Eight different conformations have been determined by ab initio calculations at the MP2/6-31G(d,p) level, although two of these are so close in terms of structure and energy that it is unlikely that they experimentally exist as separate species. Relative energies have been obtained at the CCSD(T)/6-31G(d,p), MP2/6-311 + +G(2d,2p) and MP2/cc-pVQZ levels. The experimental results are consistent with the observation of the three lowest-energy isomers, although the experimental energy difference for the two lowest species appears to be in error.
