Center Communications Of Rmn

Sainte-Foy-lès-Lyon, France

Center Communications Of Rmn

Sainte-Foy-lès-Lyon, France

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Podgorsek A.,French National Center for Scientific Research | Salas G.,CNRS Institute of Chemistry | Campbell P.S.,CNRS Institute of Chemistry | Santini C.C.,CNRS Institute of Chemistry | And 6 more authors.
Journal of Physical Chemistry B | Year: 2011

The influence of the nature of two different ionic liquids, namely 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C 1C4Im][NTf2], and 1-butyl-2,3- dimethylimidazolium bis(trifluoromethylsulfonyl)imide, [C1C 1C4Im][NTf2], on the catalytic hydrogenation of 1,3-cyclohexadiene with [Rh(COD)(PPh3)2][NTf2] (COD=1,5-cyclooctadiene) was studied. Initially, the effect of different concentrations of 1,3-cyclohexadiene on the molecular interactions and on the structure in two ionic liquids was investigated by NMR and by molecular dynamic simulations. It was found that in both ionic liquids 1,3-cyclohexadiene is solvated preferentially in the lipophilic regions. Furthermore, the higher solubility of 1,3-cyclohexadiene in [C1C4Im][NTf 2] and the smaller positive values of the excess molar enthalpy of mixing for the 1,3-cyclohexadiene + [C1C4Im][NTf 2] system in comparison with 1,3-cyclohexadiene + [C 1C1C4Im][NTf2] indicate more favorable interactions between 1,3-cyclohexadiene and the C1C 4Im+ cation than with the C1C1C 4Im+ cation. Subsequently, diffusivity and conductivity measurements of the 1,3-cyclohexadiene + ionic liquid mixtures at different compositions allowed a characterization of mass and charge transport in the media and access to the ionicity of ionic liquids in the mixture. From the dependence of the ratio between molar conductivity and the conductivity inferred from NMR diffusion measurements, &imp/&NMR, on concentration of 1,3-cyclohexadiene in the ionic liquid mixture, it was found that increasing the amount of 1,3-cyclohexadiene leads to a decrease in the ionicity of the medium. Finally, the reactivity of the catalytic hydrogenation of 1,3-cyclohexadiene using [Rh(COD)(PPh3)2][NTf 2] performed in [C1C4Im][NTf2] at different compositions of 1,3-cyclohexadiene and in [C1C 1C4Im][NTf2] at one composition was related linearly to the viscosity, hence the reaction rate is determined by the mass transport properties of the media. © 2011 American Chemical Society.


Salas G.,CNRS Coordination Chemistry | Salas G.,National Polytechnic Institute of Toulouse | Salas G.,CNRS Institute of Chemistry | Santini C.C.,CNRS Institute of Chemistry | And 10 more authors.
Dalton Transactions | Year: 2011

Very stable suspensions of small sized (c.a. 1.2 nm) and homogeneously dispersed ruthenium nanoparticles (RuNPs) were obtained by decomposition, under H2, of (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 where n = 2; 4; 6; 8; 10) and in the presence of amines as ligands (1-octylamine, 1-hexadecylamine). These nanoparticles were compared to others stabilized either in pure ILs or by the same ligands in THF. NMR experiments (13C solution and DOSY) demonstrate that the amines are coordinated to the surface of the RuNPs. These RuNPs were investigated for the hydrogenation of aromatics and have shown a high level of recyclability (up to 10 cycles) with neither loss of activity nor significant agglomeration. © 2011 The Royal Society of Chemistry.


Campbell P.S.,CNRS Institute of Chemistry | Santini C.C.,CNRS Institute of Chemistry | Bouchu D.,Center Communications Of Spectrometrie Of Masse | Fenet B.,Center Communications Of Rmn | And 4 more authors.
Physical Chemistry Chemical Physics | Year: 2010

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 (η4-1, 5-cyclooctadiene)(η6-1,3,5-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. © 2010 the Owner Societies.


Campbell P.S.,CNRS Institute of Chemistry | Podgorsek A.,French National Center for Scientific Research | Gutel T.,CNRS Institute of Chemistry | Santini C.C.,CNRS Institute of Chemistry | And 7 more authors.
Journal of Physical Chemistry B | Year: 2010

The catalytic hydrogenation of 1,3-cyclohexadiene using [Rh(COD)(PPh 3)2]NTf2 (COD = 1,5-cyclooctadiene) was performed in two ionic liquids: 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C1C4Im][NTf 2], and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide, [C1C1C4Im][NTf2]. It is observed that the reaction is twice as fast in [C1C 4Im][NTf2] than in [C1C1C 4Im][NTf2]. To explain the difference in reactivity, molecular interactions and the microscopic structure of ionic liquid +1,3-cyclohexadiene mixtures were studied by NMR and titration calorimetry experiments, and by molecular simulation in the liquid phase. Diffusivity and viscosity measurements allowed the characterization of mass transport in the reaction media. We could conclude that the diffusivity of 1,3-cyclohexadiene is 1.9 times higher in [C1C4Im][NTf2] than in [C1C1C4Im][NTf2] and that this difference could explain the lower reactivity observed in [C1C 1C4Im][NTf2]. © 2010 American Chemical Society.

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