Phosphine oxide functionalised imidazolium ionic liquids as tuneable ligands for lanthanide complexation

A series of novel, phosphine oxide functionalised ionic liquids have been synthesised and their application as tuneable lanthanide complexing agents is demonstrated.

Chlorostannate(II) Ionic Liquids: Speciation, Lewis Acidity, and Oxidative Stability

The anionic speciation of chlorostannate(II) ionic liquids, prepared by mixing 1-alkyl-3-methylimidazolium chloride and tin(II) chloride in various molar ratios, chi(SnCl2), was investigated in both solid and liquid states. The room temperature ionic liquids were investigated by Sn-119 NMR spectroscopy, X-ray photoelectron spectroscopy, and viscometry. Crystalline samples were studied using Raman spectroscopy, single-crystal X-ray crystallography, and differential scanning calorimetry. Both liquid and solid systems (crystallized from the melt) contained [SnCl3](-) in equilibrium with Cl- when chi(SnCl2) < 0.50, [SnCl3](-) in equilibrium with [Sn2Cl5](-) when chi(SnCl2) > 0.50, and only [SnCl3](-) when chi(SnCl2) = 0.50. Tin(II) chloride was found to precipitate when chi(SnCl2) > 0.63. No evidence was detected for the existence of [SnCl4](-) across the entire range of chi(SnCl2) although such anions have been reported in the literature for chlorostannate(II) organic salts crystallized from organic solvents. Furthermore, the Lewis acidity of the chlorostannate(II)-based systems, expressed by their Gutmann acceptor number, has been determined as a function of the composition, chi(SnCl2), to reveal Lewis acidity for chi(SnCl2) > 0.50 samples comparable to the analogous systems based on zinc(II). A change of the Lewis basicity of the anion was estimated using H-1 NMR spectroscopy, by comparison of the measured chemical shifts of the C-2 hydrogen in the imidazolium ring. Finally, compositions containing free chloride anions (chi(SnCl2) < 0.50) were found to oxidize slowly in air to form a chlorostannate(IV) ionic liquid containing the [SnCl6](2-) anion.

Density and viscosity of several pure and water-saturated ionic liquids

Densities and viscosities were measured as a function of temperature for six ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium ethylsulfate and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide. The density and the viscosity were obtained using a vibrating tube densimeter from Anton Paar and a rheometer from Rheometrics Scientific at temperatures up to 393 K and 388 K with an accuracy of 10-3 g cm-3 and 1%, respectively. The effect of the presence of water on the measured values was also examined by studying both dried and water-saturated samples. A qualitative analysis of the evolution of density and viscosity with cation and anion chemical structures was performed. © The Royal Society of Chemistry 2006.

Solubility of carbon dioxide and ethane in three ionic liquids based on the bis{(trifluoromethyl)sulfonyl}imide anion

The objective of this work was to study the influence of changing the cation of the ionic liquid (IL) on gas solubility. For this purpose, the low-pressure solubility of carbon dioxide and of ethane in three ILs based on the bis{(trifluoromethyl)sulfonyl}imide anion ([NTf2](-)) was determined experimentally. Solubility data is reported for 1-ethyl-3-methylimidazolium ([C(1)C(2)Im](+)), 1-butyl-1-methylpyrrolidinium ([C(1)C(4)pyrr](+)) and propylcholinium ([N1132-OH](+)) bis{(trifluoromethyl)sulfonyl}imide ILs between 300 and 345 K. These data are precise to within +/- 1% and accurate to within +/- 5%. In these ILs, carbon dioxide (mole fraction solubility between 1 and 3 x 10(-2), molarity between 0.03 and 0.1 mol L-1) is one order of magnitude more soluble than ethane. The effect of changing the cation is small but significant. Changing the cation has a similar effect on both gases even if the differences are more pronounced in the case of ethane with the order of solubility [C(1)C(4)pyrr][NTf2] > [C(1)C(2)Im][NTf2] > [N1132-OH][NTf2]. For all the systems, the solubility decreases with temperature corresponding to exothermic processes of solvation and negative enthalpies and entropies of solvation were calculated. The properties of solvation of the two gases in [C(1)C(4)pyrr][NTf2] do not vary significantly with temperature while important variations are depicted for both gases in [C(1)C(2)Im][NTf2]. (c) 2007 Elsevier B.V. All rights reserved.

High-pressure volumetric properties of imidazolium-based ionic liquids: Effect of the anion

The densities of five imidazolium-based ionic liquids (ILs) (1-butyl-3-methylimidazolium tetrafluoroborate, [CiC4-Im][BF 4]; 1-butyl-3-methylimidazolium hexafluorophosphate, [CiC 4Im][PF6]; 1-butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [C1C4Im][Tf 2N]; 1-ethyl-3-methylimidazoliumbis{(trifluoromethyl)sulfonyl}-imide, [C1C2Im][Tf2N]; l-ethyl-3-methylimidazolium ethylsulfate, [C1C2Im][EtSO4]) were measured as a function of temperature from (293 to 415) K and over an extended pressure range from (0.1 to 40) MPa using a vibratingtube densimeter. Knowledge of the variation of the density with temperature and pressure allows access to the mechanical coefficients: thermal expansion coefficient and isothermal compressibility. The effects of the anion and of the length of the alkyl chain on the imidazolium ring on the volumetric properties were particularly examined. The mechanical coefficients were compared with those of common organic solvents, water and liquid NaCl. Finally, a prediction model, based on an "ideal" volumetric behavior of the ILs, is proposed to allow calculation of the molar volume of imidazolium-based ionic liquids as a function of temperature. ©2007 American Chemical Society.

Thermophysical properties of ammonium-based bis{(trifluoromethyl)sulfonyl} imide ionic liquids: Volumetric and transport properties

Density, rheological properties, and conductivity of a homologous series of ammonium-based ionic liquids N-alkyl-triethylammonium bis{(trifluoromethyl) sulfonyl}imide were studied at atmospheric pressure as a function of alkyl chain length on the cation, as well as of the temperature from (293.15 to 363.15) K. From these investigations, the effect of the cation structure was quantified on each studied properties, which demonstrated, as expected, a decrease of the density and conductivity, a contrario of an increase of the viscosity with the alkyl chain length on the ammonium cation. Furthermore, rheological properties were measured for both pure and water-saturated ionic liquids. The studied ionic liquids were found to be Newtonian and non-Arrhenius. Additionally, the effect of water content in the studied ionic liquids on their viscosity was investigated by adding water until they were saturated at 293.15 K. By comparing the viscosity of pure ionic liquids with the data measured in water-saturated samples, it appears that the presence of water decreases dramatically the viscosity of ionic liquids by up to three times. An analysis of involved transport properties leads us to a classification of the studied ionic liquids in terms of their ionicity using the Walden plot, from which it is evident that they can be classified as "good" ionic liquids. Finally, from measured density data, different volumetric properties, that is, molar volumes and thermal expansion coefficients were determined as a function of temperature and of cationic structure. Based on these volumetric properties, an extension of Jacquemin's group contribution model has been then established and tested for alkylammonium-based ionic liquids within a relatively good uncertainty close to 0.1 %. © 2012 American Chemical Society.

Thermophysical properties, low pressure solubilities and thermodynamics of solvation of carbon dioxide and hydrogen in two ionic liquids based on the alkylsulfate anion

Densities and viscosities of the ionic liquid 1-butyl-3-methylimidazolium octylsulfate, [C4C1Im][C8SO4] were measured as a function of temperature between 313 K and 395 K. Solubilities of hydrogen and carbon dioxide were determined, between 283 K and 343 K, and at pressures close to atmospheric in [C4C1Im][C 8SO4] and in another ionic liquid based on the alkylsulfate anion-1-ethyl-3-methylimidazolium ethylsulfate, [C 2C1Im][C2SO4]. Density and viscosity were measured using a vibrating tube densimeter from Anton Paar and a rheometer from Rheometrics Scientific with accuracies of 10-3 g cm -3 and 1%, respectively. Solubilities were obtained using an isochoric saturation technique and, from the variation of solubility with temperature, the partial molar thermodynamic functions of solvation, such as the standard Gibbs energy, the enthalpy, and the entropy, are calculated. The precision of the experimental data, considered as the average absolute deviation of the Henry's law constants from appropriate smoothing equations, is better than ±1%. © The Royal Society of Chemistry.

Methylation using dimethylcarbonate catalysed by ionic liquids under continuous flow conditions

The ionic liquid, tributylmethylammonium methylcarbonate, has been employed as a catalytic base for clean N-methylation of indole with dimethylcarbonate. The reaction conditions were optimised under microwave heating to give 100% conversion and 100% selectivity to N-methylindole, and subsequently transferred to a high temperature/high pressure (285 degrees C/150 bar) continuous flow process using a short (3 min) residence time and 2 mol% of the catalyst to efficiently methylate a variety of different amines, phenols, thiophenols and carboxylic acid substrates. The extremely short residence times, versatility, and high selectivity have significant implications for the synthesis of a wide range of pharmaceutical intermediates, as high product throughputs can be obtained via this scalable continuous flow protocol. It has also been shown that the ionic liquid can be generated in situ from tributylamine, which has the net effect of transforming an ineffective stoichiometric base into a highly efficient catalyst for this broad class of reactions.

Determining relative rates of cellulose dissolution in ionic liquids through in situ viscosity measurement

Using in situ viscosity measurement, the rate of cellulose dissolution in a number of ionic liquids has been determined allowing their performance as solvents to be quantitatively assessed. 1-Butyl-3-methylimidazolium ethanoate was shown to dissolve cellulose faster than analogous ionic liquids with chloride or dimethylphosphate anions. Analysis of the data highlights the influence of both anion basicity and relative concentration on the rate of dissolution.

On the Mechanism of Lewis Acid Catalyzed Glucose Transformations in Ionic Liquids

A complementary computational and experimental study of the reactivity of Lewis acidic CrCl2, CuCl2 and FeCl2 catalysts towards glucose activation in dialkylimidazolium chloride ionic liquids is performed. The selective dehydration of glucose to 5-hydroxymethylfurfural (HMF) proceeds through the intermediate formation of fructose. Although chromium(II) and copper(II) chlorides are able to dehydrate fructose with high HMF selectivity, reasonable HMF yields from glucose are only obtained with CrCl2 as the catalyst. Glucose conversion by CuCl2 is not selective, while FeCl2 catalyst does not activate sugar molecules. These differences in reactivity are rationalized on the basis of in situ X-ray absorption spectroscopy measurements and the results of density functional theory calculations. The reactivity in glucose dehydration and HMF selectivity are determined by the behavior of the ionic liquid-mediated Lewis acid catalysts towards the initial activation of the sugar molecules. The formation of a coordination complex between the Lewis acidic Cr2+ center and glucose directs glucose transformation into fructose. For Cu2+ the direct coordination of sugar to the copper(II) chloride complex is unfavorable. Glucose deprotonation by a mobile Cl- ligand in the CuCl42- complex initiates the nonselective conversion. In the course of the reaction the Cu2+ ions are reduced to Cu+. Both paths are prohibited for the FeCl2 catalyst.

Microwave Irradiation for the Facile Synthesis of Transition-Metal Nanoparticles (NPs) in Ionic Liquids (ILs) from Metal-Carbonyl Precursors and Ru-, Rh-, and Ir-NP/IL Dispersions as Biphasic Liquid-Liquid Hydrogenation Nanocatalysts for Cyclohexene

Stable chromium, molybdenum, tungsten, manganese, rhenium, ruthenium, osmium, cobalt, rhodium, and iridium metal nanoparticles (MNPs) have been reproducibly obtained by facile, rapid (3 min), and energysaving 10 W microwave irradiation (MWI) under an argon atmosphere from their metal–carbonyl precursors [Mx(CO)y] in the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]). This MWI synthesis is compared to UV-photolytic (1000 W, 15 min) or conventional thermal decomposition (180–2508C, 6–12 h) of [Mx(CO)y] in ILs. The MWIobtained nanoparticles have a very small (<5 nm) and uniform size and are prepared without any additional stabilizers or capping molecules as long-term stable M-NP/IL dispersions (characterization by transmission electron microscopy (TEM), transmission electron diffraction (TED), and dynamic light scattering (DLS)). The ruthenium, rhodium, or iridium nanoparticle/IL dispersions are highly active
and easily recyclable catalysts for the biphasic liquid–liquid hydrogenation of cyclohexene to cyclohexane with activities of up to 522 (mol product)(mol Ru)1h1 and 884 (mol product)(molRh)1h1 and give almost quantitative conversion within 2 h at 10 bar H2 and 908C. Catalyst poisoning experiments with CS2 (0.05 equiv per Ru) suggest a heterogeneous surface catalysis of RuNPs.

Tuning solute redox potentials by varying the anion component of room temperature ionic liquids

The electrode potentials for the two one electron oxidations of 1,2-diferrocenylethylene (bisferrocene, BF) were studied relative to that of the one electrode oxidation of decamethylferrocene in a variety of RTILs. The difference in these potentials was found to be very sensitive to the anion component of the ionic liquid showing the scope of these solutes as 'designer media' to tune the thermodynamic properties of solutes dissolved in them.

Dioxouranium(VI) extraction in microchannels using ionic liquids

The extraction of uranium(VI) from aqueous nitric acid solutions by tributylphosphate {TBP; 30%(v/v)} dissolved in the ionic liquid 1-butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide was investigated. The experiments were performed in a Teflon microchannel of 0.5 mm internal diameter, while the dioxouranium(VI) concentrations in the aqueous and the ionic liquid phases were determined by UV-Vis spectroscopy. The effects of initial nitric acid concentration (0.01-3 M), residence time, and phase flow rate ratio were studied. It was found that, with increasing nitric acid concentration, the percentage of dioxouranium(VI) extracted decreased and then increased again, while the extraction efficiency followed a slightly different trend. Overall mass transfer coefficients varied between 0.049 s and 0.312 s . © 2012 Elsevier B.V. All rights reserved.

Comments and Additional Work on “High-Pressure Volumetric Properties of Imidazolium-Based Ionic Liquids: Effect of the Anion”

This works follows a publication of our group in J. Chem. Eng. Data2007, 52, 2204–2211 presenting high temperature and pressure density data for five imidazolium-based ionic liquids. At this period, very few ionic liquid density data were available in the literature, especially at high pressure, and the uncertainty of published results was calculated with respect to the literature data available for three of the five ionic liquids studied. Since 2007, the ionic liquid density databank has largely increased. In this work, a comparison of our published data in J. Chem. Eng. Data2007, 52, 2204–2211, with more than 1800 high pressure data coming from the literature up to December 2011 is presented to assess the uncertainty of our published values. The claimed uncertainty is close to 0.31 % for all IL density data sets except in the case of the [C1C2Im][EtSO4], where the uncertainty is up to 1.1 %. Reported data in J. Chem. Eng. Data2007, 52, 2204–2211, for this particular ionic liquid cannot be used as a reference. For this ionic liquid, new density measurements of the same sample batch have been remeasured by using the same experimental technique, and new experimental data presented herein are clearly higher than our previous published results. A 1H NMR analysis of the sample has confirmed hydrolysis of the ethylsulfate anion to ethanol and hydrogenate anion which explains the differences observed between our density data and the literature.