Perfectly planar boronyl boroxine D3h B6O 6: A boron oxide analog of boroxine and benzene

Abstract

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, 1A1′) cluster is identified as the global minimum of the system at density functional theory (B3LYP) and molecular orbital theory levels, which lies at least ∼20 kcal/mol lower in energy than alternative structures. It can be formulated as B3O3(BO)3 and features a boroxol B 3O3 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 π aromaticity in boronyl boroxine, rendering it a true analog to boroxine and borazine. Upon electron attachment, the slightly distorted C2v B 6O6- (2, 2A2) 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]2Cr (4, 1Ag). © 2013 AIP Publishing LLC.