Aromatic benzannulated germole dianions. The dilithio and disodio salts ofa germaindenyl dianion

Conversion of the neutral 1,1-dichloro-DPGI (1) (DPGI = 2,3-diphenyl-1-germ aindene) to the lithium dianion (2a) or sodium dianion (2b) leads to the hi ghly unusual phenomenon of aromatization of the GeC4 portion of 1-germainde ne at the expense of the aromatic annulated Ca ring. Treatment of 2a with t rimethylchlorosilane gave the 1,1-bis(trimethylsilyl)-DPGI derivative (3) i n high yield. The structure of 2a was determined by X-ray crystallography a nd found to possess two eta(5)-coordinated lithium ions. The five-membered ring of the germaindenyl system undergoes significant carbon-carbon bond eq ualization upon formation of the dianion, while the remaining four carbon a toms become diene-like, exhibiting two short bonds separated by a long bond .