Wikipedia
Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate is an anion with chemical formula [{3,5-(CF)CH}B], which is commonly abbreviated as [BAr] as the boron atom (B) is surrounded by four fluorinated aryl (Ar) groups. It is sometimes referred to as Kobayashi's anion in honour of Hiroshi Kobayashi who led the team that first synthesised it, but more commonly it is affectionately nicknamed "BARF." BARF has a tetrahedral geometry around the central boron atom but each of the four surrounding aryl groups is aromatic and planar. The motivation for its preparation was the search for an anion which coordinates more weakly than the then-available ions hexafluorophosphate, tetrafluoroborate, or perchlorate. Salts of this anion are known as solids and in both aqueous and non-aqueous solutions. BARF can be used in catalytic systems where the active site requires an anion which will not coordinate to the metal centre and interfere with the catalytic cycle, such as in the preparation of polyketones.