CHAPTER 12.3. Hypervalent Chalcogen Compounds

Abstract

The hypervalent chalcogen compounds are reviewed, classifying mainly by the coordination number at the chalcogen atoms, which is closely related to the structure of the compounds. They supply structurally interesting compounds and versatile reactivities. Inter‐ and intramolecular weak interactions are also discussed, which act as the factor to stabilize and/or determine the structures of the compounds. The chemistry is also reviewed briefly for chalcogen compounds that contain two or more chalcogen atoms in proximity in space. Relatively strong intramolecular chalcogen–chalcogen interactions are observed in such systems, which form new types of hypervalent chalcogen compounds. As an extension of the concept of hypervalent bonds/interactions in chalcogen compounds, the chemistry of extended hypervalent compounds is discussed; their applications in the biological, pharmaceutical, and material sciences are at an early stage.