A Stable Aromatic Tetrasilacyclobutadiene Dication

J Am Chem Soc. 2019 Sep 25;141(38):14987-14990. doi: 10.1021/jacs.9b08018. Epub 2019 Sep 17.

Abstract

The isolation and characterization of the first silicon analogue of the aromatic cyclobutadiene dication is reported. The aromatic 2π-electron tetrasilacyclobutadiene dication in [(LPhSi)4](BPh4)2 (LPh = PhC(NtBu)2) has been obtained in a simple and straightforward synthesis, from [LPhSiCl], [LPhSiSiLPh] and NaBPh4, and fully characterized. The molecular structure reveals a four-membered Si4-dication in an almost perfect square-planar geometry. Theoretical calculations support the interpretation of the title compound as a classical 2π-aromatic species with a singlet ground state.