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The crystalline perchlorate and trichlorodiiodide of the thianthrene cation radical, CIZH,S* %IO,-, and CIZH, Sp+12Cls-, have been prepared. With these salts it has been possible to study the reactions of the thianthrene cation radical with water, iodide ion, chloride ion, triphenylamine, and, to some extent, the vinyl monomers styrene, a-methylstyrene, ethyl vinyl ether, 1,l-diphenylethylene, acrylonitrile, and methyl methacrylate. Electron transfer to the thianthrene cation radical is facile, depending on the relative redox potentials of the cation radical and the other reactant. The reaction of the perchlorate salt with water has been studied in detail. The products are equal amounts of thianthrene and thianthrene 5-oxide. Kinetic work shows that the water reacts with the dication, formed by disproportionation of the cation radical, rather than with the cation radical itself. The longer known reactions of the thianthrene cation radical in sulfuric acid solution are now clearly underst andable.

Thianthrene cation radical salts, Th(*)(+) X(-)(X(-) = a, ClO(4)(-); b, PF(6)(-); c, SbF(6)(-)), add to cycloalkenes (C(5)-C(8)) in acetonitrile (MeCN) to form 1,2-bis(5-thianthreniumyl)cycloalkane salts and 1,2-(5,10-thianthreniumdiyl)cycloalkane salts, most of which have now been isolated and characterized. These are called bis- (3, 6, 9, 12) and monoadducts (4, 7, 10, 13). The proportional amount of the monoadduct obtained in the initial stage of the reaction varied with the cycloalkene in the order C(6) << C(5) < C(7) << C(8). Thus, the ratio bis:mono for C(5) and C(7) was, respectively, about 80/20 and 50/50. In contrast, only about 5% of the C(6) monoadduct (7a) and none of 7b,c was obtained, while for C(8) none of the bisadducts 12a-c was found. Bisadducts 3 and 9 lost thianthrene (Th) slowly in MeCN solution and changed into monoadducts 4 and 10. A comparable change from 6a into 7a was not observed. The monoadducts, themselves, lost a proton slowly in dry MeCN and opened into 1-(5-thianthreniumyl)cycloalkenes (5, 8, 11, 14). With 3 and 9, particularly, it was possible to follow with NMR spectroscopy the succession of changes, for example, 3 to 4 to 5. The opening of a monoadduct was made faster by adding a small amount of water to the solution. The bisadducts of 4-methylcyclohexene (15a) and 1,5-cyclooctadiene (17a) were isolated and characterized. Although a small amount of monodduct (16a) of 4-methylcyclohexene was found with NMR spectroscopy, it could not be isolated. Bis- and monoadducts were obtained also in additions of Th(*)(+) ClO(4)(-) to acyclic alkenes, in relative amounts that, again, varied with the alkene. From cis-2-butene the dominant product was the bisadduct (18), while the monoaduct (19) was characterized with NMR spectroscopy but could not be isolated. In contrast, trans-3-hexene gave mainly the monoadduct (21), while the bis adduct (20) could not be isolated. With 4-methyl-cis-2-pentene, both bis- (22) and monoadduct (23) were isolated, the former being dominant. The conversion of 18 into 19 was characterized with NMR spectroscopy. In all cycloalkene bisadducts, the configurational relationship of the two thianthrenium groups was trans, while in the monoadducts, the bonds to the single thianthrene dication were (necessarily) cis. In both bis- and monoadducts of acyclic alkenes, the configuration of the alkene was retained. The mechanisms of addition with retention of configuration, of conversion of a bis- into a monoadduct, and of opening of a monoadduct are discussed. Products were identified with a combination of NMR spectroscopy, X-ray crystallography, elemental analysis, and (for cycloalkene adducts) reaction with thiophenoxide ion.

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