Addressing the Nature of Phosphinidene Sulfides via the Synthesis of P−S Heterocycles

The phosphorus–sulfur heterocycles 1,2‐thiaphosphetenes and phosphirene sulfides have been prepared, and represent the first structurally characterized derivatives for either class of compound. These strained P−S ring systems are formed by the reaction of a phosphinidene sulfide and alkyne. Using an internal alkyne, only the 3‐membered PV, phosphirene sulfide was produced, whereas a terminal alkyne yielded a mixture of phosphirene sulfide and 1,2‐thiaphosphetene (PIII). Detailed computational analysis revealed that for numerous derivatives of alkynes, the corresponding 4‐membered rings are always more stable than the 3‐membered isomers. The electronic nature of “free” phosphinidene sulfides (R−P=S) is discussed based on computational results. PSycloadditions: Structural isomers, 1,2‐thiaphosphetene and phosphirene sulfide, have been synthesized and structurally characterized for the first time. The synthesis of these rings proceeds via the [1+2] or [2+2] cycloaddition of “free” phosphinidene sulfide and alkynes. Computational analysis reveals the stability, and hypothesized mechanism, for both isomers.