π-Aromatic B16H6: A Neutral Boron Hydride Analogue of Naphthalene

Systematic ab inito calculations are carried out in this work to investigate the geometrical and electronic structures of B16H6 neutral and its anion B16H6 (-). The quasi-planar C-2v B16H6((1)A(1)) with 10 delocalized pi-electrons proves to be the neutral boron hydride analogue of naphthalene (D-2h C10H8). This pi-aromatic neutral may be obtained from the experimentally known pi-antiaromatic C-2h B-16 (Sergeeva et al., J. Am. Chem. Soc. 130:7244, 2008) upon hydrogenation at the six corner positions and is expected to be undistinguishable from a perfect planar D-2h B16H6 in experiments. Detailed adaptive natural density partitioning (AdNDP) analyses clearly reveal the bonding pattern of B16H6 and the calculated nucleus independent chemical shifts (NICS) strongly support its global pi-aromaticity. C-2v B16H6 (-)(B-2(2)) anion with one extra electron appears to have a similar quasi-planar structure with even a less severe out-of-plane distortion. Ultraviolet (UV) absorption spectrum of B16H6 and photoelectron spectroscopy (PES) spectrum of B16H6 (-) are simulated to facilitate their spectroscopic characterizations.