The preparation and isolation in the solid state of five aryl 1,2,3,5‐dithia‐ and diselenadiazolyls is reported. The structure of the dimer of 4‐ClC6H4CN2S2 in the solid state was obtained: monoclinic, C2/c with Z = 8, a = 20.982(10), b = 10.058(3), c = 15.867(6) Å, β = 93.34(4)°, R = 0.066, Rw = 0.053 for 1 099 data. Cyclic voltammetry shows reversible oxidation to a 6π cation for all 10 compounds in both CH2Cl2 and CH3CN; reversible reduction to an 8π anion is observed in CH2Cl2 for all except X = CF3, E = S. The reductions are only quasi‐reversible in CH3CN for E = Se. The oxidation process is independent of chalcogen type; the reduction process is found to be about 0.2 V more negative for E = S vs E = Se.

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 XC6H,CN2S2+~1-and Ph,Sb 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-(XC6H,)2{CN2S2N,C), X = H, 4-CH,, 4-CH,O, 4 4 , 4-CF,, and 3-CF,, are reported. Mixed derivatives were also prepared, but not isolated as pure compounds. The crystal structure of the 4-CF, compound has been determined by X-ray diffraction; triclinic, with Z = 1; cell dimensions: a = 6.835(2), b = 9.936(3), c = 6.320(2) A , a = 96.44(3)", P = 102.88(3)", y = 88.42(3)". R = 3.4%, R,,. = 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 10a central aromatic rings have been oxidized and reduced in CHzC1, using voltammetric methods. The reversible one-electron reduction step gives stable 1 l n species. On a dCveloppC de nouvelles voies de synthkse des compos6s mentionnes dans le titre qui donnent des rendements de beaucoup superieurs 2 ceux rapportes anterieurement. Dans une mCthode, la rCaction du O2 avec un melange de HC6H4CN2S2+C1-et de Ph3Sb conduit aux produits avec des rendements allant de 40 a 60%. Dans une autre mCthode, la reaction des mCmes sels avec les amidines silylkes XC6H,C{NSiMe,}N(SiMe,),, dans un rapport molaire de 1 : 1, conduit aux mCmes produits avec des rendements allant de 18 a 65%. Donc on rapporte la synthkse des 3,7-(XC6H,)2{CN2S2N2C), X = H, 4-CH,, 4-CH,O, 4-C1, 4-CF3 et 3-CF3. On a aussi prepare des derives mixtes; toutefois, il n'a pas Cte possible de les isqler 2 I'Ctat pur. On a determine la structure cristallin: du compose 4-CF, par diffraction des rayons X; triclinique, P l , avec a = 8,835(2), b = 9,936(3) et c = 6,320(2) A , a = 96,44(3)", P = 102,88(3)" et y = 88,42(3)", Z = 1. R = 3,4% et R,, = 3.5% pour I100 donnCes. Le cycle a huit chainons est plat alors que les longueurs des liaisons sont Cquivalentes entre tous les atomes pris deux a deux; ce resultat indique que la distribution Clectronique est dClocalisCe. Utilisant des methodes voltampCrometriques et operant dans le CH2C1,, on a oxydC et reduit les cycles aromatiques 2 10 Clectrons a . La reduction reversible par un electron conduit a des espkces stables a 11 electrons n . En accord avec les etudes chimiques anterieures, les composCs mentionnes dans le titre sont beaucoup plus difficiles a oxyger que le 3,7-[(CH3)2Nl2{CNzSzNzC}.[Traduit par la redaction]

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The trends in redox potentials for isovalent series of 5d hexafluoro- and -chlorometalates, [MX6]0/- and [MX6]-/2- (M = Ta to Pt; X = F, Cl), are compared, including the previously unpublished electrochemistry of [IrF6]2-. For a given series, the trend in redox data can be understood in terms of the core charge of the metal and interelectronic terms. However, there is a marked convergence of the electrochemical redox potentials for isovalent series of [MF6] z / z -1 and [MCl6] z / z -1 (z = 0, 1−) complexes. Thus, while the oxidation potential of [TaF6]2- is 1.6 V lower than that of [TaCl6]2-, the oxidation potential of [IrF6]2- is only 0.5 V lower than that of [IrCl6]2-. The redox data correlate well with computed electron affinities of MX6 and [MX6]- derived from density functional calculations. A fragmentation approach is adopted to analyze the electrochemical trends in terms of the properties of the metal center and trends in the metal−halide bonding. The observed convergence in redox data for isovalent [MX6] z / z -1 (x = F, Cl; z = 0, 1−) series is rationalized in terms of the ability of the halide arrays to stabilize the two metal oxidation states involved. The ability of the chloride array to stabilize the higher metal oxidation state increases more rapidly along the third row transition metals than does that of the fluoride array. This counteracts the effects of metal core charge to produce the observed convergence. The computational results indicate that, for the later metals in their highest oxidation states, the redox-active orbital becomes increasingly halide based. In view of this, the stability of the neutral hexahalides with respect to the reductive elimination of X2 was studied, and the results suggest that OsCl6 and IrCl6 are more likely to be stable as novel hexachlorides than PtCl6.