Synthesis of (TDAE)(O2SSO2)(s) and Discovery of (TDAE)(O2SSSSO2)(s) Containing the First Polythionite, [O2SSSSO2]2鈥?/sup>
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Gaseous SOb>2b> reacts with tetrakis(dimethylamino)ethylene (TDAE) in acetonitrile in a 2:1 stoichiometric ratio to give analytically pure insoluble purple (TDAE)(Ob>2b>SSOb>2b>) (<b>1b>) in about 80% yield. Crystals of (TDAE)(Ob>2b>SSSSOb>2b>) (<b>2b>) were obtained from orange solution over the purple solid. The Raman spectrum of [TDAE]2+ was established using (TDAE)(A) salts [A = 2Br鈥?/sup>, 2Br鈥?/sup>路2Hb>2b>O (X-ray), 2[Brb>3b>]鈭?/sup> (X-ray)]. Vibrational spectroscopy showed that [Ob>2b>SSOb>2b>]2鈥?/sup> in <b>1b> has Cb>2hb> geometry. The X-ray structure of <b>2b> showed that it contained [Ob>2b>SSSSOb>2b>]2鈥?/sup>, the first example of a new class of sulfur oxyanions, the polythionites. The geometry of [Ob>2b>SSSSOb>2b>]2鈥?/sup> consists of Sb>2b> with an S鈥揝 bond length of 2.003(1) 脜 connected to two terminal SOb>2b> moieties by much longer S鈥揝 bonds of 2.337(1) 脜. Calculations (B3PW91/6-311+G(3df)) show that the structural units in [Ob>2b>SSSSOb>2b>]2鈥?/sup> are joined by the interaction of electrons in two mutually perpendicular 蟺* SOMOs of the triplet-state diradical Sb>2b> with unpaired electrons in the 蟺*-antibonding orbitals of the two terminal [SOb>2b>]鈥⑩€?/sup> and polarized to delocalize the negative charge equally onto the three fragments. Thermodynamic estimates show <b>2b> to be stable with respect to loss of sulfur and formation of <b>1b>, in contrast to [Ob>2b>SSSSOb>2b>]2鈥?/sup> salts of small cations that are unstable toward the related dissociation. Reaction of TDAE with an excess of liquid SOb>2b> led to (TDAE)(Ob>3b>SOSOb>3b>)路SOb>2b> (preliminary X-ray, Raman), (TDAE)(Ob>3b>SSSSOb>3b>)路2SOb>2b> (preliminary X-ray, Raman), and (TDAE)(Ob>3b>SSOb>2b>) (Raman).

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