Êtes-vous un étudiant de l'EPFL à la recherche d'un projet de semestre?

Travaillez avec nous sur des projets en science des données et en visualisation, et déployez votre projet sous forme d'application sur GraphSearch.

Découvrez-en plus sur les applications Graph.

Concept

Hydrogénation par transfert

L'hydrogénation par transfert est une technique d'hydrogénation dans laquelle la source en hydrogène n'est pas le dihydrogène, mais un autre « donneur en hydrogène ». Ces donneurs sont souvent des solvants comme l'hydrazine, le dihydronaphtalène, le dihydroanthracène, l'isopropanol, l'acide méthanoïque ou le cyclohexadiène. Cette technique est utilisée dans l'industrie et en synthèse organique du fait des inconvénients et des coûts liés à l'utilisation de H2. En synthèse organique, l'hydrogénation par transfert est utile pour la réduction de composés insaturés polaires comme les cétones, les aldéhydes ou les imines. Une application à grande échelle de l'hydrogénation par transfert est la liquéfaction du charbon en utilisant des « solvants donneurs » tels que la tétraline. Catalyseurs organométalliques En synthèse organique, une famille utile des catalyseurs transférant de l'hydrogène a été développée à base de complexes de ruthénium et de rhodium, souvent avec des ligand

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées

Chargement

Personnes associées

Chargement

Unités associées

Chargement

Concepts associés

Chargement

Cours associés

Chargement

Séances de cours associées

Chargement

Résumé

Source officielle

À propos de ce résultat

Publications associées (14)

Publications associées

Chargement

Personnes associées (1)

Personnes associées

Chargement

Unités associées (1)

Unités associées

Chargement

Concepts associés (16)

Concepts associés

Chargement

Cours associés (4)

Cours associés

Chargement

Séances de cours associées (10)

Séances de cours associées

Chargement

Highly dispersed cobalt oxides nanoparticles on activated carbon fibres as efficient structured catalysts for the transfer hydrogenation of m-nitrostyrene

Oliver Anthony Beswick, Paul Joseph Dyson, Lioubov Kiwi, Alexander Parastaev

The facile preparation of structured catalysts featuring highly-dispersed non-precious metal (Fe, Ni, Co) oxide nanoparticles stabilized within a super-microporous network of activated carbon fibres (ACF) is described. The catalyst morphology was controlled over multiple levels from the nano-designed active phase up to the macro-structure of the ACF support. A range of physicochemical techniques was used to characterize the catalyst and rationalize the catalytic data during chemoselective transfer hydrogenation of nitroarenes. The challenging reduction of m-nitrostyrene containing an easily reducible vinyl-group was obtained under mild conditions with a near-quantitative yield of m-vinylaniline using hydrazine hydrate as the reducing agent over CoOx/ACF as a structured catalyst. (C) 2016 Elsevier B.V. All rights reserved.

Elsevier Science Bv2017

Chargement

Iron Complexes for Hydrogen Activation and Catalytic Hydrogenation

Simona Mazza

Inspired by Nature several groups have developed structural and functional iron complexes mimicking the active site of the iron-hydrogenases, which show high reactivity in the H2 cleavage. Usually pendant bases have been incorporated onto families of Fe complexes in order to achieve active systems. In the view of these recent developments, in chapter two, we investigated the possibility of synthesizing novel iron (II) complexes bearing an amine internal base and providing an open site for substrate binding as catalysts for H2 activation. Pentacoordinated Fe(II) low spin complexes [(PhPNP)Fe(CO)(bdt)] (1), [(PhPNP)Fe-(CO)(Nbt)] (4), [(CyPNP)Fe(CO)(Nbt)] (5), [(dppe)Fe(CO)(Nbt)] (6) and the paramagnetic complex [(CyPNP)FeCl2] (10) have been synthesized and fully characterised. Unfortunately, when these complexes were tested as catalysts for hydrogenation reaction of a wide range of unsaturated substrates, no appreciable reactivity was observed. Same behaviour was observed in the case of complexes [(CyPNP)Fe(CO)(Cp)] (11) and [(CyPNP)Fe(CH3CN)(Cp)] (12) where the Cp ligand was installed in order to modulate the electronic and steric properties on the iron center. In chapter three, a new class of well-defined iron pincer complexes is reported. Several Fe(II) complexes supported by a 2,6-bis(phosphinito)pyridine ligand (PONOP) have been synthesized and fully characterised. In particular, the Fe-hydride complexes [(iPrPONOP)-Fe(CO)(H)Br] (14) and (iPrPONOP)Fe(CO)(H)(CH3CN) (15) could activate H2 at room temperature. Moreover, complexes 14 and 15 served as catalysts for the selective hydrogenation of aldehydes at room temperature. In presence of sodium formate as hydrogen donor, 14 and 15 showed an excellent reactivity in hydrogen transfer reaction of aldehydes. The mechanism of hydrogen activation and hydrogenation is discussed based on the observed reactivity of iron complexes. The feature of being chemoselective towards aldehydes and a broad functional-group tolerance make these iron-hydride systems remarkable in the class of the earth-abundant-metal hydrogenation catalysts. Chapter four is dedicated to the tuning of the Fe-PONOP systems reported in chapter three in order to synthesize similar iron(II) complexes exhibiting enhanced reactivity for H2 activation and hydrogenation of unsaturated substrates. As first attempt, complexes [(CyPONOP)Fe(CO)Br2] (22) and the analogous chloride [(CyPONOP)Fe(CO)Cl2] (23) bearing the stronger donor CyPONOP ligand were synthesized and tested as catalysts for hydrogenation reaction, but none of the substrates employed was reduced. As second attempt, the CO ligand was substituted with the better donor ligand tert-butyl isocyanide in presence of iPrPONOP as pincer ligand. Several Fe-PONOP complexes were synthesized and fully characterized. In particular the Fe-hydride complex [(iPrPONOP)Fe(tBuNC)(H)Br] (25) exhibited reactivity towards hydrogenation of aldehydes under the same reaction conditions reported for 14. No reaction was observed in presence of acetophenone, cyclohexene and 1-decene demonstrating that, although spectroscopically different, 25 did not exhibit enhanced reactivity relative to 14.

EPFL2015

Chargement

Base-Free Transfer Hydrogenation with an Ionic-Liquid-Supported Ruthenium eta(6)-Arene Bis(pyrazolyl)methane Catalyst

Paul Joseph Dyson, Andrew Douglas Phillips, Francisco Sepulveda

Ruthenium complexes of the type [RuCl(eta(6)-arene)-(NN)]X (X = BF4 or BPh4) featuring an eta(6)-arene ligand modified with an imidazolium ring and incorporating the bis(azo) chelating (NN) ligands 2-hydroxyphenylbis(3,5-dimethylpyrazol-1-yl) methane or 2-nitrophenylbis(3,5-dimethylpyrazol-1-yl) methane are reported. The catalytic activities of the complexes were evaluated in the transfer hydrogenation of benzaldehyde to benzyl alcohol with iPrOH as the hydrogen donor in the absence of a base and under biphasic conditions; one of the two phases was iPrOH, and the other was an ionic liquid. The catalysts featuring the imidazolium-modified eta(6)-arene could be recycled and reused with only a minor decrease in substrate conversion after multiple reaction cycles. The reaction rate was strongly influenced by the type of ionic liquid employed in the biphasic system.

Wiley-Blackwell2017

Chargement

Hydrogénation

L'hydrogénation est une réaction chimique qui consiste en l'addition d'une molécule de dihydrogène (H2) à un autre composé. Cette réaction est habituellement employée pour réduire ou saturer des com

Ruthénium

Le ruthénium est l'élément chimique de numéro atomique 44, de symbole Ru. Le ruthénium fait partie du groupe du platine, un sous-groupe de métaux de transition. Le corps simple ruthénium est un méta

Oxydoréduction en chimie organique

Les réactions d'oxydoréduction sont d'une importance capitale en chimie organique. Néanmoins, la structure des composés rend l'approche assez différente de ce que l'on observe en chimie inorganique ou

CH-223: Organometallic chemistry

Basic organometallic chemistry will be covered in this course.

Structure and bonding in organometallic compounds.
reactivity of organometallic compounds, stoichiometric reactions, catalyzed reactions and reaction mechanisms.

CH-422: Catalyst design for synthesis

This course on homogeneous catalysis provide a detailed understanding of how these catalysts work at a mechanistic level and give examples of catalyst design for important reactions (hydrogenation, olefin metathesis, cross-coupling).

CH-435: Catalytic asymmetric reactions in organic chemistry

This lecture presents the development of catalytic asymmetric reactions in organic chemistry, including important current topics of research in the field.