The synthesis and reactivity of some 1,2,3,5 - and 1,3,2,4-dithiadiazolium salts

Abstract

The reaction of N(SCI)2(^+) salts with SnCl(_2) provided a new route to the SNS(^+) synthon; an important reagent in the synthesis of inorganic sulphur-nitrogen containing heterocycles. The reactions of C(_6)H(_5)CN and C(_6)H(_5)CN with a variety of SNS(^+) salts (AsF(_6)-, SbCl(_6)" and AICI(_4)-) were examined. Both [SNS]AsF(_6)] and [SNS][SbCI(_6)] reacted in high yield to give the 1,3,2,4-dithiadiazolium salts (Ar.CNSNS(^+)) whereas [SNS][AICI(_4)] did not readily provide the analagous heterocycle. Reduction of these 1,3,2,4-dithiadiazolium cations provided the isostructural 1,3,2,4-dithiadiazole radicals which then underwent rearrangement to the 1,2,3,5-dithiadiazole. This isomerisation process was monitored by e.s.r. spectroscopy. Reaction of two or three equivalents of[SNS][AsF(_6)] with dicyanoaromatics (o,m and p- C(_6)H(_4)(CN)(_2), NC.C(_6)H(_4).C(_6)H(_4).CN and p-C(_6)F(_4)(CN)(_2)) or 1,3,5-tricyanobenzene yielded the novel bis- and tris-(dithiadiazolium) cations respectively. 1,4-phenylene bis(1-,3,2,4-dithiadiazolium) hexafluoroarsenate(V) was readily converted to a variety of other salts by anion metathesis and its reduction yielded the neutral bis(dithiadiazole) which was characterised by a single crystal X-ray structure determination. Reaction of 4-phenyl-1,2,3,5-dithiadiazolium hexafluoroarsenate(V) with [Et(_4)N][Pt(mnt)(_2)] and [Et(_4)N](_2)[Pt(mnt)(_2)] produced [PhCN(_2)S(_2)][Pt(mnt)(_2)] and [PhCN(_2)S(_2)](_2)[Pt(mnt)(_2)] respectively; the latter compound was characterised by an X- ray structure. The reaction of [PhCN(_2)S(_2)]CI with [Et(_4N][Pt(mnt)(_2)] in the presence of excess [PhCN(_2)S(_2)]CI yielded [(PhCN(_2)S(_2))(_2)CI][Pt(mnt)(_2)] . Crystals of the analogous compound, [(p-Cl.C(_6)H(_4).CNSSN)(_2)CI][Pt(mnt)(_2)] , were large enough for an X-ray structure determination and this provided the second example of the planar cation, [(ArCN(_2)S(_2))(_2)CI](^+).In comparison the reaction of phenyldithiadlazole, (PhCN2S2)2. with Pd(PPh(_3))(_4) led to the formation of Pd(_3)(PhCN(_2)S(_2))(_2)(PPh(_3))(_3); the solid state structure of which shows three square planar Pd centres held together by two bridging PhCN(_2)S(_2) ligands.