Stabilization of an All-Metal Antiaromatic Molecule (Al₄Li₄) Using BH and C as Caps

Abstract

It has been reported by Pati et al. (J. Am. Chem. Soc. 2005, 127, 3496) that coordination with a transition metal can stabilize the "antiaromatic", all-metal compound Al₄Li₄. Here, we report that it can also be stabilized by capping with a main group element like C and its isoelectronic species BH. Our calculations of binding energy, nuclear independent chemical shift, energy decomposition analysis, and molecular orbital analysis support the capping-induced stability, reduction of bond length alternation, and increase of aromaticity of these BH/C-capped Al₄Li₄ systems. The interaction between p_x and p_y orbitals of BH/C and the HOMO and LUMO of Al₄Li₄ is responsible for the stabilization. Our calculations suggest that capping can introduce fluxionality at room temperature.