Frontispiece: Syntheses and Properties of Tin‐Containing Conjugated Heterocycles

Stannoles are tin analogues of cyclopentadienes that exhibit a special form of conjugation involving σ* and π* orbitals (equivalent to LUMO and LUMO+1). This reduces the energy gap to the HOMO compared to cyclopentadienes, which makes stannoles interesting and unusual materials. The synthesis of such stannoles and polymeric stannoles is still a challenge in many cases and further developments are necessary. For a full discussion see the Concept article by A. Staubitz and colleagues on page 5680 ff.