2-[(Di­methyl­phenyl­phosphanyl­idene)aza­nium­yl]-5-methyl­benzene­sulfonate benzene monosolvate

The title compound, C₁₅H₁₈NO₃PS·C₆H₆, is a rare example of a crystallographically characterized exocyclic phosphiniminium-arene­sulfonate zwitterion, which crystallises as its benzene solvate. The crystal structure shows that the N atom is protonated and that the iminium H atom forms both intra- and inter­molecular hydrogen bonds to the single-bonded sulfonate O atom in an R₂²(4) graph-set motif. The dihedral angle between the aromatic rings in the main molecule is 89.49 (8)°.