Chalcogen‐Expanded Unsaturated Silicon Clusters: Thia‐, Selena‐, and Tellurasiliconoids

Reactions of silylenes with heavier chalcogens (E) typically result in Si=E double bonds or their π‐addition products. In contrast, the oxidation of a silylene‐functionalized unsaturated silicon cluster (siliconoid) with Group 16 elements selectively yields cluster expanded siliconoids Si(7)E (E=S, Se, Te) fully preserving the unsaturated nature of the cluster scaffold as evident from the NMR signatures of the products. Mechanistic considerations by DFT calculations suggest the intermediacy of a Si(6) siliconoid with exohedral Si=E functionality. The reaction thus may serve as model system for the oxidation of surface‐bonded silylenes at Si(100) by chalcogens and their diffusion into the silicon bulk.