Cyclic S-N compounds and phosphorus reagents-XVH. Synthesis and X-ray structural characterization of (Ph)(DCA)(Me<inf>2</inf>N)P = N-S<inf>3</inf>N<inf>3</inf> heterocycle

The phosphiniminocyclotrithiazene, (Ph)(DCA)(Me2N)PN-S3N3 (II) [DCA = dicyclohexylamino] was obtained in ≈ 70% yield from room temperature reaction of S4N4 with the corresponding phosphine, (Ph)(DCA)(Me2N)P (I). Single crystal X-ray structure determination of (II) reveals slightly different P-N bond lengths around phosphorus [P-N(4): 1-607; P-N(5): 1-645 and P-N(6): 1-638 Å] and almost planar configuration around both N(5) and N(6). The Incoordinate sulphur [S(l)] substantially deviates (0-663 Å) from the mean plane of the heterocycle. The structural parameters of (II) are compared with the recently reported diethylamino and di-n-butylamino analogues. (II) affords (Ph)(DCA)(Me2N)P = N-S3N (IV) in ≈ 60% yield on thermolysis in solution.