CNRS, Laboratoire de Thermodynamique et Interactions Moléculaires, UMR 6272, 24 avenue des Landais, BP 80026, 63171 Aubière, France.
J Phys Chem B. 2011 Oct 27;115(42):12150-9. doi: 10.1021/jp206619c. Epub 2011 Sep 30.
The influence of the nature of two different ionic liquids, namely 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(4)Im][NTf(2)], and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(1)C(4)Im][NTf(2)], on the catalytic hydrogenation of 1,3-cyclohexadiene with [Rh(COD)(PPh(3))(2)][NTf(2)] (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 [C(1)C(4)Im][NTf(2)] and the smaller positive values of the excess molar enthalpy of mixing for the 1,3-cyclohexadiene + [C(1)C(4)Im][NTf(2)] system in comparison with 1,3-cyclohexadiene + [C(1)C(1)C(4)Im][NTf(2)] indicate more favorable interactions between 1,3-cyclohexadiene and the C(1)C(4)Im(+) cation than with the C(1)C(1)C(4)Im(+) 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, Λ(imp)/Λ(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)(PPh(3))(2)][NTf(2)] performed in [C(1)C(4)Im][NTf(2)] at different compositions of 1,3-cyclohexadiene and in [C(1)C(1)C(4)Im][NTf(2)] at one composition was related linearly to the viscosity, hence the reaction rate is determined by the mass transport properties of the media.
研究了两种不同的离子液体[C(1)C(4)Im][NTf(2)]（1-丁基-3-甲基咪唑双（三氟甲基磺酰）亚胺）和[C(1)C(1)C(4)Im][NTf(2)]（1-丁基-2,3-二甲基咪唑双（三氟甲基磺酰）亚胺）对[Rh(COD)(PPh(3))(2)][NTf(2)]（COD = 1,5-环辛二烯）催化氢化 1,3-环己二烯的影响。首先，通过 NMR 和分子动力学模拟研究了不同浓度的 1,3-环己二烯对两种离子液体中分子相互作用和结构的影响。结果发现，在两种离子液体中，1,3-环己二烯优先溶解在亲脂性区域。此外，与 1,3-环己二烯+[C(1)C(1)C(4)Im][NTf(2)]体系相比，1,3-环己二烯在[C(1)C(4)Im][NTf(2)]中的溶解度更高，并且 1,3-环己二烯+[C(1)C(4)Im][NTf(2)]体系的混合超额摩尔焓为正值较小，这表明 1,3-环己二烯与 C(1)C(4)Im(+)阳离子之间的相互作用比与 C(1)C(1)C(4)Im(+)阳离子之间的相互作用更有利。随后，对不同组成的 1,3-环己二烯+离子液体混合物的扩散率和电导率测量允许对介质中的质量和电荷传输进行表征，并获得混合物中离子液体的离子性。从摩尔电导率与 NMR 扩散测量推断的电导率之比Λ(imp)/Λ(NMR)与离子液体混合物中 1,3-环己二烯浓度的关系发现，随着 1,3-环己二烯用量的增加，介质的离子性降低。最后，在不同组成的[C(1)C(4)Im][NTf(2)]和[C(1)C(1)C(4)Im][NTf(2)]中的一个组成中使用[Rh(COD)(PPh(3))(2)][NTf(2)]进行 1,3-环己二烯的催化氢化反应的活性与粘度线性相关，因此反应速率由介质的质量传输性质决定。
