Trapping Rare and Elusive Phosphinidene Chalcogenides

Abstract Four‐membered rings with a P 2 Ch 2 core (Ch=S, Se) and phosphorus in the +3 oxidation state have been synthesized. The utility of these rings as a source of monomeric phosphinidene chalcogenides was probed by the addition of an N‐heterocyclic carbene, resulting in a base‐stabilized phosphinidene sulfide. Similarly, persistence of the phosphinidene selenide in solution was shown through cycloaddition chemistry with 2,3‐dimethylbutadiene at elevated temperatures. The observed reactivity was explained by detailed computational work that established the conditions upon which the P 2 Ch 2 rings can liberate phosphinidene chalcogenides.