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. (C) 1997 Elsevier Science Ltd.