Partially Naked Fluoride in Solvate Ionic Liquids.

Truly naked fluoride exists only in the gas phase. Fluoride can be stabilized by a complexing agent and an organic cation, resulting in anhydrous or dehydrated fluoride which is "partially naked." This partially naked fluoride enables fluorination reactions at much lower temperatures than hydrated fluorides. Here we show a simple method for preparing fluoride-based solvate ionic liquids (SILs) by mixing 1-alkyl-3-methylimidazolium (1-ethyl-3-methylimidazolium or 1-butyl-3-methylimidazolium) bromide, silver fluoride (AgF), and EG (1:1:1 in molar ratio) in dry methanol. Removal of the methanol produced anhydrous SILs, [C2C1im]F·EG and [C4C1im]F·EG. This is the first SIL reported that comprises fluoride. 1H NMR and infrared spectroscopy reveal fluoride hydrogen bonds with EG OH groups and cation aromatic H atoms but not cation tail group protons. Fluorination reactions on benzyl bromide show that [C2C1im]F·EG has high reactivity with reasonable yield under mild conditions, confirming the fluoride ion is partially naked.