Methylimidazolium hexafluorophosphate

Figure 4.2-1 shows the calculated ab initio molecular structure of the ionic liquid [BMIM][PFg] (l-butyl-3-methylimidazolium hexafluorophosphate). 

Scheme 6.93) [192]. Using either of the two solvent systems, all studied cycloaddition reactions were completed in less than 1 min upon microwave irradiation at 50 °C employing 3 mol% of the catalyst. An additional advantage of using the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) as solvent is that it facilitates catalyst recycling. 

Inter- and intramolecular hetero-Diels-Alder cycloaddition reactions in a series of functionalized 2-(lH)-pyrazinones have been studied in detail by the groups of Van der Eycken and Kappe (Scheme 6.95) [195-197]. In the intramolecular series, cycloaddition of alkenyl-tethered 2-(lH)-pyrazinones required 1-2 days under conventional thermal conditions involving chlorobenzene as solvent under reflux conditions (132 °C). Switching to 1,2-dichloroethane doped with the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) and sealed-vessel microwave technology, the same transformations were completed within 8-18 min at a reaction temperature of 190 °C (Scheme 6.95 a) [195]. Without isolating the primary imidoyl chloride cycloadducts, rapid hydrolysis was achieved by the addition of small amounts of water and subjecting the reaction mixture to further microwave irradia-... 

In 2002, Leadbeater and Torenius reported the base-catalyzed Michael addition of methyl acrylate to imidazole using ionic liquid-doped toluene as a reaction medium (Scheme 6.133 a) [190], A 75% product yield was obtained after 5 min of microwave irradiation at 200 °C employing equimolar amounts of Michael acceptor/donor and triethylamine base. As for the Diels-Alder reaction studied by the same group (see Scheme 6.91), l-(2-propyl)-3-methylimidazolium hexafluorophosphate (pmimPF6) was the ionic liquid utilized (see Table 4.3). Related microwave-promoted Michael additions studied by Jennings and coworkers involving indoles as heterocyclic amines are shown in Schemes 6.133 b [230] and 6.133 c [268], Here, either lithium bis(trimethylsilyl)amide (LiHMDS) or potassium tert-butoxide (KOtBu) was em-... 

The substrates were admixed with 50 mol% of copper(I) chloride and small amounts of l-(2-propyl)-3-methylimidazolium hexafluorophosphate (pmimPF6) in dioxane. The mixture was heated to 110 °C within 2 min and kept at this reaction temperature for an additional 1 min. After cooling to room temperature, the product was rapidly released from the polymer support employing 20% trifluoroacetic acid (TFA) in dichloromethane, furnishing the corresponding bis-TFA salt in moderate yield. 

The microwave-assisted thionation of amides has been studied by Ley and coworkers using a polymer-supported thionating reagent [115]. This polymer-supported amino thiophosphate serves as a convenient substitute for its homogeneous analogue in the microwave-induced rapid conversion of amides to thioamides. Under microwave conditions, the reaction is complete within 15 min, as opposed to 30 h by conventional reflux in toluene (Scheme 7.95). The reaction has been studied for a range of secondary and tertiary amides and GC-MS monitoring showed that it proceeded almost quantitatively. More importantly, this work was the first incidence of the use of the ionic liquid l-ethyl-3-methylimidazolium hexafluorophosphate... 

Recently, Dupont and coworkers described the use of room-temperature imi-dazolium ionic liquids for the formation and stabilization of transition-metal nanoparticles. The potential interest in the use of ionic liquids is to promote a bi-phasic organic-organic catalytic system for a recycling process. The mixture forms a two-phase system consisting of a lower phase which contains the nanocatalyst in the ionic liquid, and an upper phase which contains the organic products. Rhodium and iridium [105], platinum [73] or ruthenium [74] nanoparticles were prepared from various salts or organometallic precursors in dry 1-bu-tyl-3-methylimidazolium hexafluorophosphate (BMI PF6) ionic liquid under hydrogen pressure (4 bar) at 75 °C. Nanoparticles with a mean diameter of 2-3 nm... 

C. 1- Butyl-3-methylimidazolium hexafluorophosphate. A 1-L, one-necked, round-bottomed flask (Note 13) is charged with 65.6 g (0.37 mol, 1 equiv) of 1- butyl-3-methylimidazolium chloride, and 69.3 g (0.37 mol, 1 equiv) of potassium hexafluorophosphate (Note 19) in 70 ml of distilled water. The reaction mixture is stirred at room temperature for 2 hr affording a two-phase system. The organic phase is washed with 3 X 50 mL of water and dried under reduced pressure (0.1 mbar, 0.001 mm). Then 100 ml of dichloromethane and 35 g of anhydrous magnesium sulfate are added. After 1 hr, the suspension is filtered and the volatile material is removed under reduced pressure (0.1 bar, 0. 1 mm) at 30°C for 2 hr to afford 86.4 g (0.29 mol, 81%) of 1- butyl-3-methylimidazolium hexafluorophosphate as alight yellow viscous liquid, mp 10°C (Notes 20 and 21). 

Butyl-3-methylimidazolium hexafluorophosphate IH-lmidazolium, 1-butyl-3-methyl-, hexafluorophosphate(l-) (13) (174501-64-5)... 

The reaction conditions were room temperature and pressure and the IL was developed from l-butyl-3-methylimidazolium hexafluorophosphate using 1-4 mol% Pd(OAc)2, 1 mol % Lewis acid, and 0.5 mL of IL. The reaction times were from 2.5 to 4.5 h. The Lewis acids were chosen from the following Cu(OTf)2, Cu(CF3C02)2, Zn(OTf)2, and In(OTf)3. 

Three ionic liquids were purchased from Aldrich l-butyl-3-methylimidazolium chloride, l-butyl-3-methylimidazolium hexafluorophosphate and l-butyl-3-methylimidazolium tetrafluoroborate. Homogeneous Co (II) catalyst precursors used in our experiments include Co(BF4)2, Co(OAc)2, and Co(C104)2 each of which have high solubilities in above ionic liquids. High surface area catalyst supports Si02 and AI2O3 were obtained from Davison and Engelhard, respectively. 

The advantage of the stoichiometric technique is that it is extremely simple. Care has to be taken to remove all gases dissolved in the IL sample initially, but this is easily accomplished because one does not have to worry about volatilization of the IL sample when the sample chamber is evacuated. The disadvantage of this technique is that it requires relatively large amounts of ILs to obtain accurate measurements for gases that are only sparingly soluble. At ambient temperature and pressure, for instance, 10 cm of l-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) would take up only 0.2 cm of a gas with a Henry s law constant of... 

Morrow, T.l. and Maginn, E.J., Molecular dynamics study of the ionic liquid l-n-butyl-3-methylimidazolium hexafluorophosphate, ]. Phys. Chem. B, 106, 12807,2002. 

Zafarani-Moattar, M.T. and Shekaari, H. Volumetric and speed of sound of ionic liquid, l-butyl-3-methylimidazolium hexafluorophosphate with acetonitrile and methanol at T = (298.15 to 318.15) K, /. Chem., Eng. Data, 50,1694,2005. Wang, J. et al.. Excess molar volumes and excess logarithm viscosities for binary mixtures of the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate with some organic solvents, /. Solution Chem., 34, 585, 2005. 

Dzyuba, S.V. and Bartsch, R.A., Influence of structural variation in l-alkyl(aralkyl)-3-methylimidazolium hexafluorophosphate and bis(trifluoro methylsulfonyhimides on physical properties of the ionic liquids, Chem. Phys. Chem., 3,161,2002. 

Domariska, U. and Marciniak A., Solubility of l-alkyl-3-methylimidazolium hexafluorophosphate in hydrocarbons, ]. Chem. Eng. Data, 48, 451,2003. 

Swatloski, R.P., Holbrey, J.D., and Rogers, R.D., Ionic liquids are not always green hydrolysis of l-butyl-3-methylimidazolium hexafluorophosphate. Green Chem., 5, 361-363, 2003. 

Planeta, J. and Roth, M., Partition coefficients of low-volatility solutes in the ionic liquid l-M-butyl-3-methylimidazolium hexafluorophosphate-supercritical CO2 system from chromatographic retention measurements,. Phys. Chem. B, 108, 11244-11249, 2004. 

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