Synthese und Eigenschaften von 3,6-Diorgano-3,6-dithio-1,2,4,5,3,6-tetrathiadiphosphorinanen; eine neue Möglichkeit zur Knüpfung von S—S-Bindungen / Synthesis and Properties of 3,6-D iorgano-3,6-dithio-1,2,4,5,3,6-tetrathiadiphosphorinanes; a New Possibility of Forming S—S Bonds

The six-membered sulfur-phosphorus heterocycles 3,6-diorgano-3,6-dithio-1,2,4,5,3,6-tetrathiadiphosphorinanes (RP(S)S2)2 (R = Me 1a and R = t-Bu 1b ) are formed in high yields from the silyl esters of the corresponding trithiophosphonic acids RP(S)(SSiMe3)2 and dimethylsulfoxide. They are fairly stable in the crystalline state. In solution sulfur elimination occurs, which in the case of l a leads to the formation of 3,5-dimethyl-3,5-dithio-1,2,4,3,5-trithiadiphospholane, MeP(S)S2PMe(S)S (4). Likewise lb decomposes to give the corresponding dithiophosphonic acid anhydride (t-BuP(S)S)2. According to NMR spectroscopic conformational analysis, 1a exists in four isomeric forms: two chair and two twist-boat conformations, which differ in the orientation (cis or trans) of the Me groups. The isomeric distribution indicates that the Me groups prefer the axial positions. As a consequence of steric bulk, 1b is only present in the twist-boat conformation with trans orientation of the t-Bu substituents.