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

Abstract 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 7 2 −  ·  2[K + (thf) 2 ] and 8 2 −  ·  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 7 2 −  ·  2[K + (thf) 2 ] and 8 2 −  ·  2[K + (thf) 2 ] , the heavy analogues of the cyclobutadiene dianion, are both non-aromatic.