Bromine Pentafluoride BrF 5 , the Formation of [BrF 6 ] - Salts, and the Stereochemical (In)activity of the Bromine Lone Pairs.

BrF 5 can be prepared by treating BrF 3 with fluorine under UV light in the region of 300 to 400 nm at room temperature. It was analyzed by UV-Vis, NMR, IR and Raman spectroscopy. Its crystal structure was redetermined by X-ray diffraction, and its space group was corrected to Pnma. Quantum-chemical calculations were performed for the band assignment of the vibrational spectra. A monoclinic polymorph of BrF 5 was quantum chemically predicted and then observed as its low-temperature modification in space group P2 1 /c by single crystal X-ray diffraction. BrF 5 reacts with the alkali metal fluorides AF (A=K, Rb) to form alkali metal hexafluoridobromates(V), A[BrF 6 ] the crystal structures of which have been determined. Both compounds crystallize in the K[AsF 6 ] structure type (R 3 ‾ ${\bar 3}$ , no. 148, hR24). For the species [BrF 6 ] + , BrF 5 , [BrF 6 ] - , and [IF 6 ] - , the chemical bonds and lone pairs on the heavy atoms were investigated by means of intrinsic bond orbital analysis.