Karine Philippot

An Efficient Strategy to Drive Nanoparticles into Carbon Nanotubes and the Remarkable Effect of Confinement on Their Catalytic Performance

Are you in? Bimetallic PtRu nanoparticles have been selectively confined inside or deposited outside carbon nanotubes (see picture). The confined nanoparticles display significantly higher selectivity and catalytic activity in hydrogenation reactions.

Ruthenium Nanoparticles Stabilized by N-Heterocyclic Carbenes: Ligand Location and Influence on Reactivity

We thank V. Colliere and L. Datas (UPS-TEMSCAN) and P. Lecante (CNRS-CEMES) for TEM/HR-TEM and WAXS facilities, respectively. CNRS and ANR (Siderus project ANR-08-BLAN-0010-03) are also thanked for financial support. P.L. is grateful to the Spanish Ministerio de Educacion for a research contract. Financial support from the Junta de Andalucia (project no. FQM-3151) and the Spanish Ministerio de Ciencia e Innovacion (projects CTQ2010-17476 and CONSOLIDER-INGENIO 2010 CSD2007-00006, FEDER support) is acknowledged. O.R.-W. thanks the Spanish Ministerio de Ciencia e Innovacion for a research grant.

Influence of the self-organization of ionic liquids on the size of ruthenium nanoparticles: effect of the temperature and stirring

The size of ruthenium nanoparticles is governed by the degree of self-organization of the imidazolium based ionic liquid in which they are generated from (η4-1,5-cyclooctadiene)(η6-1,3,5-cyclooctatriene)ruthenium: the more structured the ionic liquid, the smaller the size.

Organized 3D-alkyl imidazolium ionic liquids could be used to control the size of in situ generated ruthenium nanoparticles?

The synthesis of ruthenium nanoparticles, RuNPs from the organometallic complex (η4-1,5-cyclooctadiene)(η6-1,3,5-cyclooctatriene)ruthenium(0), Ru(COD)(COT) in various imidazolium derived ionic liquids, ILs: [RMIm][NTf2] (R = CnH2n + 1 with n = 2; 4; 6; 8; 10), and [R2Im][NTf2] (RBu) and [BMMIm][NTf2] has been performed, under 0.4 MPa of H2, at 25 °C or at 0 °C with or without stirring. A relationship between the size of IL non-polar domains calculated by molecular dynamics simulation and the RuNP size measured by TEM has been found, suggesting that the phenomenon of crystal growth is probably controlled by the local concentration of Ru(COD)(COT) and consequently is limited to the size of the non-polar domains. Moreover, the rigid 3D organization based on C2–H⋯anion bonding and chosen experimental conditions, could explain the non-aggregation of RuNPs.

Catalytic investigation of rhodium nanoparticles in hydrogenation of benzene and phenylacetylene

Nanoparticles of rhodium embedded in polyvinylpyrrolidone (PVP), as catalyst, were investigated in the hydrogenation of different substrates (benzene, phenylacetylene, norbornene, quinoline, adiponitrile). The solid was used as a heterogeneous catalyst or as a soluble heterogeneous catalyst in biphasic conditions (liquid/liquid) when the catalyst was dissolved in water. In both cases, the kinetics of the catalytic reaction were found to be zero-order in respect to the substrate and first-order with respect to hydrogen and catalyst. The higher hydrogenation reaction rate was found for benzene by using biphasic conditions. The [Rh-PVP] catalyst has shown an efficient activity for the catalytic hydrogenation of norbornene, quinoline and adiponitrile into norbornane, tetrahydroquinoline and 6-aminocapronitrile.

Synthesis, characterization and catalytic reactivity of ruthenium nanoparticles stabilized by chiral N-donor ligands

The decomposition of the organometallic precursor [Ru(cod)(cot)] (cod = 1,5-cyclooctadiene; cot = 1,3,5-cyclooctatriene) under mild conditions (room temperature, 3 bars H2) and in the presence of optically pure ligands, L*, namely (R)-2-aminobutanol 1, amino(oxazolines) (2, 3), hydroxy(oxazoline) (4) and bis(oxazolines) (5–8), leads to stable ruthenium nanoparticles exhibiting a mean diameter between 1.6–2.5 nm. These nanoparticles can be isolated and re-dispersed. They display different mean sizes, shapes and dispersions depending on the stabilizer nature. These new colloids (Ru1–Ru18) have been characterized by both solid state and molecular chemistry techniques, including TEM/HRTEM, WAXS, elemental analysis, and IR and NMR spectroscopy. To further characterize the surface state of these particles, their catalytic behaviour has been examined in the reduction of organic prochiral unsaturated substrates. Although the asymmetric induction obtained is modest, it reveals the influence of the asymmetric ligand coordinated at the surface of the particles.

Novel, Spongelike Ruthenium Particles of Controllable Size Stabilized Only by Organic Solvents

Soluble ruthenium nanoparticles of uniform size (see picture) with a porous spongelike structure were obtained by the reaction of [Ru(C(8)H(10))(C(8)H(12))] with H(2) in methanol or THF/methanol. The particle size can be controlled in the range 15-100 nm by varying the MeOH/THF ratio. The particles catalyze benzene hydrogenation without modification of their size or structure. Their formation is proposed to occur in the droplets of a nanosized emulsion, which act as nanoreactors.

Organometallic Ruthenium Nanoparticles: A Comparative Study of the Influence of the Stabilizer on their Characteristics and Reactivity

The use of metal nanoparticles as catalysts is a topic of growing interest at the frontier between homogeneous and heterogeneous catalysis. Metal nanoparticles are highly interesting systems owing to their high number of surface atoms, which give rise to numerous active sites. Furthermore, the surface properties of metal nanoparticles can be tuned by the addition of a stabilizer, for example, a polymer, a surfactant, or a ligand, or by combining a metal with a support to take profit of their synergy to orientate a catalytic reaction. Significant efforts are being made towards the synthesis of metal nanoparticles in general and, more precisely, towards the preparation of ligand‐stabilized nanoparticles in which the size, shape, and surface state are controlled. Since ligands can modulate both the electronic and steric environment at the surface of the particles, numerous studies are presently devoted to analyze the influence of ligands on the stabilization of nanoparticles and on their surface properties. Such studies are of key importance to develop more active and selective nanocatalysts. In that context, ruthenium nanoparticles are candidates of choice as they can be characterized inter alia by nuclear magnetic resonance, as ruthenium displays little or no Knight shift and since they are active catalysts for hydrogenation reactions of, for example, arenes, olefins, and alkynes. In this Review, we present an overview of our group’s efforts in the synthesis of ligand‐stabilized ruthenium nanoparticles of controlled size and surface state using different types of ligands. We report the influence of nitrogen‐, sulfur‐, silicon‐, phosphorus‐ and carbon‐ containing ligands as coordinating atoms to the metal surface, on their stabilization, as well as on their surface reactivity, in comparison with sterically‐stabilized Ru nanoparticles prepared following the same organometallic approach, but using polymers or “nanoreactors” made of alcohols or ionic liquids that allow for control of the growth of the particles by a confinement effect. Nanoparticles of other metals are also described when appropriate.

A simple and reproducible method for the synthesis of silica-supported rhodium nanoparticles and their investigation in the hydrogenation of aromatic compounds

Colloidal suspensions of rhodium nanoparticles have been easily prepared in aqueous solution by chemical reduction of the precursor RhCl3·3H2O in the presence of the surfactant N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium chloride (HEA16Cl) and further used to immobilize rhodium nanoparticles on silica by simple impregnation. The obtained silica-supported rhodium nanoparticles have been investigated by adapted characterization methods such as transmission electron microscopy and X-ray photoelectron spectroscopy. A particle size increase from 2.4 to 5 nm after the silica immobilization step and total elimination of the surfactant has been observed. This “heterogeneous” catalyst displayed good activities for the hydrogenation of mono-, di- alkylsubstituted and/or functionalized aromatic derivatives in water under atmospheric hydrogen pressure and at room temperature. In all cases, the catalyst could be recovered several times after a simple decantation or filtration and reused without any significant loss in catalytic activity. This supported catalyst has also been tested under higher hydrogen pressure giving rise to TOFs reaching 6430 h−1 at 30 bar and in terms of catalytic lifetime 30 000 TTO in 8.5 h for pure anisole hydrogenation at 40 bar.

A novel stabilisation model for ruthenium nanoparticles in imidazolium ionic liquids: in situ spectroscopic and labelling evidence

In situ labelling and spectroscopic experiments are used to explain the key points in the stabilisation of ruthenium nanoparticles (RuNPs) generated in imidazolium-based ionic liquids (ILs) by decomposition of (eta(4)-1,5-cyclooctadiene)(eta(6)-1,3,5-cyclooctatriene)ruthenium(0), Ru(COD)(COT), under dihydrogen. These are found to be: (1) the presence of hydrides at the RuNP surface and, (2) the confinement of RuNPs in the non-polar domains of the structured IL, induced by the rigid 3-D organisation. These results lead to a novel stabilisation model for NPs in ionic liquids.