Two novel products, (Ph3P=N)2S4N4 and (Ph3P=N)3S+S4N5−, have been isolated from the reaction of triphenylphosphine with S4N4; an X-ray structural determination of (Ph3P=N)2S4N4 shows it to consist of a 1,5-disubstituted S4N4 ring with the exocyclic substituents in an axial, equatorial configuration.