Jahn–Teller Effect in the B12F12 Radical Anion and Energetic Preference of an Octahedral B6(BF2)6 Cluster Structure over an Icosahedral Structure for the Elusive Neutral B12F12

The B12F12 – radical anion was generated by oxidation of [CoCp2 +]2B12F12 2– with AsF5 in SO2. In the crystal structure of [CoCp2 +]­B12F12 –, the anion displays a lowered symmetry (D 2h ) instead of an Ih -symmetric dianion as a result of Jahn–Teller distortion. Moreover, shortening of the B–F bonds and subtle changes of the B–B bonds are observed. DFT calculations show that, for the unknown neutral B12F12, unprecedented structural isomers [e.g., octahedral B6(BF2)6] are energetically favored instead of an icosahedral structure. The structures and energetics are compared with those of the analogous chlorine compounds.