Ionic solvents

Certain amines, when linked to TPPTS, form ionic solvents liquid at quite low temperatures. Bahrman [33] used these ionic liquids as both ligands and solvents for the Rh catalyst for the hydroformylation of alkenes. In this otherwise interesting... 

Interestingly, the specific environment of the ionic solvent system appears to activate the chiral Ni-catalyst beyond a simple anion-exchange reaction. This becomes obvious from the fact that even the addition of a 100-fold excess of Fi[(CF3S02)2N] or Na[BF4] in pure, compressed CO2 produced an at best moderate activation of Wilke s complex in comparison to the reaction in ionic liquids with the corresponding counter-ion (e.g., 24.4 % styrene conversion with 100-fold excess of Fi[(CF3S02)2N], in comparison to 69.9 % conversion in [EMIM][(CF3S02)2N] under otherwise identical conditions). 

In conclusion, polymer electrolytes based on phosphazene backbone and containing ether side chains are, after complexation with alkali metal salts, among the highest ionically solvent-free polymer salt complexes, with conductivities in the order of 10" -10" S cm However, these conductivities are still below the value of 10 S cm" which is considered to be the minimum for practical applications. Therefore the design of new polyphosphazenes electrolytes with a higher conductivity and also a higher dimensional stability still remains a challenge for future researchers. 

The first application of ionic hquids for salen complexes dealt with the epoxidation of alkenes [14]. Jacobsen s Mn complex was immobilized in [bmimjlPFe] and different alkenes were epoxidized with aqueous NaOCl solution at 0 °C. As the ionic solvent sohdified at this temperature, dichloromethane was used as a cosolvent. The recychng procedure consisted of washing with water, evaporation of dichloromethane, and product extraction with hexane. The results (Table 3) were excellent and only a slow decay in activity and enantioselectivity was detected after several cycles. 

One of the important new directions in the study of addition reactions of organozinc compounds to aldehydes is the use of ionic liquids. Usually, application of these compounds in reactions with common organometallic reagents has a serious problem ionic solvents are usually reactive toward them, particularly Grignard and organolithium derivatives. It has been recently reported that carbonyl compounds react with allylzinc bromide formed in situ from allyl bromide and zinc in the ionic liquid 3-butyl-l-methylimidazolium tetrafluoroborate, [bmim][BF4].285 Another important finding is that the more reactive ZnEt2 alkylates aldehydes in a number of ionic liquids at room temperature.286 The best yields (up to 96%) were obtained in A-butylpyridinium tetrafluoroborate, [bpy][BF4] (Scheme 107). 

Additions of the Reformatsky-type reagents to aldehydes can also proceed in ionic solvents (Scheme 108).287 Three ionic liquids have been tested 8-ethyl-l,8-diazbicyclo[5,4,0]-7-undecenium trifluoromethanesulfonate ([EtDBU][OTf]), [bmim][BF4], and [bmim][PF6]. The reactions in the first solvent provided higher yields of alcohols 194 (up to 93%), although results obtained for two other ionic liquids were also comparable with those reported for conventional solvents. 

The benefits of using ionic compounds in microwave-enhanced reactions led us to explore the possibility of using ionic solvents i.e. ionic liquids, as donors for both deuterium and tritium. Whilst D20 is now relatively inexpensive and available at high isotopic enrichment, tritiated water is usually employed, for safety reasons, at low isotopic incorporation (we typically use HTO at 5 or 50 Ci mLT1 specific activity corresponding to 0.2-2% isotopic incorporation). This is a serious limitation when there is a need to provide compounds at high specific activity. 

The discovery of ionic liquids is proving a fertile field for researchers. Ionic solvents are revealing new mechanisms of reaction and enhancing our understanding of the molecular world. As well, their potential applications in both industry and the home have encouraged several companies, world-wide, to further explore and develop these unusual substances. 

Sun, J. MacFarlane, D. R. Forsyth, M. A new family of ionic liquids based on the l-alkyl-2-methylpyrrolinium cation, Electrochim. Acta, 2003, 48(12), 1707-1711 Fors3dh, S. Golding, J. MacFarlane, D. R. Forsyth, M. A-methyl-iV-alkylpyrrolidinium tetrafluoroborate salts ionic solvents and solid electrolytes, Electrochim. Acta, 2001, 46(10-11), 1753-1757 Golding, J. J. Macfarlane, D. R. Spiccia, L. et al. Weak intermolecular interactions in sulfonamide salts structure of 1-ethyl-2-methyl-3-benzylimidazolium bis[(trifluoromethyl)sulfonyl]amide, Chem. Commun., 1998, 1593-1594. 

The homogeneous catalytic reaction occurs in the multi-component liquid phase P. The chemical constituents of the liquid phase include H, e", atoms, ions, and molecules etc. which are dissolved/solvated in one or more molecular or ionic solvents. Primary examples of the ions and molecules present are the dissolved organic and organometallic reagents, intermediates and products. By definition, all the molecular and ionic species involved directly in the homogeneous catalysis are soluble in this liquid phase P. The set of all dissolved species in the phase will be denoted by Eq. (3). 

In a recent review, some positive attributes of ionic liquids in biocatalysis were discussed 273). An example was given, which compares the enzymatic performance of Pseudomonas cepacia lipase (PCL)-catalyzed reactions as a function of the solvent polarity in both organic and ionic solvents, as shown in Fig. 17. The PCL shows no activity in organic solvents in the polarity range of the ionic liquids, but it is active in the ionic liquids. 

Hydroxy- and 4-hydroxypyridines are in tautomeric equilibrium with isomers bearing a carbonyl group (Scheme 2.22). These are called 2- and 4-pyridones, respectively. The pyridone forms are favoured in ionic solvents and also in the solid state. 

TBHP and the molybdenum catalysts are soluble in imidazohiun-based RTlLs. The system becomes biphasic when the olefinic substrate is added. In all cases, the TOFs of the catalytic reactions are considerably lower with the ionic solvent than when performed without the ionic solvent (data reported in Table 9). This slower catalytic reaction may be due to dilution effects and phase transfer problems, especially with the olefin, which is quite insoluble in the RTIL. The conversion appears to be strongly temperature-dependent, as decreasing the temperature from 55 °C to 35 °C reduces the conversion by ca. 50% (entries 7 and 8, Table 9). With the dioxomolybdenum complexes 1 and 2, the epoxidation reaction proceeds with 100% selectivity (Table 9), whereas some diol is formed with the catalyst 3. 

Electrochemically characterized V(III) species are plentiful relative to the paucity of complexes which have been examined in lower oxidation states. Such species have been characterized in aqueous, nonaqueous, and ionic solvents. 

Extensive studies of the Heck reaction in low-melting salts have been presented by Hermann and Bohm [86]. Their results indicate that the application of ionic solvents offers clear advantages over that of commonly used organic solvents (e.g., DMF), especially for conversions of the commercially interesting chloroarenes. Additional activation and stabilization was observed with almost all catalyst systems tested. Among the ionic solvent systems investigated, molten [NBu4]Br (mp =... 

Margulis, C. J., Stern, H. A., and Berne, B. J., Computer simulation of a green chemistry room-temperature ionic solvent, /. Phys. Ghent. B., 106, 12017-12021, 2002. 

The use of two-phase catalysis in water or high-polar organic solvents is one of best approaches to clean catalytic hydrogenation (Hermann and Kohlpainter, 1993). Ionic solvents with a wide range of liquid phase (down to -81°C) based on l- -butyl-3-methylimidazolium cations can be used in these reactions. 

Observations Hydrophobic fluorinated pyridinium iodide ionic solvents lack sufficient... 

The equilibrium constants for these reactions are 8.9 x 10 8 (Eq. 17.11), 1 x 10-7 (Eq. 17.12), and 1 x 10"14 (Eq. 17.13) at 175°C [29]. As a consequence of Equation 17.13, there is a significant vapor pressure of A12C16 over acidic AlCl3-NaCl melt, making experimentation with this ionic solvent difficult. This is not a problem for the equimolar and NaCl(satd) melts. 

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