Trapping Rare and Elusive Phosphinidene Chalcogenides

Four‐membered rings with a P2Ch2 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 P2Ch2 rings can liberate phosphinidene chalcogenides. Four‐membered rings with a P2Ch2 core (Ch=S, Se) have been synthesized by the cyclocondensation of Ar*PCl2 and Ch(TMS)2, where phosphorus remains in the +3 oxidation state (Ar*=2,6‐Mes2C6H3, Mes=2,4,6‐(CH3)3C6H2). The utility of these rings as a source of monomeric phosphinidene chalcogenides was probed via the addition of an N‐heterocyclic carbene (NHC) and 2,3‐dimethylbutadiene.