Dilithioplumbole: a lead-bearing aromatic cyclopentadienyl analog.

Although the concept of aromaticity has long played an important role in carbon chemistry, it has been unclear how applicable the stabilizing framework is to the heaviest elements. Here we report the synthesis of dilithiotetraphenylplumbole by reduction of hexaphenylplumbole. X-ray crystallography revealed a planar structure with no alternation of carbon-carbon bond lengths in the five-membered ring core. Nuclear magnetic resonance spectra and relativistic theoretical calculations show considerable aromatic character in the molecule, thus extending aromaticity to carbon's heaviest congener.