Syntheses and Properties of Tin-Containing Conjugated Heterocycles

Heterocycles that contain tin atoms can be aromatic in a similar sense to well-known aromatic compounds such as benzene or thiophene, but such examples are rare. However, due to the low-lying sigma*-orbitals of the tin-substituent bond in stannoles, they are capable of sigma*-pi* conjugation in a way that is exclusive to heavier element containing heterocycles. This makes stannoles very interesting alternatives for purely organic heterocycles in material applications, in which optoelectronic properties are of interest. This Concept article will highlight the synthesis, reactivity and physical properties of stannoles and related fluorenostannoles. At first, a brief introduction to different types of tin-containing heterocycles is presented, followed by a discussion on different approaches to prepare stannoles, their reactivity and their physical properties. In addition, the first stannole-containing polymer will be reviewed.