Cyclic S-N compounds and phosphorus reagents - Part XVIII: Synthesis and X-ray structural characterization of phosphiniminocyclotrithiazenes with a primary amino substituent

First examples of phosphiniminocyclotrithiazenes containing a primary amino group, (Ph)(R)((PrNH)-Pr-i)PN-S3N3 [R=(i) Ph, I and (ii) DCA (dicyclohexyl amino), II] have been isolated from room temperature reactions of S4N4 with the corresponding phosphine in acetonitrile. Single crystal X-ray structur e of compounds I and II reveal very similar endocyclic structural features, but for the deviation of tricoordinate sulphur [S(1)] from the mean plane of the ring. The primary amino group [(CH3)(2)CHNH] binds equally strongly in I and II, but the N-H bonds show differences in both bond length and ori entation with respect to the adjacent P-N bond. Heterocycles I and II show different sensitivities for ring conversion to cyclophosphathiazene.