A Comparison of Ruthenium‐Catalysed Arene Hydrogenation Reactions in Water and 1‐Alkyl‐3‐methylimidazolium Tetrafluoroborate Ionic Liquids

Abstract

The hydrogenation of benzene and other arene substrates under biphasic conditions is evaluated using the catalyst precursor Ru(h 6 -C 10 H 14 )(pta)Cl 2 (pta 1,3,5-triaza-7-phosphaadamantane) immobilised in water and 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids. The effect that contamination of the 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids with chloride has on the hydrogenation reaction has also been examined. Of the immobilisation solvents tested the optimum solvent was found to be chloride-free 1-butyl-3-methylimidazolium tetrafluoroborate. Catalytic turnovers in this solvent are highest, and in general, turnovers for the hydrogenation reactions follow the trend: chloride-free 1-butyl-3-methylimidazolium tetrafluoroborate > water > chloridecontaminated 1-butyl-3-methylimidazolium tetrafluoroborate.

Heterogeneous dehalogenation of arylhalides in the presence of ionic liquids

“…Bromobenzene was dehalogenated up to 25% conversion in [emim]BF 4 and iodobenzene up to 41% in the same ionic liquid ( Table 2, entries [16][17][18][19][20][21][22][23][24][25][26]. Since the removal of the aromatic hydrocarbon products is extremely facile due to their non-polar character, as quantified previously for benzene in several ionic liquids, 27 we believe that the system is worth studying further as it represents a potentially important 'green' process.…”

Catalytic Hydrogenation using Ionic Liquids as Catalyst Phase

“…Dyson et al also showed that it is important to account for the chloride concentration in the ionic liquid [87]. These authors proved that chloride impurities, resulting from the synthesis of the ionic liquid, have a strong influence on hydrogenation activity.…”

“…Dyson et al [87,88] applied ruthenium clusters as a catalyst for the hydrogenation of benzene, toluene, cymene, ethylbenzene, and chlorobenzene. A direct comparison of the two biphasic systems, water/organic solvent and ionic liquid/ organic solvent, showed that the TOFs obtained in the ionic liquid and the aqueous media were similar [88].…”

Ionic Liquids within Microfluidic Devices

“…Some ionic liquids have been shown to be by far the best non-aqueous media for biocatalytic processes due to their positive influences on enzyme stability and activity, as well as on the enantioselectivity of the reactions catalyzed by them (Park & Kazlauskas, 2003). When the right ionic liquid is chosen for a given reaction, it can lead not only to enhanced selectivity, yield or reaction rate, but it also improves the result of the work-up, from product separation (extraction/distillation) to recycling of the system ionic liquid/(bio)catalysts (Dyson et al, 2003;Pârvulescu & Hardacre, 2007;van Rantwijk & Sheldon, 2007). Separation of products from ionic liquid and ionic liquid recovery can be accomplished by distillation of product (if the product is sufficiently volatile), extraction with supercritical CO 2, or simple phase separation (if the product is immiscible in the ionic liquid) (Cornils, 1999).…”