Anionic indabenzene: synthesis and characterization.

An anionic indabenzene was synthesized via the transmetallation of an aluminacyclohexadiene with bulky silyl substituents, and fully characterized using multinuclear NMR spectroscopy and X-ray crystallography. The observed structural features are consistent with the formal criteria of aromaticity. Additionally, the results of DFT calculations suggested contributions from an ambiphilic resonance structure, similar to the corresponding aluminum and gallium derivatives.