Bis- and Tris-(1,2,3,4-Dithiadiazolium) salts and related radicals

Abstract

Using the cycloaddition of [SNS][AsF(_6)] to nitriles a variety of 5-substituted-1,3,2,4- dithiadiazolium salts (salts containing the -CNSNS cationic ring) were prepared : mono- (1,3,2,4-dithiadiazolium) salts from mononitriles, bis-(l,3,2,4-dithiadiazolium) salts from dinitriles and l,3,5-tris-(l,3,2,4-dithiadiazohum) salts from 1,3,5-tricyanobenzene. salts of these dithiadiazolium cations with other anions were prepared by simple anion metathesis reactions. Bis- and tris-(l,3,2,4-dithiadiazolium) salts were reduced to give stable bis- and tris- (1,3,2,4-dithiadiazolyl) radicals which were studied by electron spin resonance spectroscopy (ESR). These multiradicals were formed as dark, sparingly soluble powders upon reduction of a dithiadiazolium salt. Bis- and tris-(l,3,2,4-dithiadiazolyl)s were shown by ESR to undergo rearrangement in solution to the more stable 1,2,3,5-dithiadiazolyl isomer (containing the -CNSSN ring). Preparation of the l,3,5-rm-(l,3,2,4-dithiadiazolium) iodide [C6H3-1,3,5-(CNSNS)(_3)][I](_3)] in an ESR tube gave a series of ESR spectra similar to those observed for dithiadiazolyl radicals. Reduction of the l,3,5-rm-(l,3,2,4-dithiadiazolium) cation [C(_6)H(_3)-1,3,5-(CNSNS)3](^3+) gave a material identified by elemental analysis as l,3,5-tris-(dithiadiazolyl). Reoxidation of this material with bromine gave a tris-(tribromide) salt [C(_6)H(_3)-1,3,5-(CN(_2)S(_2))(_3)] [Br(_3)](_3). In the same way, reoxidation of the bis-(dithiadiazolyl) [C(_6)H(_4)-1,3-(CN(_2)S(_2))(_2)] gave a bis- (tribromide) [C(_6)H(_4)-l,3-(CN(_2)S)(_2)][Br(_3)]2.1,3,2,4-dithiadiazolium cations were found to initiate the cationic ring-opening polymerization of tetrahydrofuran, and samples of high molecular weight po/y(THF) with low polydispersity initiated by [PhCNSNS][AsF(_6)] and [C(_6)H(_3)-l,3,5-(CNSNS)(_3)][AsF(_6)](_3) were prepared and studied. The reaction of 1,3,2,4-dithiadiazoUum salts with water was studied, and it was shown by infrared and NMR spectroscopy that one dithiadiazolium ring reacts with two equivalents of water, with a 1:1 reaction compound not being formed. The 1,2,3,5-dithiadiazolyl dimer (PhCNSSN)(_2) was found to dechlorinate the activated quinone o-chloranil to give [PhCNSSN]Cl and a quinone coupling product