ARYL 1,5-DITHIA-2,4,6,8-TETRAZOCINES - A SYNTHETIC, ELECTROCHEMICAL, AND STRUCTURAL INVESTIGATION

New preparative routes to the title compounds are reported in which the yields are substantially improved over previous methods. In one method, reaction of O2 With a mixture of XC6H4CN2S2+Cl- and Ph3Sb leads to the products in 40-60% yield. In another, the reaction of the same salts with silylated amidines XC6H4C{NSiMe3}N(SiMe3)2 in a 1:1 mol ratio leads to the same compounds in 18-65% yield. The syntheses of 3,7-(XC6H4)2{CN2S2N2C}, X = H, 4-CH3, 4-CH3O, 4-Cl, 4-CF3, and 3-CF3, are reported. Mixed derivatives were also prepared, but not isolated as pure compounds. The crystal structure of the 4-CF3 compound has been determined by X-ray diffraction; triclinic, P1BAR with Z = 1; cell dimensions: a = 6.835(2), b = 9.936(3), c = 6.320(2) angstrom, alpha = 96.44(3)degrees, beta = 102.88(3)degrees, gamma = 88.42(3)degrees. R = 3.4%, R(w) = 3.5% for 1100 data. The eight-membered ring is flat with equivalent bond lengths between any two types of atoms, indicative of a delocalized electron distribution. The 10pi central aromatic rings have been oxidized and reduced in CH2Cl2 using voltammetric methods. The reversible one-electron reduction step gives stable 11pi species. The resistance to oxidation of the title compounds is contrasted to the ease of oxidizing 3,7-[(CH3)2N]2{CN2S2N2C}, in accordance with earlier chemical studies.