N─H or O─H Bond Activation With a Bicyclic Si ₄ Ring Compound

The bicyclic silicon ring compound Si 4 {N(SiMe 3 )Mes} 4 (Mes = 2,4,6‐trimethylphenyl), a heavier analogue of cyclobutadiene, was reacted with ammonia, water, and selected alcohols. This resulted in E─H (E = N, O) bond activation, yielding saturated Si 4 rings with ─NH 2 /─H or ─OH/─H functionalities in the case of ammonia or water, respectively. With methanol, a mixture of a saturated Si 4 ring compound with ─OMe/─H functionalities and an eight‐vertex methoxy‐functionalized siliconoid cluster was obtained; an ethoxy‐functionalized analogue was obtained from the reaction with ethanol. In contrast, the reaction between Si 4 {N(SiMe 3 )Mes} 4 and phenol gave a simple 1,3‐addition product with only a trace of side products. The observed reactivity was rationalized with the help of mechanistic calculations performed using density functional theory.