Dialkylimidazolium bis

Quek S K, LyapkaloHuynh 1 M, Huynh H V. Synthesis and properties of NdV -dialkylimidazolium bis(nonafluorobutane-l-sulfonyl)imides A new subfamily of ionic liquids. Tetrahedron. 2006. 62, 3137-3145. 

Tables The melting points of some 1,3-dialkylimidazolium bis(trifluoromethyl)imide salts [7], ...

Ionic liquids have recently appeared as clean alternatives to classical organic solvents for a wide variety of biochemical processes due to their unique properties [22-26]. Ionic liquids are organic salts which are liquid close to room temperature. They normally consist of an organic cation (e.g. dialkylimidazolium, tetraalkylam-momium) and a polyatomic inorganic cation (e.g. hexafluorophosphate, tetrafluoroborate, bis(trifluoromethylsulphonyl)imide) (Fig. 8.2). 

A large variety of ILs of high purity with water content below lOOppm and halide content below lOppm are now available commercially. These include numerous iV-alkylpyridinium, 7V,7V -dialkylimidazolium, alkylammonium and alkylphosphonium salts, covalent hydrophobic ILs (e.g. l,2-dimethyl-3-propyliniidazolium bis(trifluoromethylsulfonyl)imide, task-specific ILs, Bronsted acidic ILs (e.g. 3-[triphenylphosphonio]propane-l-sulfonic acid tosylate), nitrile-fiinction sed ILs, perfluorinated ILs (e.g. tetrabutylammonium nonafluorobutane sulfonate, BASF Basionics (e.g. 1,2,3-trimethylimidazolium methyl sulfate), and TOMATS for heavy metal extraction (e.g. methyltrioctylammonium thiosalicylate)... 

All 1,3-dialkylimidazolium ILs reported to date are hygroscopic, and their miscibility with water is largely controlled by the nature of the anion. While those salts containing the nitrate, chloride and perchlorate anions are usually miscible with water in all proportions, those associated with hexafluorophosphate and bis(tri-fluoromethane) sulfonylamidate anions are almost completely immiscible with water [93]. Interestingly, the miscibility with water of those containing the tetraf lu-oroborate anion is temperature dependent (Fig. 3.5-7) [36]. It is also known that an increase of the N-alkyl chain lengths increases the hydrophobicity for a series of 1-alkyl-3-methylimidazolium hexafluorophosphate ILs [94] The miscibility of water with ILs can be increased by the addition of short-chain alcohols [95] or diminished by the addihon of salts (salting-out effect) [96]. 

Finally, a third way of ligand formation from a 1,3-dialkylimidazolium cation has been described by Dupont and coworkers [57]. They investigated the hy-drodimerization/telomerization of 1,3-butadiene with paUadium(ii) compounds in [BMIM][Bp4] and described the activation of the catalyst precursor complex [BMIM]2[PdCU] via a palladium(IV) compound, which is formed by oxidative addition of the imidazolium with cleavage of the C-N bond of the [BMIM]+ ion leading to dichloro-bis(methylimidazole)-palladium (Scheme 5.3-5). However, this reaction was only observed in the presence of water. 

Researchers have also prepared and studied nonaqueous RMs where water has been replaced by polar solvents that possess relatively high dielectric constants and that are immiscible with the continuous nonpolar solvent [6].These nonaqueous RMs have attracted interest from both fundamental and practical perspectives [48-69]. As reaction media, these RMs are particularly attractive for water-sensitive reactions [70]. In this sense, ionic liquids (ILs) emerge as a powerful and attractive alternative to conventional molecular organic solvents [71-76], and they have received much attention as a class of neoteric solvents [71-83]. The most commonly used ILs are based on A,A -dialkylimidazolium cations, especially l-butyl-3-methyUmidazohuin, [bmim], with different anions such as tetrafluoroborate [BFJ or bis(trifluoromethylsulfonyl) imide [Tf N]" (see structures in Fig. 14.3). Recent studies on RMs with an IL... 

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