1,3-alkylimidazolium

The room temperature conductivity data for a wide variety of ionic liquids are listed in Tables 3.6-3, 3.6-4, and 3.6-5. These tables are organized by the general type of ionic liquid. Table 3.6-3 contains data for imidazolium-based non-haloaluminate alkylimidazolium ionic liquids. Table 3.6-4 data for the haloaluminate ionic liquids, and Table 3.6-5 data for other types of ionic liquids. There are multiple listings for several of the ionic liquids in Tables 3.6-3-3.6-5. These represent measurements by different researchers and have been included to help emphasize the significant vari-... 

The reactive 1-acyl-3-alkylimidazolium species also plays a role in acylation of alcohols with carboxylic anhydrides or carboxylic acid chlorides using 1-substituted imidazoles as catalysts.[145] In this case the reactive species is formed in situ ... 

Because of the higher reaction rate, 7V(3)-alkylimidazolium-A ( 1 )-carboxylates or thiocarboxylates have often been used for the synthesis of carbamates and thiocarbamates by the azolide method instead of imidazole-iV-carboxylates. 

Depending on the acidity/coordination properties of the anion and on the reactivity of the cation (the possibility of carbene ligand formation from 1,3-di-alkylimidazolium salts is of particular importance here [49-56]), the ionic liquid... 

Hagiwara, R., Ito, Y. Room temperature ionic liquids of alkylimidazolium cations and fluoroanions, J. Fluorine Chem., 105(2), 2000, 221-227 Welton, T. Room-temperature Ionic Liquids. Solvents for Synthesis and Catalysis, Chem. Rev., 1999, 99, 2071-2084 ... 

While the reductive elimination is a major pathway for the deactivation of catalytically active NHC complexes [127, 128], it can also be utilized for selective transformations. Cavell et al. [135] described an interesting combination of oxidative addition and reductive elimination for the preparation of C2-alkylated imida-zohum salts. The in situ generated nickel catalyst [Ni(PPh3)2] oxidatively added the C2-H bond of an imidazolium salt to form a Ni hydrido complex. This complex reacts under alkene insertion into the Ni-H bond followed by reductive elimination of the 2-alkylimidazolium salt 39 (Fig. 14). Treatment of N-alkenyl functionalized azolium salts with [NiL2] (L = carbene or phosphine) resulted in the formation of five- and six-membered ring-fused azolium (type 40) and thiazolium salts [136, 137]. 

The Diels-Alder reaction between cyclopentadiene (1) and a series of dienophiles (2), Scheme 5, was examined in a typical alkylimidazolium ionic liquid at room temperature l-hexyl-3-methylimidazoliumtetrafluoroborate, [hmim][BF4]. ... 

Table 3.2-1 Specific conductivity data for non-haloaluminate alkylimidazolium-based ionic... 

The simplest alkylimidazolium ionic liquid 1,3-dimethylimidazolium chloride ([CiCiIm]Cl, numbering of the cation atoms is shown in Figure 2.2) and... 

Law, G., and Watson, P.R., Surface tension measurements of M-alkylimidazolium ionic liquids, Langmuir, 17, 6138-6141, 2001. 

In the last years, ILs have been applied as matrices for matrix-assisted laser desorption/ionization (MALDI) MS [42], thus expanding the use of MALDI. In Ref. 38 the suitability of alkylammonium- and alkylimidazolium salts of a-cyano-4-hydroxycinnamic acid was investigated as a MALDI matrix and at the same time as the additive of BGE. The alkylammonium salt produced better separation of phenolic compounds than the alkylimidazolium salt. The investigation suggests that it is possible to synthesize ILs suitable for electrophoretic analysis as well as for online MALDI-MS analysis. 

The easy handling of water- and air-stable ILs also enables their application to spectroscopic measurements. ILs have good solvahng properties and a high spectral transparency (the UV cut off wavelength of alkylimidazolium-based... 

Common ILs include ammonium, phosphonium, sulfonium, guanidinium, pyridinium, imidazolium, and pyrrolidinium cations. However, use of nomenclature vary among researchers. It is prefered to abbreviate throughout this book as [C C ,CJm], [C py], and [C C ,pyr] for the alkylimidazolium, pyridinium, and pyrrolidinium cations, respectively, where Im stands for imidazolium, py for pyridinium, and pyr for pyrrolidinium. The number of carbons in the N-alkyl chains are expressed by n, m, and z. 

With these studies, the alkylimidazolium-based salts became almost synonyms of ILs. Possibly, the most widely studied one is l-butyl-3-methy-limidazolium hexafluorophosphate, which is liquid at room temperature... 

Table 2.1 Standard ion transfer potentials of different A/yV-alkylimidazolium and l-butyl-4-methylpyridinium ionic liquid cations [29]...

The resulting extraordinary stability of NHC-metal complexes has been utilized in many challenging applications. However, an increasing number of publications report that the metal-carbene bond is not inert [30-38]. For example, the migratory insertion of an NHC into a ruthenium-carbon double bond [30], the reductive elimination of alkylimidazolium salts from NHC alkyl complexes [37] or the ligand substitution of NHC ligands by phosphines [36,38] was described. In addition, the formation of palladium black is frequently observed in applications of palladium NHC complexes, also pointing at decomposition pathways. 

Evans et al. also showed that the 1 1 mixture of BAN and (3, y-distearoyl-phos-photidylcholine (DSPC) gives a smectic A texture in the temperature range of 57.3 to 100°C [21]. This is the first notice of lyotropic lamellar liquid crystals formed in the ionic medium. Additionally, Seddon et al. [28] and Neve et al. [29] have described the long-chained A-alkylpyridinium or l-methyl-3-alkylimidazolium ions to display smectic liquid-crystalline phases above their melting points, when Cl or tetrachloro-metal anions like CoCl " and CuCl " are used as the counter ions. Lin et al. have also noted the liquid crystal behavior of 1-alkylimidazolium salts and the effect on the stereoselectivity of Diels-Alder reactions [30]. However, liquid crystals are classified as ionic liquid crystals (ILCs), and they are distinguished from liquid crystals that are dispersed in ionic liquids. Although the formation of micelles and liquid crystal phases in ionic liquids have been thus reported, there has been no mention of the self-assembly of developed nano-assemblies that are stably dispersed in ionic liquids. In the next section the formation of bilayer membranes and vesicles in ionic liquids is discussed. 

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