Structural similarity between boron oxide B_n(BO)_n^2– and boron hydride B_nH_n^2– dianions (<i style="mso-bidi-font-style:normal">n</i> = 4–12)

Abstract

The boron oxide dianions B_n(BO)_n^2– (<i style="mso-bidi-font-style: normal">n</i> = 4–12) are studied using DFT (B3LYP) method. Geometries of the global minima of B_n(BO)_n^2– with <i style="mso-bidi-font-style:normal">n</i> = 4–12 are found to be analogous to those of boron hydrides. All boron oxides considered exhibit large HOMO-LUMO gaps and high vertical detachment energies. Similar to B_nH_n^2–, the enhanced thermodynamic stabilities are established for B_n(BO)_n^2– at <i style="mso-bidi-font-style:normal">n</i> = 6, 10 and 12. Due to the strength of BO bonds, oxidation of boron clusters thus consistently leads to formation of exohedral boronyls that in turns behave as substituents replacing the hydrogen atoms. This structural similarity allows the shape of boron oxides to be predicted from boron hydrides. Nevertheless, the BO bonds are expected to be the preferred reaction sites of boron oxides.