Unusual bridging fluorine discovered in one-of-a-kind interhalogen ion

For the first time, chemists have synthesised an interhalogen compound exhibiting a unique central fluorine atom coordinated by four BrF₅ groups. The one-of-a-kind interhalogen ion in [NMe₄][Br₄F₂₁]·BrF₅ represents the first example of a central tetracoordinated fluorine bridging to neither metal nor hydrogen atoms.