Tetrafluoroborate ionic liquid

The authors correlate the observed catalytic activity with the solubility of the 1,3-butadiene feedstock in the ionic liquid, which was found to be twice as high in the tetrafluoroborate ionic liquid as in the corresponding hexafluorophosphate system. It is noteworthy that the same reaction in a monophasic systems with toluene as the solvent was found to be significantly less active (TOF = 240 h ... 

The electrodeposition of Ag has also been intensively investigated [41 3]. In the chloroaluminates - as in the case of Cu - it is only deposited from acidic solutions. The deposition occurs in one step from Ag(I). On glassy carbon and tungsten, three-dimensional nucleation was reported [41]. Quite recently it was reported that Ag can also be deposited in a one-electron step from tetrafluoroborate ionic liquids [43]. However, the charge-transfer reaction seems to play an important role in this medium and the deposition is not as reversible as in the chloroaluminate systems. 

Scheme 4.2 The preparation of imidazolium tetrafluoroborate ionic liquids (where R is an alkyl group)...

In the ideal biphasic hydrogenation process, the substrate will be more soluble or partially soluble in the immobilization solvent and the hydrogenation product will be insoluble as this facilitates both reaction and product separation. Mixing problems are sometimes encountered with biphasic processes and much work has been conducted to elucidate exactly where catalysis takes place (see Chapter 2). Clearly, if the substrates are soluble in the catalyst support phase, then mixing is not an issue. The hydrogenation of benzene to cyclohexane in tetrafluoroborate ionic liquids exploits the differing solubilities of the substrate and product. The solubility of benzene and cyclohexane has been measured in... 

Holbrey, J. D. Seddon, K. R. The phase behaviour of l-alkyl-3-methylimidazolium tetrafluoroborates ionic liquids and ionic liquid crystals, J. Chem. Soc., Dalton Trans., 1999, 2133-2139. 

Putilova ES, Troitskii NA, Zlotin SG (2005) Reaction of aromatic aldehydes with beta-dicarbonyl compounds in a catalytic system piperidinium acetate - l-butyl-3-methylimida-zolium tetrafluoroborate ionic liquid. Russ Chem Bull 54 1233-1238... 

Mutelet, F. and Jaubert, J-N., Measurements of activity coefficients at infinite dilution in l-hexadecyl-3-methylimidazolium tetrafluoroborate ionic liquid, /. Chem Thermodyn., 39,1144,2007. 

Xiao, L., and Johnson K.E., Electrochemistry of l-butyl-3-methyl-lH-imidazo-lium tetrafluoroborate ionic liquid,. Electrochem. Soc., 150, E307-E311, 2003. 

Kaliszan, R., Marszatt, M. R, Markuszewski, M. J., B czek, T., and Pernak, J., Suppression of deleterious effects of free silanols in liquid chromatography by imidazolium tetrafluoroborate ionic liquids, J. Chromatogr. A, 1030, 263-271, 2004. 

Heimer, N. E., Del Sesto, R. E., and Carper, W. R., Evidence for spin diffusion in a H,H-NOESY study of imidazolium tetrafluoroborate ionic liquids, Magn. Reson. Chem., 42, 71-75,2004. 

Recently, our group described in collaboration with Tkatchenko et al. the Pd-catalyzed dimerisation of methylacrylate(MA) using a tetrafluoroborate ionic liquid as catalyst solvent (Scheme 6) [54]. 

Scheme 6. Pd-catalyzed dimerisation of methylacrylate using a tetrafluoroborate ionic liquid as catalyst solvent.

Palladium is employed in a number of industrial applications and fundamental studies because of its high catalytic activity for many chemical reactions, e.g. its ability to absorb hydrogen [41], On the other hand, due to hydrogen absorption, only brittle Pd deposits can be obtained in aqueous solutions. The advantage of performing electrodeposition of Pd in ionic liquids is that hydrogen evolution does not occur. Sun et al. demonstrated that Pd and some of its alloys, namely Pd-Ag [42], Pd-Au [43] and Pd-In [44], can be obtained from the basic l-ethyl-3-methylimidazolium chloride/tetrafluoroborate ionic liquid. Compact alloy deposits were obtained and the Pd content in the deposits increased with the increase in Pd mole fraction in the plating bath. 

CdTe, a II—VI compound semiconductor with a direct band gap of 1.44 eV at room temperature, is, from its physical properties, a promising photovoltaic material. The electrodeposition of CdTe in ionic liquid was published recently by Sun et al. [38]. They were able to show that the semiconductor can be electrodeposited at elevated temperature (above 120 °C) in the Lewis basic l-ethyl-3-methylimidazolium chloride/tetrafluoroborate ionic liquid containing CdCh and TeCU. CdTe films were obtained by the underpotential deposition (UPD) of Cd on the deposited Te. The deposit composition was independent of the deposition potential within the Cd UPD regime. The crystallinity of the deposits is improved by increasing the deposition temperature, which again demonstrates the high potential of the wide thermal windows of ionic liquids for compound electrodeposition. 

A relatively inexpensive route to halide-free tetrafluoroborate ionic liquids has been reported, shown in Scheme 2.3. In this one-pot reaction between glyoxal, methylamine, w-butylaminc, formaldehyde, and tetrafluoroboric acid a mixture of dialkylimidazolium tetrafluoroborate salts... 

There is only one example of a catalytic Pauson-Khand reaction in an ionic liquid1471 although the reaction has also been conducted in ionic liquids using stoichiometric amounts of Co2(CO)8/481 In the catalysed reaction 10 mol% of Co2(CO)8 was used in [C4Ciim][PF6] under 10 bar of CO. Under these conditions, diethylallyl malonates could be obtained in 90-99% yield within 90 minutes at 80°C, as shown in Scheme 9.14. However, with hetero-bridged enynes, as well as in the reaction between norbomene and phenylacetylene, only poor to moderate yields were achieved. A slight increase in activity was observed with the analogous tetrafluoroborate ionic liquid. 

The electrodeposition of several metals and alloys has been investigated in tetrafluoroborate ionic liquids. In contrast to the chloroaluminate ionic liquids, the tetrafluoroborate ionic liquids are considerably more stable against moisture and are expected to be applicable to practical use. Moreover the co-deposition of... 

Trombetta E, de Souza MO, de Souza RE et al (2009) Electrochemical behavior of aluminum in l-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid electrolytes for capacitor applications. J Appl Electrochem 39 2315-2321... 

Hsiu SI, Tai CC, Sun IW (2006) Electrodeposition of paUadium-indium from l-ethyl-3-methylimidazoUum chloride tetrafluoroborate ionic liquid. Electrochim Acta 51 2607-2612... 

Tai CC, Su FY, Sun IW (2005) Electrodeposition of palladium-silver in a Lewis basic 1-ethyl-3-methyUmidazolium chloiide-tetrafluoroborate ionic liquid. Electrochim Acta 50 5504-5509... 

Yang MH, Yang MC, Sun IW (2003) Electrodeposition of indium antimonide from the water-stable l-ethyl-3-methylimidazolium chloride/tetrafluoroborate ionic liquid. J Electrochem Soc 150 C544-C550... 

In none of the above cases has a reaction been performed whilst taking the EXAFS data. Hamill et al. [50] have investigated catalysis of the Heck reaction by palladium salts and complexes in room-temperature ionic liquids. On dissolution of palladium ethanoate in [BMIM]+ and N-butylpyridinium ([BP]+) hexafluorophos-phate and tetrafluoroborate ionic liquids, and triethyl-hexyl ammonium bis(trifluo-romethanesulfonyl)imide, a gradual change from ethanoate coordination to the formation of palladium metal was observed in the Pd K-edge EXAFS, as shown in Figure 4.1-13. 

Heck couplings of aryl halides with alkenes in room temperature ionic liquids have been reported [44]. Dialkylimidazolium and n-hexylpyridinium hexafluoro-phosphate and tetrafluoroborate ionic liquids were used as solvents, Pd(OAc)2 and PdCl2 as catalysts, and an amine as base. Addition of ligands such as triphe-nylphosphine, tri-o-tolylphosphine, and triphenylarsine usually had a negative affect on product yield. Addition of cosolvents such as DMF was not necessary. Palladium-catalyzed Heck reactions involving aryl bromides have been performed... 

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