Acyl‐Phosphide Anions from Reactions of K[PtBu2] and CO via an Intermediate with Carbene Character

The anology 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][E‐tBuP=C(tBu)O] 2•THF2 as the major product, with the minor product, [K6(18‐crown‐6)][(tBu2PCO)2]3 3. Species 2 reacts with BPh3 or additional CO to give [K(18‐crown‐6)][(Ph3B)tBuPC(tBu)O] 4 and [K(18‐crown‐6)][(OCtBu)2P] 5, respectively. The acyl‐phosphide anion 2 is thought to be formed via 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.

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