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

摘要

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 center dot THF2][Z-tBuP=C(tBu)O] (2 center dot THF2) as the major product, and the minor product [K-6(18-crown-6)][(tBu(2)PCO)(2)](3) (3). Species 2 reacts with either BPh3 or additional CO to give [K(18-crown-6)][(Ph3B)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.