Reaction of benzylidenetriphenylphosphorane with 1,4-dichloro-3а,6а-diaza-1,4-diphosphapentalene

The transylidation between 1,4-dichloro-3a,6a-diaza-1,4-diphosphapentalene and benzylidenetriphenylphosphorane (Ph₃P=CHPh) results in either mono- or disubstitution of chlorine atoms by the Ph₃P=C(Ph) group depending on the reactant molar ratio. In the crystal, the monosubstituted product has the planar diazadiphosphapentalene ring and the P—Cl ionic bond. The ³¹P NMR spectra of this compound exhibit a strong solvent-dependent behavior, which indicates that it exists both in the ionic form (in CH₂Cl₂, MeCN) and the molecular form (in THF). In the disubstituted product, the diazadiphosphapentalene skeleton is non-planar and is bent along the N—N bond.