Heavier Analogues of Vinylidene: Recent Advances in Syntheses and Reactivities

Vinylidenes featuring heavier group 14 elements (>E = E:, E = Si, Ge, Sn, Pb) represent a unique class of compounds in which the two group 14 centers exist in distinct oxidation (+II and 0) and coordination states. Owing to the presence of a reactive group 14 element in a formal zero oxidation state, most of these vinylidenes are mainly stabilized using Lewis bases such as N-heterocyclic carbenes (NHC), silylenes (NHSi), etc. These stabilization strategies have enabled the isolation of a growing number of homo- and hetero-vinylidenes, garnering significant interest from the synthetic main group chemistry community. This review provides a comprehensive overview of the recent developments in the synthesis, structural characterization, and reactivity of heavier vinylidenes. The reactivity studies of these vinylidenes include cycloadditions, nucleophilic substitution, oxidative addition, group transfer reactions, etc.