[(μ3‐F)(BrF5)3]− – An Unprecedented Molecular Fluoridobromate(V) Anion in Cs[Br3F16]

Abstract

AbstractThe reaction of Cs[BrF6] with BrF5 gave the compound Cs[Br3F16] with the unprecedented propeller‐shaped, C3‐symmetric [(μ3‐F)(BrF5)3]− anion. All other currently known fluoridobromates(V) contain only octahedral [BrF6]− anions, which, unlike the related [IF6]− anions, never exhibited stereochemical activity of the lone pair on the Br atoms. Despite the same coordination number of six for the Br atom in the [BrF6]− and [(μ3‐F)(BrF5)3]− anions, the longer μ3‐F−Br bonds provide additional space, allowing the lone pairs on the Br atoms to become stereochemically active. Cs[Br3F16] was characterized by single‐crystal X‐ray diffraction, Raman spectroscopy, and quantum‐chemical calculations for both the solid‐state compound and the isolated anion at 0 K. Intrinsic bond orbital calculations show that the μ3‐F−Br bond is essentially ionic in nature and also underpin the stereochemical activity of the lone pairs of the Br(V) atoms.