Rearrangements in icosahedral boranes and carboranes revisited

The structure, stability, and intermolecular rearrangements between ortho-, meta-, and para-C2B10H12 and B12H122- were investigated using the hybrid density functional B3LYP/6-31G(d) for vibrational frequencies, as well as B3LYP/6-311+ G(2d, p) for single-point electronic energies. The general trends in free energies of rearrangement between ortho- C2B10H12 to meta- C2B10H12 and meta- C2B10H12 to para-C2B10H12 presented here are consistent with experimental reaction temperatures. In addition, the majority of the rearrangements can be viewed in terms of concerted diamond - square - diamond steps and triangular face rotations.