Masked Silylenes: Controlled Generation and Reactivity Under Thermal and Equilibrium Conditions

Silylenes (divalent silicon species) are highly reactive intermediates that are often difficult to handle directly. Although steric protection and electronic stabilization have enabled the isolation of persistent silylenes, such stabilization tends to restrict their intrinsic reactivity. Masked silylenes offer an alternative strategy in which the reactive silicon(II) center is temporarily embedded in a precursor framework or coordination environment. As a result, the precursor can be handled or even isolated, and silylene reactivity is accessed in situ by thermal activation. This review focuses on masked silylene chemistry governed by thermolysis and reversible equilibria and summarizes how precursor structure controls the generation of silylenes and their subsequent reactivity. Representative precursor classes include SiC 2 ‐derived strained frameworks, SiC 6 arene adducts such as 7‐silanorbornadienes and silepins, SiE double‐bond systems (E = Si, N), as well as Lewis‐base adducts and σ‐bond complexes. Typical reactivity patterns and applications, including trapping reactions, small‐molecule activation, and organosilicon synthesis, are highlighted.