Ambient Temperature Ionic Liquids Research Articles

Oxidation of alcohols with hydrogen peroxide catalyzed by a new imidazolium ion based phosphotungstate complex in ionic liquid

A new catalyst based on imidazolium and tungstate ion (tris(imidazolium)-tetrakis(diperoxotungsto)phosphate (3-)) has been synthesized and characterized by FT-IR spectroscopy. An efficient and environmentally friendly procedure is described for the catalyst recycling and easy product isolation for the oxidation of alcohols with hydrogen peroxide catalyzed by imidazolium ion-based phosphotungstate complex in ambient-temperature ionic liquid.

Galvanostatic Deposition of Palladium-Gold Alloys in a Lewis Basic EMI ­ Cl ­ BF 4 Ionic Liquid

The electrodeposition of palladium-gold alloy was investigated in an ambient temperature ionic liquid electrolyte, 1-ethyl-3-methylimidazolium chloride tetrafluoroborate system containing palladium(II) and gold(I). Compact alloy deposits were obtained with galvanostatic electrolysis. The Pd content in the deposited Pd-Au alloy increases with increasing current density and the Pd mole fraction in the plating bath. For deposits obtained under mass-transport-limited current, the Pd content in the deposited alloys approximated the Pd mole fraction in the plating bath. The deposition temperature affected the homogeneity of the deposited Pd-Au solid solution. Data collected from X-ray powder diffraction experiments showed that Pd-Au alloys deposited at temperatures higher than 80°C were homogeneous Pd-Au solid solutions. The scanning electron micrographs of the deposits revealed nodular particles. The particle size decreased with increasing deposition current. © 2004 The Electrochemical Society. All rights reserved.

Deep eutectic solvents formed between choline chloride and carboxylic acids: versatile alternatives to ionic liquids.

Deep Eutectic Solvents (DES) can be formed between a variety of quaternary ammonium salts and carboxylic acids. The physical properties are significantly affected by the structure of the carboxylic acid but the phase behavior of the mixtures can be simply modeled by taking account of the mole fraction of carboxylic acid in the mixture. The physical properties such as viscosity, conductivity, and surface tension of these DES are similar to ambient temperature ionic liquids and insight into the cause of these properties is gained using hole-theory. It is shown that the conductivity and viscosity of these liquids is controlled by ion mobility and the availability of voids of suitable dimensions, and this is consistent with the fluidity of other ionic liquids and molten salts. The DES are also shown to be good solvents for metal oxides, which could have potential application for metal extraction.

Synthesis, Crystal Structures and Electrical Conductivities of the Ionic Liquid Compounds Butyldimethylimidazolium Tetrafluoroborate, Hexafluorophosphate and Hexafluoroantimonate

AbstractThe crystal structures of three very low‐melting ionic liquid (IL) salts containing the 1‐butyl‐2,3‐dimethylimidazolium cation and the fluoro anions BF4−, PF6− and SbF6− are reported. These are considered model compounds for ambient temperature ionic liquids, which are currently being explored as solvents for various types of synthetic reactions. All three compounds adopt significantly different structures in the solid state, highlighting the influence of counterion size in a series comprising a common cation. The crystal structures are discussed with respect to the possible existence of polar and non‐polar domains, which are considered to be involved with the solvation of polar and non‐polar substrates. The melting points of all three compounds are within the range 40−45 °C. A comparative measurement of conductivities of the molten salts in the vicinity of 20−50 °C has been made, including the new IL 1‐allyl‐2,3‐dimethylimidazolium tetrafluoroborate and the widely applied 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIMBF4). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Sustainable Epoxidation of Electron‐Poor Olefins with Hydrogen Peroxide in Ionic Liquids and Recovery of the Products with Supercritical CO2.

AbstractFor Abstract see ChemInform Abstract in Full Text.

N-donor complexes of palladium as catalysts for Suzuki cross-coupling reactions in ionic liquids

Palladium imidazole complexes have been used as catalyst precursors for the Suzuki cross-coupling reaction in 1-butyl-3-methylimidazolium-based ambient temperature ionic liquids. The system provides a stable, recyclable method for iodo- and bromoarenes. The preferred reaction conditions are explored and the effect of changing the ionic liquid components is investigated.

Sustainable Epoxidation of Electron‐Poor Olefins with Hydrogen Peroxide in Ionic Liquids and Recovery of the Products with Supercritical CO2

AbstractAn efficient procedure is described for the epoxidation of electron‐deficient olefins, in particular Vitamin K3 and analogues, with aqueous basic solutions of hydrogen peroxide in different ambient temperature ionic liquids (ILs) [bmim+][X−] {[bmim+] = 1‐butyl‐3‐methylimidazolium; [X−] = [BF4−], [CF3SO3−], [PF6−], [N(CF3SO2)2−]}. Various factors affecting epoxide yield (in the range 80−99%), reaction rate and reproducibility have been examined. The almost quantitative extraction of the epoxides from the reaction media has been obtained with supercritical CO2. The ionic liquid was then recovered and reused in subsequent cycles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Palladium-Catalyzed Suzuki Cross-Coupling Reactions in Ambient Temperature Ionic Liquids: Evidence for the Importance of Palladium Imidazolylidene Complexes

Palladium-catalyzed Suzuki cross-coupling reactions have been conducted in a range of ambient temperature ionic liquids. The ionic liquids give excellent reactivities for bromoarenes in addition to easy product isolation. The preferred reaction conditions are explored and the effect of changing the ionic liquid components is investigated. The in situ formation of mixed phosphine/imidazolylidene palladium complexes is demonstrated in all of the catalytically active solutions, but in none of the inactive solutions. Formation of 1,3-dialkyl-2-arylimidazolium salts is demonstrated, but it is also shown that these salts can act as a source of arene for the reaction; that is, both reductive elimination and oxidative addition of 1,3-dialkyl-2-arylimidazolium salts from/to the palladium are occurring. The implications of this for the use of ionic liquids as solvents for Suzuki reactions are discussed.

Manganeseporphyrin-catalyzed alkenes epoxidation by iodobenzene diacetate in a room temperature ionic liquid

Catalytic epoxidation of alkenes with iodobenzene diacetate by the manganeseporphyrin in environmentally benign and ambient temperature ionic liquid 1- n-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF 6) has been studied. The use of [bmim]PF 6 as the reaction medium brought definitive advantages over an organic catalytic phase: the reaction proceeded with high efficiency and the rate was much higher than that of in CH 2Cl 2; the ionic liquid–manganeseporphyrin system could be reused at least 12 times without losing activity. The mechanism of the reaction was also investigated.

Epoxidation of alkenes with hydrogen peroxide catalyzed by iron(iii) porphyrins in ionic liquidsElectronic supplementary information (ESI) available: experimental. See http://www.rsc.org/suppdata/cc/b2/b207072n/

An efficient procedure is described for catalyst recycling and easy product isolation in alkene epoxidation with hydrogen peroxide catalyzed by water-soluble iron(III) porphyrins in environmentally benign and ambient temperature ionic liquids.

Solvent-free sonochemical preparation of ionic liquids.

[reaction: see text] An ultrasound-assisted preparation of a series of ambient-temperature ionic liquids, 1-alkyl-3-methylimidazolium (AMIM) halides, which proceeds via efficient reaction of 1-methyl imidazole with alkyl halides/terminal dihalides under solvent-free conditions, is described.

Comparative kinetic investigations in ionic liquids using the MTO/peroxide system

The kinetics and thermodynamics of the reaction of methyltrioxorhenium (MTO) with hydrogen peroxide in ambient temperature ionic liquids have been studied. The rate constant for the formation of the diperoxorhenium complex, CH 3ReO(η 2-O 2) 2, from the monoperoxorhenium complex, CH 3ReO 2(η 2-O 2), and hydrogen peroxide in [bmim]NO 3 is 0.053±0.002 M −1 s −1. The equilibrium constants for the binding of two peroxide units have been determined in [emim]BF 4 to be K 1=110±28 and K 2=160±36. Similar rate constants and equilibrium constants are obtained in other water-miscible, dialkylimidazolium and alkylpyridinium ionic liquids. The values of the rate constants are highly dependent on the concentration of water in the solvent. These results indicate that the ionic liquids can behave like organic solvents and aqueous solutions of high salt concentrations.

Esterification reactions in ionic liquids. The efficient synthesis of ferrocenyl esters in the ionic liquids [bmim][BF4] and [bmim][PF6

The synthesis of ferrocenyl esters has been achieved using the DCC/DMAP protocol in the ambient temperature ionic liquids 1-butyl-3-methylimidazonium tetrafluoroborate ([bmim][BF4]) and 1-butyl-3-methylimidazonium hexafluorophosphate ([bmim][PF6]). Yields are very high and efficient recycling of solvent was achieved.

Quaternary ammonium zinc- or tin-containing ionic liquids: water insensitive, recyclable catalysts for Diels–Alder reactions

Synthetically important Diels–Alder reactions occur in high yield in novel Lewis acidic ambient temperature ionic liquids composed of choline chloride–MCl2 (1:2) (M = Zn or Sn). The liquids are not moisture-sensitive and after separation of the products they can be reused with no noticeable drop in activity.

Dispersions of Anatase in Ambient Temperature Ionic Liquids

1-Ethyl-3-methylimidazolium (EMI) tetrachloroaluminate (“basic melt,” AlCl3:EMICl ratio 0.94) and EMIBF4 were studied as two examples of ambient temperature ionic liquids (salts that are liquid at room temperature). Dispersions of graphite and anatase (300 nm in diameter particles) in these media are surprisingly stable considering the high (about 4 mol dm−3) ionic strength. Electrostatic interactions play a rather insignificant role in the stability of anatase in EMIBF4, with the absolute value of electrophoretic mobility of the particles not exceeding 3×10−10 m2V−1 s−1. The sign of electrophoretic mobility depends on the presence of traces of water in EMIBF4. The particles carry a positive electrokinetic charge in dehydrated EMIBF4, and in the presence of 1% water (added as liquid water or absorbed from the atmosphere) the sign is reversed to negative.

An Expeditious Solvent‐Free Route to Ionic Liquids Using Microwaves.

A microwave-assisted preparation of a series of ambient temperature ionic liquids, 1-alkyl-3-methylimidazolium (AMIM) halides, that proceeds via efficient reaction of 1-methylimidazole with alkyl halides/terminal dihalides under solvent-free conditions, is described.

Enzyme Catalysed Synthesis in Ambient Temperature Ionic Liquids

The activity of three different lipases, a glycosidase and a protease in ionic liquids has been studied. Ambient temperature ionic liquids are a new class of solvents that are nonvolatile and nonflammable and thus an interesting alternative to classical organic solvents. Monitoring the synthesis of a simple ester, all lipases were found to exhibit both excellent activity and stability in the non-polar ionic liquid 1-butyl-3-methylimidazohum hexaflurophosphate ([bmin][PF6], 1). Furthermore, β-galactosidase from E. coli and the Subtilisin protease SavinaseTM were both found to exhibit a hydrolytic activity in a 50% aqueous solution of the water-miscible ionic liquid 1-butyl-3-methyhmidazoUum tetra-fluoroborate ([bmin][BF4], 2) comparable to the activity observed in 50% aqueous solutions of ethanol and acetonitrile.

Novel Ambient Temperature Ionic Liquids for Zinc and Zinc Alloy Electrodeposition

SUMMARYThis work shows that novel ambient temperature ionic liquids can be produced from substituted quaternary ammonium salts and some metal salts. The ionic liquids are sufficiently conducting to allow electrochemical investigations to be carried out. Data on the electrochemical reduction of the metal ions is presented together with information on the deposit morphology of Zn, and Zn/Sn and Zn/Co alloys. The low cost and low toxicity of the ionic liquids makes possible their use for large-scale metal finishing applications.

An expeditious solvent-free route to ionic liquids using microwaves

A microwave-assisted preparation of a series of ambient temperature ionic liquids, 1-alkyl-3-methylimidazolium (AMIM) halides, that proceeds via efficient reaction of 1-methylimidazole with alkyl halides/terminal dihalides under solvent-free conditions, is described.

Moisture Stable Ambient Temperature Ionic Liquids: Solvents for the New Millennium. 1. The Heck Reaction

In this paper we report examples of the Heck reaction in the new moisture stable ambient temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6). We have found that the yield of product is comparable with Heck reactions carried out in DMF, the conventional solvent for this reaction, and that the ionic liquid/catalyst mixture can be recycled several times.