[BrF] - a unique molecular tetrahedral interhalogen ion containing a μ-bridging fluorine atom surrounded by BrF molecules.

The reaction of [NMe][BrF] with an excess of BrF leads to the compound [NMe][BrF]·BrF. It features molecular [(μ-F)(BrF)] anions of tetrahedron-like shape containing central μ-bridging F atoms coordinated by four BrF molecules. It is the most BrF-rich fluoridobromate anion by mass. Quantum-chemical calculations showed that the μ-F-Br bonds within the anion are essentially ionic in nature. The compound is the first example where F atoms bridge μ-like neither to metal nor to hydrogen atoms. It was characterized by Raman spectroscopy and by single-crystal X-ray diffraction. The latter showed surprisingly that its crystal structure is related to the intermetallic half-Heusler compound and structure type MgAgAs.