Heavy analogues of the 6π-electron anionic ring systems: Cyclopentadienide ion and cyclobutadiene dianion

The heavy analogues of the anionic 6π-electron systems, lithium 1,2-disila-3-germacyclopentadienide 2− · [Li+(thf)], 1,2-disila-3,4-digerma- and 1,2,3,4-tetrasilacyclobutadiene dianions 72− · 2[K+(thf)2] and 82− · 2[K+(thf)2], were synthesized by the reduction of the neutral precursors 1, 3 and 4, respectively. 2− · [Li+(thf)], the heavy analogue of the cyclopentadienide ion, is an aromatic compound, whereas 72− · 2[K+(thf)2] and 82− · 2[K+(thf)2], the heavy analogues of the cyclobutadiene dianion, are both non-aromatic.