The synthesis of salts with the [B(CF3)4]− anion has been the starting point for new developments in the field of trifluoromethylboron chemistry. In contrast to the previous syntheses of (CF3)nB derivatives (n=1–3), achieved exclusively by CF3 transfer, the synthesis of the [B(CF3)4]− anion was accomplished by fluorination of the [B(CN)4]− anion with ClF or ClF3 in anhydrous HF. Owing to its thermal and chemical stability, [B(CF3)4]− is an attractive weakly coordinating anion. However, in concentrated sulfuric acid one of the four CF3 groups is solvolyzed to a CO ligand to yield the neutral borane carbonyl (CF3)3BCO. It has been shown that the borane carbonyl compound is a versatile synthetic building block, and numerous reactions have been investigated. The addition of nucleophiles to the C atom of the CO ligand is favored, and examples for new derivatives are the anions [(CF3)3BCPnic]− (Pnic=N, P, As). Under certain conditions, ligand-exchange reactions are also observed, for example, the formation of (CF3)3BNCH. Finally, the borane carbonyl compound is a component of the conjugated Brønsted–Lewis superacid HF/(CF3)3BCO.