The first structural characterisation of a phosphonium amide: Synthesis, isolation and molecular structure of (Ph₃PEt)⁺(NPh₂)^-

The first isolation of a phosphonium amide, (Ph₃PEt)⁺ (NPh₂)^-, obtained via the deprotonation of a secondary amine (diphenylamine) with a phosphorus ylide (triphenylphosphonium ethylide), is described. An X-ray crystal structure provides the first observation of an essentially ion-separated Ph₂N^- anion in the solid state, though weak association with Ph₃PEt⁺ cations takes place through C-H⋯N hydrogen bonding. Cryoscopic and NMR spectroscopic data suggest that this association is not maintained in benzene solution.