Acyl-Phosphide Anions via an Intermediate with Carbene Character: Reactions of K[PtBu2 ] and CO.

The analogy of the reactivity of group 1 phosphides to that of FLPs is further demonstrated by reactions with CO, affording a new synthetic route to acyl-phosphide anions. The reaction of [K(18-crown-6)][PtBu2 ] (1) with CO affords [(18-crown-6)K⋅THF2 ][Z-tBuP=C(tBu)O] (2⋅THF2 ) as the major product, and the minor product [K6 (18-crown-6)][(tBu2 PCO)2 ]3 (3). Species 2 reacts with either BPh3 or additional CO to give [K(18-crown-6)][(Ph3 B)tBuPC(tBu)O] (4) and [K(18-crown-6)][(OCtBu)2 P] (5), respectively. The acyl-phosphide anion 2 is thought to be formed by a photochemically induced radical process involving a transient species with triplet carbene character, prompting 1,2-tert-butyl group migration. A similar process is proposed for the subsequent reaction of 2 with CO to give 5.