A Neutral Planar Four-Membered Si 2 B 2 2π-Aromatic Ring.

The synthesis of the first inorganic four-membered neutral 2π-aromatic compound 2 is reported. This unique ring has been synthesized from a simple and straightforward reaction of amidinato-silylene with dichlorophenylborane, followed by the reduction with KC 8 in THF. Compound 2 has been fully characterized by single-crystal X-ray diffraction (SC-XRD), NMR spectroscopy, and mass spectrometry. The computational calculations reveal that the Si 2 B 2 ring is a π-delocalized system resulting from the interaction of p π orbital of B and Si-N σ* orbitals having pseudo π symmetry. Compound 2 is the first known example of a neutral planar inorganic analogue of cyclobutenyl dication.