Lithium bis trifluoromethylsulfonyl imide

[Gun][PF 6 ]:
[Gun][PF 6 ] was synthesized by refluxing [Gun]Cl (20.0 g, 0.21 mol) (Sigma-Aldrich) and KPF 6 (38.5 g, 0.21 mol) (Sigma-Aldrich) in acetone (150 mL) for 1 week. The suspension was filtered and [Gun][PF 6 ] was obtained as a white solid by evaporation of the acetone under reduced pressure. The salt still contained some chloride impurities (AgNO 3 test), however due to its high melting point and low stability no further attempts were made to purify or characterize this compound.
[Gun][NTf 2 ]:
[Gun]Cl (20 g, 0.21 mol) and lithium bis(trifluoromethylsulfonyl)imide (60.3 g, 0.21 mol) (Io-li-tec) were each dissolved in the minimal amount of water. They were then combined resulting in a waxy white precipitate which was washed with a small amount of water. The precipitate was purified by dissolving it in acetone and standing at -20 °C to facilitate precipitation of LiCl before the solid was removed by filtration.
[Gun][NTf 2 ] (31 g, 0.09 mol, 43 % yield) was obtained as a white solid by evaporation of the acetone. Some chloride impurity was observed by the formation of a slightly milky solution when testing with an aqueous solution of AgNO 3 . However, the chloride content was found to be less than 0.1% w/w determined gravimetrically after the quantitative precipitation with an aqueous solution of AgNO 3 .
[

Materials. Choline chloride (99%) and tri-n-butyl phosphate (TBP, 98%) were purchased from Alfa Aesar (Karlsruhe, Germany) and betaine chloride (99%) from Acros Organics (Geel, Belgium). Lithium bis(trifluoromethylsulfonyl)imide (99%) was obtained from IoLiTec (Heilbronn, Germany). Trihexyl(tetradecyl)phosphonium chloride (>97%) (Cyphos® IL 101) and Cyanex ® 923 were purchased from Cytec Industrial