Bromine monofluoride
Bromine monofluoride is a quite unstable interhalogen compound with the chemical formula BrF. It can be produced through the reaction of bromine trifluoride (or bromine pentafluoride) and bromine. Due to its lability, the compound can be detected but not isolated:

BrF3 + Br2 → 3 BrF
BrF5 + 2 Br2 → 5 BrF
Br2(l) + F2(g) → 2 BrF(g)
It is usually generated in the presence of caesium fluoride. Bromine monofluoride decomposes at normal temperature through dismutation to bromine trifluoride, bromine pentafluoride, and free bromine. The molecular structure in the gas phase was determined by microwave spectroscopy; the bond length is re = 1.758981(50) Å. The bond length in a cocrystal with methylchloride is 1.822(2) Å; the lengthening relative to the free molecule is due to an interaction of the type F-Br···ClMe with a distance of 2.640(1) Å. See also 
 Bromine trifluoride, BrF3
 Bromine pentafluoride, BrF5

References 

Fluorides
Bromine(I) compounds
Interhalogen compounds
Diatomic molecules