STUDIES ON THE ELECTROACTIVE HETEROCYCLES C6S80 2- AND C6S6O20/2- ANDRELATED METAL-COMPLEXES/

The properties of the carbon sulfide C6S8 (1) as well as its dioxo ana logue C6S6O2 (2) have been studied in the fully oxidized and fully red uced forms, i.e., 1(0), 1,(2-) 2(0), 2(2-). A crystallographic study s hows that compound 2 is a tricyclic species with a twisted 1,2-dithiin (unsaturated C4S2 ring) core. Reduction of 1 with 2 equiv of LiBHEt3 gave C6S82- (1(2-)), which was isolated as its PP4+ salt. A crystallog raphic study of this salt shows that reduction has resulted in cleavag e of the S-S bond and that, in the solid state, the dihedral angle bet ween the two rings is 180 degrees. Both 1(2-) and 2(2-) undergo two se quential and reversible 1e(-) oxidations near 0 V (vs Ag/AgCl), thus e stablishing that 1(0) and 2(0) are good oxidants relative to other dis ulfides. Treatment of (PPh4)(2)[C6S8] with [Ni(H2O)(6)]Cl-2 afforded t he dark red (PPh4)(2)[Ni(C6S8)(2)] (3). The analogous Pt complex (4) w as also prepared. Crystallographic analysis of 3 shows that the nickel center is square planar, comprising two seven-membered NiS2C4 rings. The paramagnetism observed for solutions of 3 are attributed to the fo rmation of a tetrahedral isomer.