(Phosphanyl)phosphaketenes as building blocks for novel phosphorus heterocycles.

Although BH simply coordinates the endocyclic P of (phospholidino)phosphaketene , the bulkier B(CF) gives rise to a zwitterionic diphosphirenium, which is a novel type of 2π-electron aromatic system as shown by the calculated NICS values. While the reaction of with Na[PCO(dioxane) ] is unselective, the same reaction with the sterically bulky (phospholidino)phosphaketene [Ar** = 2,6-bis[di(4--butylphenyl)methyl]-4-methylphenyl selectively affords a sodium bridged dimer containing a hitherto unknown λ,λ,λ-triphosphete core. The latter formally results from "P" addition to a 1,3-P/C-dipole. Similarly, adamantyl isonitrile adds to giving a 4-membered phosphacycle. In contrast to , the phosphaketene derived from the electrophilic diazaphospholidine-4,5-dione is unstable and reacts with a second molecule of Na[PCO(dioxane) ] to afford a 1,3,4-oxadiphospholonide derivative.