New dense fluoroalkyl-substituted imidazolium ionic liquids

New mono and polyfluoroalkyl-substituted ionic liquids have been synthesized and characterized. The neat reaction of 1-methylimidazole (1a) with 1,1,1-trifluoro-3-iodopropane (2a) at 80°C formed the quaternary salt, 1-methyl-3-trifluoropropylimidazolium iodide (3), in 90% yield. Similarly, sodium imidazole (1b) gave good yields of the quaternary salts, 1,3-bis(trifluoropropyl)imidazolium iodide (3b) with an excess of 2a, and 1,3-bis(monofluoropropyl)imidazolium bromide (3c) with an excess of 1-fluoro-3-bromopropane (2b). In water as solvent, metathesis reactions of 3 with KPF6, LiN(SO2CF3)2 and KSO3CF3, and of 3b and 3c with KPF6 and LiN(SO2CF3)2 led to 4a–c, 4d,e, and 4f,g, respectively, in good isolated yields. Some of the di(polyfluoroalkyl)imidazolium salts are liquids with densities in excess of 1.8 g/cm3.