Bismabenzene

Bismabenzene is the parent representative of a group of organobismuth compounds that are related to benzene with a carbon atom replaced by a bismuth atom. Bismabenzene itself has been synthesised but not isolated because it is too reactive, tending to instead dimerize in a Diels-Alder addition.
File:Bond lengths of group 15 heterobenzenes and benzene.svg|center|thumb|620px|Bond lengths and angles of benzene, pyridine, phosphorine, arsabenzene, stibabenzene, and bismabenzene
An unstable derivative with 4-alkyl substituents was reported in 1982. A stable derivative, with two arene [substitution pattern|ortho] trisilyl substituents, was synthesized from aluminacyclohexadiene, bismuth trichloride, and DBU in 2016.