Centrohexaindane, a Unique Polyaromatic Hydrocarbon Bearing the Rare C (C ) Core: Inelastic Neutron Scattering, Infrared and Raman Spectroscopy.

The structure and vibrational spectroscopy of centrohexaindane, 1, was investigated. This unusual molecule has a quaternary carbon atom that is coordinated to four further such quaternary carbon atoms as its core, each pair of which is bonded to an ortho-phenylene unit. Previous NMR studies have shown that the molecule has tetrahedral (T ) symmetry in solution. The infrared and Raman spectra of chloroform and deuterochloroform solutions of 1 are completely in agreement with this conclusion, as the only modes that are visible are those allowed for T symmetry. This is not the case in the solid state: X-ray powder diffraction indicates that the unit cell is triclinic or monoclinic with a volume in excess of 4000 Å . The vibrational spectroscopy is consistent with C site symmetry and the presence of at least two molecules in the primitive cell. It is likely that the space group is centrosymmetric.