Preparation of novel,moisture-stable,Lewis-acidic ionic liquids containing quaternary ammonium salts with functional side chains

A range of novel, moisture-stable, Lewis-acidic ionic liquids has been prepared by mixing appropriate molar ratios of MCl2 (M = Zn and/or Sn) and quaternary ammonium salts of formula [Me3NC2H4Y]Cl (Y = OH, Cl, OC(O)Me, OC(O)Ph); the influence of substituent Y and metal M on the physical properties of the melts has been investigated.     

Polychloride monoanions from [Cl3]- to [Cl9]- : a Raman spectroscopic and quantum chemical investigation

Polychloride monoanions stabilized by quaternary ammonium salts are investigated using Raman spectroscopy and state-of-the-art quantum-chemical calculations. A regular V-shaped pentachloride is characterized for the [N(Me)(4)][Cl(5)] salt, whereas a hockey-stick-like structure is tentatively assigned for [N(Et)(4)][Cl(2)???Cl(3)(-)]. Increasing the size of the cation to the quaternary ammonium salts [NPr(4)](+) and [NBu(4)](+) leads to the formation of the [Cl(3)](-) anion. The latter is found to be a pale yellow liquid at about 40 °C, whereas all the other compounds exist as powders. Further to these observations, the novel [Cl(9)](-) anion is characterized by low-temperature Raman spectroscopy in conjunction with quantum-chemical calculations.     

Chemoselective reduction of aromatic nitro and azo compounds in ionic liquids using zinc and ammonium salts

Nitroarenes were chemoselectively reduced to the corresponding amines using zinc and aqueous ammonium salts in ionic liquids as a safe and recyclable reaction medium. Our results specify the effect of ammonium salts in the process; the combination of Zn/NH₄Cl in [bmim][PF₆] or Zn/HCO₂NH₄ in [bmim][BF₄] were the suitable conditions for the reduction of nitroarenes. Azobenzenes were also smoothly reduced to hydrazobenzenes with Zn/HCO₂NH₄ (aq.) in recyclable [bmim][BF₄] without any over reduction to the corresponding anilines.     

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.     

Hydrophilic quaternary ammonium type ionic liquids. Systematic study of the relationship among molecular structures, osmotic pressures, and water-solubility

This Letter examines the relationship between the structures of ionic liquids and their water-solubility or osmotic pressure with a number of synthesized quaternary ammonium type ionic liquids and organic salts containing a hydroxyl group as hydrophilic substituted groups on ammonium group cations, and bromide or methylsulfonate as anions. The study found a linear relation between the amount and osmotic pressure of the water-soluble ionic liquids synthesized here, strongly indicating that these water-soluble ionic liquids are perfectly ionized in water like inorganic salts with small diameter ions.     

Do all ionic liquids need organic cations? Characterisation of [AlCl2·nAmide]+ AlCl4(-) and comparison with imidazolium based systems

The addition of a simple amide to AlCl(3) causes the formation of a liquid of the form [AlCl(2)·nAmide](+) AlCl(4)(-). The material thus produced is liquid over a wide temperature range, is relatively insensitive to water and has the properties of an ionic liquid. This ionic liquid is shown to be a suitable medium for the acetylation of ferrocene and the electrodeposition of aluminium and demonstrated that quaternary ammonium cations are not always needed to form ionic liquids.     

Synthesis and characterization of ionic liquids incorporating the nitrile functionality

A series of imidazolium salts with the nitrile functional group attached to the alkyl side chain, viz. [CnCNmim][X] (where CnCNmim is the 1-alkylnitrile-3-methylimidazolium cation and Cn= (CH2)(n), n = 1-4; X = Cl, PF(6), and BF(4)) and [C3CNdmim][X] (where CnCNdmim is the 1-alkylnitrile-2,3-dimethylimidazolium cation and C(n) = (CH2)(n), n = 3; X = Cl, PF(6), and BF(4)), have been prepared and characterized using spectroscopic methods. The majority of the nitrile-functionalized imidazolium salts can be classed as ionic liquids since they melt below 100 degrees C. Four of the imidazolium salts have been characterized in the solid state using single-crystal X-ray diffraction analysis to reveal an extensive series of hydrogen bonds between H atoms on the cation and the anion. The relationship between the solid-state structure and the melting point is discussed. Key physical properties (density, viscosity, and solubility in common solvents) of the low melting ionic liquid have been determined and are compared with those of the related 1-alkyl-3-methylimidazolium and 1-alkyl-2,3-dimethylimidazolium ionic liquids. It was envisaged that these ionic liquids could act as both solvent and ligand for catalyzed reactions, and this application is demonstrated in hydrogenation reactions, which show that retention of the catalyst in the ionic liquid during product extraction is extremely high.     

Eutectic-based ionic liquids with metal-containing anions and cations

Eutectic mixtures of zinc chloride and donor molecules such as urea and acetamide are described and it is proposed that these constitute a new class of ionic liquids. FAB-MS analysis shows that the liquids are made up of metal-containing anions and cations in which the donor is coordinated to the cation. Data on the viscosity, conductivity, density, phase behaviour and surface tension are presented and these are shown to be significantly different to other related ionic liquids that incorporate quaternary ammonium salts. The conductivity and viscosity are comparable with other ionic liquids and the data fit well to the Hole theory model recently proposed.     

Low-melting, low-viscous, hydrophobic ionic liquids: aliphatic quaternary ammonium salts with perfluoroalkyltrifluoroborates

A novel class of low-melting, hydrophobic ionic liquids based on relatively small aliphatic quaternary ammonium cations ([R(1)R(2)R(3)NR](+), wherein R(1), R(2), R(3) = CH(3) or C(2)H(5), R = n-C(3)H(7), n-C(4)H(9), CH(2)CH(2)OCH(3)) and perfluoroalkyltrifluoroborate anions ([R(F)BF(3)](-), R(F) = CF(3), C(2)F(5), n-C(3)F(7), n-C(4)F(9)) have been prepared and characterized. The important physicochemical and electrochemical properties of these salts, including melting point, glass transition, viscosity, density, ionic conductivity, thermal and electrochemical stability, have been determined and comparatively studied with those based on the corresponding [BF(4)](-) and [(CF(3)SO(2))(2)N](-) salts. The influence of the structure variation in the quaternary ammonium cation and perfluoroalkyltrifluoroborate ([R(F)BF(3)](-)) anion on the above physicochemical properties is discussed. Most of these salts are liquids at 25 degrees C and exhibit low viscosities (58-210 cP at 25 degrees C) and moderate conductivities (1.1-3.8 mS cm(-1)). The electrochemical windows of these salts are much larger than those of the corresponding 1,3-dialkyimidazolium salts. Additionally, a number of [R(F)BF(3)](-) salts exhibit plastic crystal behavior.     

Review of ionic liquids with fluorine-containing anions

Interest in ionic liquids has grown markedly in recent years. The syntheses, characterization and properties of quaternary alkyl-substituted ammonium, imidazolium, triazolium and pyridinium salts with a variety of fluorine-containing anions have been studied in detail; however, ionic liquids with other cations and anions continue to be discovered. This review is limited to the literature from 2000 to 2005 dealing with ionic liquids with fluorine-containing anions.     

Dynamic Covalent Chemistry of Nucleophilic Substitution Component Exchange of Quaternary Ammonium Salts

Dynamic covalent libraries (DCLs) of quaternary ammonium cations were set up by reversible nucleophilic substitution (S_N2′ and S_N2) exchange reactions of ammonium salts and tertiary amines. The reactions were conducted at 60 °C to generate thermodynamically and kinetically controlled mixtures of quaternary ammonium compounds and tertiary amines, and were accelerated by using iodide as a nucleophilic catalyst. Microwave irradiation was used to assist the exchange reaction between the pyridinium salts and pyridine derivatives. Finally, experiments towards the generation of dynamic ionic liquids were performed. The results of this study pave the way for the extension of dynamic combinatorial chemistry to nucleophilic substitution reactions.     

Validation of speciation techniques: a study of chlorozincate(II) ionic liquids

The speciation of chlorozincate(II) ionic liquids, prepared by mixing 1-octyl-3-methylimidazolium chloride, [C(8)mim]Cl, and zinc(II) chloride in various molar ratios, χ(ZnCl(2)), was investigated using Raman spectroscopy and differential scanning calorimetry; the Gutmann acceptor number, which is a quantitative measure of Lewis acidity, was also determined as a function of the composition. These results were combined with literature data to define the anionic speciation; in the neat liquid phase, the existence of Cl(-), [ZnCl(4)](2-), [Zn(2)Cl(6)](2-), [Zn(3)Cl(8)](2-), and [Zn(4)Cl(10)](2-) anions was confirmed. From two chlorozincate(II) ionic liquids with [C(2)mim](+) cations (χ(ZnCl(2)) = 0.33 and χ(ZnCl(2)) = 0.50), crystals have been obtained, revealing the structures of [C(2)mim](2)[ZnCl(4)] and [C(2)mim](2)[Zn(2)Cl(6)] forming three-dimensional hydrogen-bond networks. The compound [C(2)mim](2){Zn(4)Cl(10)} was crystallized from the χ(ZnCl(2)) = 0.75 composition, showing an open-framework structure, with the first example of zinc in a trigonal-bipyramidal chloride coordination. Reinvestigation of the electrospray ionization mass spectrometry of these systems demonstrated that it is an unreliable technique to study liquid-phase speciation.     

Copper(I)-containing ionic liquids for high-rate electrodeposition

New metal-containing ionic liquids [Cu(CH(3)CN)(n)][Tf(2)N] (n=2, 4; Tf(2)N=bis(trifluoromethylsulfonyl)- amide) have been synthesised and used as a non-aqueous electrolyte for the electrodeposition of copper at current densities greater than 25 A dm(-2). The tetrahedral copper(I)-containing cation in [Cu(CH(3)CN)(4)][Tf(2)N] is structurally analogous to quaternary ammonium and phosphonium ionic liquids and overcomes problems of metal solubility and mass transport. Two CH(3)CN ligands are removed at elevated temperatures to give [Cu(CH(3)CN)(2)][Tf(2)N], which can be used as a concentrated non-aqueous electrolyte. The structural and electrochemical characterisation of these compounds is described herein.     

Nitrile-functionalized pyridinium ionic liquids: synthesis, characterization, and their application in carbon-carbon coupling reactions

A series of relatively low-cost ionic liquids, based on the N-butyronitrile pyridinium cation [C(3)CNpy](+), designed to improve catalyst retention, have been prepared and evaluated in Suzuki and Stille coupling reactions. Depending on the nature of the anion, these salts react with palladium chloride to form [C(3)CNpy](2)[PdCl(4)] when the anion is Cl(-) and complexes of the formula [PdCl(2)(C(3)CNpy)(2)][anion](2) when the anion is PF(6)(-), BF(4)(-), or N(SO(2)CF(3))(2)(-). The solid-state structures of [C(3)CNpy]Cl and [C(3)CNpy](2)[PdCl(4)] have been established by single-crystal X-ray diffraction. The catalytic activity of these palladium complexes following immobilization in both N-butylpyridinium and nitrile-functionalized ionic liquids has been evaluated in Suzuki and Stille coupling reactions. All of the palladium complexes show good catalytic activity, but recycling and reuse is considerably superior in the nitrile-functionalized ionic liquid. Inductive coupled plasma spectroscopy reveals that the presence of the coordinating nitrile moiety in the ionic liquid leads to a significant decrease in palladium leaching relative to simple N-alkylpyridinium ionic liquids. Palladium nanoparticles have been identified as the active catalyst in the Stille reaction and were characterized using transmission electron microscopy.     

氯铝酸室温离子液体介质中Blanc氯甲基化反应的研究

在卤化1－烷基吡啶，1－甲基－3－烷基咪唑季胺盐和盐酸三甲胺与无水 AlCl3构成的氯铝酸室温离子液体反应介质中，尝试了苯及其衍生物和氯甲醚的 Blanc氯甲基化反应。结果表明底物的不同对反应有较大影响，苯与氯甲醚反应主 要生成氯甲基化产物，而烷基苯与氯甲醚反应则主要生成二苯基甲烷衍生物。反应 具有适中至高的转化率和选择性，依据底物的不同，反应结束后可以和离子液体系 分层，便于产物分离。氯铝酸离子液体具有一定的重复使用性。     

Carboxyl-functionalized task-specific ionic liquids for solubilizing metal oxides

Imidazolium, pyridinium, pyrrolidinium, piperidinium, morpholinium, and quaternary ammonium bis(trifluoromethylsulfonyl)imide salts were functionalized with a carboxyl group. These ionic liquids are useful for the selective dissolution of metal oxides and hydroxides. Although these hydrophobic ionic liquids are immiscible with water at room temperature, several of them form a single phase with water at elevated temperatures. Phase separation occurs upon cooling. This thermomorphic behavior has been investigated by (1)H NMR, and it was found that it can be attributed to the temperature-dependent hydration and hydrogen-bond formation of the ionic liquid components. The crystal structures of four ionic liquids and five metal complexes have been determined.     

季膦-磷钨酸室温离子液体的合成及光催化降解罗丹明B

以不同摩尔比的磷钨酸与烷基取代季膦盐为原料合成了一系列磷钨酸类离子液体,并使用DSC和IR对系列离子液体进行了表征。 结果表明,[P(C14H29)(C6H13)3]-磷钨酸系列离子液体为室温离子液体,磷钨酸根保留了Keggin结构。 进一步研究了在可见光照射下,以所制备的磷钨酸季膦盐离子液体为催化剂催化降解罗丹明B染液。 以脱色率和COD来表征染料的降解效果,分别探讨了离子液体中阳离子碳链长度、催化剂用量、光照时间和罗丹明B的初始浓度等因素对光降解罗丹明B的影响。 结果表明,其中[P(C14H29)(C6H13)3]3-PW12O40离子液体的催化效果最好,在催化剂用量为0.3 g时,3 h内50 mL 8.35×10-5 mol/L罗丹明B的降解率可达到95%以上,催化剂重复使用5次后,脱色率仍可达到97%以上。     

Efficient catalytic synthesis of optically active cyclic carbonates via coupling reaction of epoxides and carbon dioxide

Chiral Co(salen) complexes bearing the Lewis acid of group 13 can efficiently catalyze the reactions of carbon dioxide with epoxides in the presence of catalytic amounts of alkali metal salts, quaternary ammonium halide or ionic liquids. They exhibited excellent activity for producing enantiomerically enriched cyclic carbonates.     

Photophysical properties of Kuratowski-type coordination compounds [M(II)Zn4Cl4(Me2bta)6] (M(II) = Zn or Ru) featuring long-lived excited electronic states

The syntheses of Kuratowski-type pentanuclear clusters featuring {MZn(4)Cl(4)} cores (M(II) = Ru or Zn) that incorporate triazolate ligands are described. The coordination compounds are characterized by single-crystal X-ray diffraction, X-ray powder diffraction (XRD), FTIR- and UV-vis spectroscopy. [Ru(II)Zn(4)Cl(4)(Me(2)bta)(6)]·2DMF (Me(2)bta(-) = 5,6-dimethyl-1,2,3-benzotriazolate) (1) crystallizes in the cubic system, while [Zn(5)Cl(4)(ta)(6)] (ta(-) = 1,2,3-triazolate) (3) crystallizes in the tetragonal system. Both compounds feature structurally similar cluster topologies in which the central octahedrally coordinated metal ion is coordinated to six triazolate ligands. Each triazolate ligand is coordinated with two zinc ions (μ(3)-bridging mode), leading altogether to a pentanuclear cluster of T(d) point group symmetry. Photophysical investigations reveal that compound [Zn(5)Cl(4)(Me(2)bta)(6)]·2DMF (2) shows a short-lived excited electronic state, which can be populated with high quantum yield. The isostructural compound [Ru(II)Zn(4)Cl(4)(Me(2)bta)(6)]·2DMF (1), on the other hand, shows a long-lived photoexcited state, owing to an internal singlet to triplet conversion of the electronic states, as revealed by time-resolved fluorescence spectroscopy. Insights gained from these studies open up novel design strategies towards photocatalytically active metal-organic frameworks incorporating photoactive Kuratowski-type secondary building units such as MFU-4 (Metal-Organic Framework Ulm University-4).     

The first ionothermal synthesis of a germanium phosphate with one-dimensional chain-like structure

A novel germanium phosphate with a chain-like framework constructed from GeO(4)N(2) octahedra and PO(4) tetrahedra, [NH(4)](2)[Ge(NH(3))(2)(PO(4))(2)]·0.38H(2)O, was first synthesized via in situ decomposition of urea from ionic eutectic mixtures comprising urea and quaternary ammonium salts.