A Crystalline Ylide‐Stabilized Stibenium Cation

We report the isolation of the first stibenium cation stabilized by two thiophosphinoyl‐tethered ylide substituents. The cation is directly accessible via salt metathesis between the metalated ylide and antimony trichloride. Despite the typically strong electron‐donating character of ylide substituents, crystal structure analysis in combination with detailed computational studies reveals the presence of CSb single bonds, with the lone pairs remaining localized at the ylidic carbon centers. Instead, stabilization of the stibenium cation arises from the thiophosphinoyl groups, which provide both steric protection and additional SSb interactions. In contrast, a sulfonyl‐functionalized ylide fails to sufficiently stabilize an analogous stibenium cation, highlighting the decisive influence of ylide substituent design on the stabilization of highly reactive main‐group cations.