Cyclic sulfur nitrogen compounds and phosphorus reagents: Part XII. Reactions of S<inf>4</inf>N<inf>4</inf> with (2†pyridylamino) phosphines [1]

Tetrasulfurtetranitride, S4N4 reacts with (2‐pyridylamino)‐diphenylphosphine in MeCN at room temperature to form the cyclotrithiazene (NC5H4NH)‐Ph2PNS3N3 (1) in good yield. By contrast, the cyclophosphathiazenes Ph2PS2N3 (2) and 1,5(Ph2P)2S2N4 (3) are isolated from the same reaction mixture under reflux conditions. In solution, compound 1 is found to be transformed into 2. The reaction of S4N4 with (2‐pyridylamino)phenyl(dicyclohexylamino)phosphine in MeCN at room temperature affords Ph(DCA)PS2N3 (4) (DCA = dicylohexylamino) as the only reaction product. This on treatment with norbornadiene produces the addition product Ph(DCA)PS2N3·C7H8 ( 5 ). The structure of 4 has been established by X‐ray diffraction. Its PSN ring adopts a skew boat conformation with SN bond lengths varying from 1.574(4) to 1.606(4) Å. The mean value of the endocyclic PN bonds amounts to 1.618(3) Å. Copyright © 1994 VCH Publishers, Inc.