1-Butyl-3-methylimidazolium hexafluorophosphate, also known as BMIM-PF<sub>6</sub>, is a viscous, colourless, hydrophobic and non-water-soluble ionic liquid with a melting point of âÂÂ8 ðC. Together with 1-butyl-3-methylimidazolium tetrafluoroborate, BMIM-BF<sub>4</sub>, it is one of the most widely studied ionic liquids. It is known to very slowly decompose in the presence of water.
BMIM-PF<sub>6</sub> is commercially available. It may be obtained in two steps: BMIM-Cl is synthesized by alkylating 1-methylimidazole with 1-chlorobutane. A metathesis reaction with potassium hexafluorophosphate gives the desired compound; the tetrafluoroborate may be prepared by analogously using potassium tetrafluoroborate.
BMIM-PF<sub>6</sub> has been investigated in electrochemistry where it serves both as solvent and electrolyte, and in electrochemical CO<sub>2</sub> reduction.