Electrochemical, plasma and synthetic studies of dithiadiazolium and related compounds

Abstract

The crystal structure of [PhCNSSN] AsF(_6) and (MeCSSN)(_2) have been determined and a variety of new 1,2 and 1,3 dithiadiazolium derivatives synthesised including [CH(_3)CH(_2)CH(_2) CNSSN]C1 and[(CH(_3)(_3)CCNSSN]C1. [PhCN(_2)S(_2)] AsF(_6) has a longer S-S bond compared to [PhCN(_2)S(_2)]C1 and has provided an insight into the molecular bonding in the three centre interactions in the latter. The crystalline methyldithiadiazole contains planar CNSSN rings. Within the dimer unit parallel monomer rings are linked via one weak S...S bond. Enthalpies of fusion for a number of dithiadiazole derivatives were measured and found to be similar but significantly greater than for organic molecules of similar molecular weight. This together with the reduction of [CH(_3)CH(_2)CH(_2)CN(_2)S(_2)]CI and [(CH(_3))(_3)CCN(_2)S(_2)]C1 which gave new paramagnetic liquids has led to a more detailed understanding of the bonding and structure in these ring systems. Dimeric aryldithiadiazoles (RCNSSN)(_2) (R = Ph or p – C1Ph) were treated with atomic nitrogen, generated in a cool DC plasma, to form the corresponding dithiatriazine dimers by nitrogen insertion into the S-S bond; Alkyl derivatives (R = Me, propyl, bu(^t)) gave polymeric products. Dithiadiazolium salts [RCNSSN](^+)X(^-) (R = Ph, p-ClPh), X = Br, I, CN or S(_3)N(_3)) also reacted with nitrogen plasma to give high yields of the respective dithiatriazine. Structural criteria for these reactions are discussed. The electrochemistry of (RCNSSN)(_2), (RCNSSN)(_2), [RCNSSN]X (X=C1- or AsF(_6)(^-) and [RCNSNS] AsF(_6) (R= Ph,p-C1Ph,p-CH3Ph,p-CNPh,anthracene,Me, propyl,bu(^t),C1(_3)C, CF(_3)) were studied by cyclic voltammetry.A new S(_2)N(^+ )salt, S(_2)NCF(_3)SO(_3), was synthesised from the reaction of AgCF(_3)SO(_3) with (NSC1)(_3) and sulphur in liquid SO(_2) and its usefulness as a reagent compared to S(_2)NAsF(_6) and S(_2)NSbC1(_6). The crystal structure of S(_3)N(_2)CF(_3)SO(_3) was determined, crystals of which were isolated from the same reaction mixture and an equilibrium between S(_2)N(^+),SN(^+) and S(_3)N(_2)(^+)(^.) postulated.