The Surprising Structures of B8F12 and B10F12

Unstable, reactive, and yellow: Compound B8F12, assumed for 30 years to have a diborane-like structure B2(BF2)6, has now been shown also to contain a short, central BB bond. Across the BB bond are two bridging BF2 groups, which are bent out of the plane by long-range, intramolecular F⋅⋅⋅B interactions. The B-(μ-BF2) bonds are long and, surprisingly, asymmetric, but calculations confirm that this structure is intrinsic to the molecule.