Alkylimidazolium Fluorohydrogenates Room Temperature Molten Salts

Reaction of some N -alkylimidazolium chloride with anhydrous hydrogen fluoride (HF) gives involatile room temperature molten salt, RR'ImF · 2.3HF where RR'Im = 1,3-dimethylimidazolium (DMIm), 1-ethyl-3-methylimidazolium (EMIm), 1-methyl-3-propylimidazolium (PrMIm), 1-butyl-3-methylimidazolium (BMIm), 1-methyl-3-pentyl imidazolium (PeMIm), 1-hexyl-3-methylimidazolium (HMIm). Vacuum stable salts at room temperature exhibit the same composition regardless the type of the cation. High specific conductivities, 110 and 100 mScm −1 , are observed at 298 K for DMImF · 2.3HF and EMImF · 2.3HF, respectively. Substitution of the proton or the longer alkyl side chains for the ethyl group of the imidazolium cation decreases the conductivity. These salts are stable in air and do not etch a Pyrex glass container at ambient conditions. Electrochemical windows of these salts range around 3V. Elongation of the alkyl side chain on the cation tends to extend the cathode limit. These salts act as good Lewis bases against binary fluorides of some main group elements and transition metals to give ionic salts without involatile byproducts.