylene complex 7a. Vinylidene and allenylidene complexes were far less efficient catalyst precursors for ring-opening metathesis polymerization (ROMP) or RCM and remained inert under an ethylene atmosphere. Their catalytic activity was, however, substantially enhanced upon addition of an acidic co-catalyst that most likely promoted their in situ transformation into indenylidene species. Due to its straightforward synthesis and high metathetical activity, homobimetallic ruthenium-indenylidene complex 11 is a valuable intermediate for the preparation of the Hoveyda,Grubbs catalyst [Cl2Ru(PCy3)(CH- o -O- i- PrC6H4)] via stoichiometric cross-metathesis with 2-isopropoxystyrene. The procedure did not require any sacrificial phosphine and the transition metal not incorporated into the final product was easily recovered and recycled at the end of the process. [source]

The Influence of Phosphane Ligands on the Versatility of Ruthenium,Indenylidene Complexes in Metathesis

CHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2010
Julie Broggi Dr.
Abstract The aim of the present study is to develop readily available and stable pre-catalysts that could be easily prepared on large scale from simple starting materials. Based on the hypothesis that substitution of classical PCy3 with phosphanes of varying electron-donating properties could be a straightforward manner to improve catalytic activity, a methodical study dealing with the effect of phosphane fine-tuning in ruthenium,indenylidene catalysts was performed. Challenged to establish how the electronic properties of para -substituted phosphane ligands translate into catalyst activity, the versatile behaviour of these new ruthenium,indenylidene complexes was investigated for a number of metathesis reactions. [source]