Perfectly planar boronyl boroxine D3h B6O6: A boron oxide analog of boroxine and benzene

Inorganic benzene-like compounds such as boroxine and borazine are of interest in chemistry. Here we report on theoretical prediction of a new member of the inorganic benzene family: boronyl boroxine. This perfectly planar D-3h B6O6 (1, (1)A(1)') cluster is identified as the global minimum of the system at density functional theory (B3LYP) and molecular orbital theory levels, which lies at least similar to 20 kcal/mol lower in energy than alternative structures. It can be formulated as B3O3(BO)(3) and features a boroxol B3O3 ring as the core with three boronyl (BO) groups attached terminally, closely resembling boroxine and obtainable from the latter via isovalent BO/H substitution. Detailed bonding analyses reveal weak pi aromaticity in boronyl boroxine, rendering it a true analog to boroxine and borazine. Upon electron attachment, the slightly distorted C-2v B6O6- (2, (2)A(2)) anion is also perfectly planar, and its electronic properties are calculated. A huge energy gap (4.83 eV) is predicted for B6O6- (2) at B3LYP level, which is characteristic of a stable closed-shell neutral cluster. Similar to benzene, boronyl boroxine is also predicted to be an effective inorganic ligand to form sandwich-type complexes, such as D-3d [B3O3(BO)(3)](2)Cr (4, (1)A(g)). (C) 2013 AIP Publishing LLC.