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

A (phosphino)diazomethyl anion salt 1 ([[P]−CN2][K(18-C-6)(THF)]) ([P] = [(CH2)(NDipp)]2P; 18-C-6 = 18-crown-6) behaves as a (phosphino)carbyne anion-dinitrogen adduct ([P]−C−←:N2). Under an atmosphere of carbon monoxide (CO), 1 undergoes a facile N2/CO ligand exchange reaction giving (phosphino)ketenyl anion salt [[P]−CCO][K(18-C-6)] 2. Oxidation of 2 with elemental Se affords (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 2 is examined by theoretical studies. Reactivity investigations demonstrate 2 as a versatile synthon for derivatives of ketene, enolate, acrylate and acrylimidate moieties.