Convenient synthesis of perfluoroalkyltrifluoroborates

Abstract

Perfluoroalkyltrimethoxyborates were converted into the corresponding perfluoroalkyltrifluoroborates in high yield by the action of potassium bifluoride in acidic media, i.e. in hydrochloric acid (37%), glacial acetic acid, and trifluoroacetic acid as well as in acidic ionic liquids. These low-cost methods avoid the use of toxic and corrosive hydrofluoric acid or anhydrous HF (aHF). Potassium and sodium perfluoroalkyltrifluoroborates are highly valuable starting materials for the preparation of low viscosity ionic liquids and organic salts with [RFBF3]− anions, in general, and for the synthesis of further perfluoroalkylborate anions, for example perfluoroalkylcyanofluoroborates [RFBF3-n(CN)n]− (n = 1–3). Furthermore, complex metal cations are accessible with the weakly coordinating [RFBF3]− counterions, as exemplified by the synthesis of [Cu(bpy)3][C2F5BF3] (bpy = 2,2′-bipyridine).