Stable Ketenyl Anions via Ligand Exchange at an Anionic Carbon as Powerful Synthons**

Abstract

AbstractUnder an atmosphere of carbon monoxide (CO), a (phosphino)diazomethyl anion salt [[P]‐CN2][K(18‐C‐6)(THF)] (1) ([P]=[(CH2)(NDipp)]2P; 18‐C‐6=18‐crown‐6; Dipp=2,6‐diisopropylphenyl) undergoes a facile N2/CO exchange reaction giving the (phosphino)ketenyl anion salt [[P]‐CCO][K(18‐C‐6)] (2). Oxidation of 2 with elemental Se affords the (selenophosphoryl)ketenyl anion salt [P](Se)‐CCO][K(18‐C‐6)] (3). These ketenyl anions feature a strongly bent geometry at the P‐bound carbon and this carbon atom is highly nucleophilic. The electronic structure of the ketenyl anion [[P]‐CCO]− of 2 is examined by theoretical studies. Reactivity investigations demonstrate 2 as a versatile synthon for derivatives of ketene, enolate, acrylate and acrylimidate moieties.