Phosphanyl Cyanophosphide Salts: Versatile PCN Building Blocks.

The facile preparation of alkali salts of phosphanyl cyanophosphides [NHP-PCN]- (NHP=N-heterocyclic phosphenium) is reported. Their formation is achieved by isoelectronic replacement of O for [N]- in the phosphaketenes NHP-PCO using alkaline hexamethyldisilazide M[N(SiMe3 )2 ] (M=Na, K) as reagent. The new anionic entities are versatile PCN building blocks which allow the formation of a diversity of new cyanophosphine derivates including the first example of a PCNB hetero-cumulene and a PCN-ligated transition metal complex.