Creation of exotic π-electron systems by introduction of heavy elements and expansion of the concept of aromaticity

Abstract

We succeeded in the synthesis of dilithio-stannoles and a -plumbole, which possess aromatic character, as evidenced by structural analysis and quantum-chemical calculations, and accordingly the concept of aromaticity can now be expanded to tin- and lead-containing π-conjugated systems. Reactivity of dilithio-stannoles and a -plumbole toward alkyl-, aryl-, and metal-halides was investigated. Stepwise oxidation of a dilithiostannole using oxygen gas yielded a 1, 2-dilithiobistannole and a 1, 3-dilithioterstannole. The combination of the aromatic dianionic ligands and transition metals produced unique electronic structures that could not be created by the use of cyclopentadienyl and its related carbon-only ligands. These new findings would inspire a new chemical bond theory, materials science, and catalytic chemistry. The serendipitous formation of a pentaorganostannate bearing five carbon substituents and a dibenzopentalenide is also described.