posted on 2018-11-06, 00:00authored byZhengfei Chen, Yuto Tonouchi, Kazuhiko Matsumoto, Masayuki Saimura, Rob Atkin, Takashi Nagata, Masato Katahira, Rika Hagiwara
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.