1,7-(SMe(2))(2)B12H10, 1,12-(SMe(2))(2)B12H10, and [SMe(3)][B12H11(SMe(2))] were prepared and isolated from the self-condensation reaction of BH3 . SMe(2) in the absence of a solvent. At 150 degrees C the reaction yields, primarily, two isomers : 1,7-(SMe(2))(2)B12H10, the major component, and 1,12-(SMe(2))(2)B12H10 the minor component, that are separated by thin layer chromatography. Single-crystal X-ray structure determinations were performed for both isomers, confirming the structures inferred from H-1, B-11, and B-11{H-1}-B-11{H-1} (COSY) NMR spectra. Crystal data for 1,7-(SMe(2))(2)B12H10 : trigonal P3(2)21, a = 12.901(10) Angstrom, b = 12.901(10) Angstrom, c = 23.73(2) Angstrom, gamma = 120 degrees, Z = 9. Crystal data for 1,12-(SMe(2))(2)B12H10 : orthorhombic Pbca, a = 10.101(2) Angstrom, b = 11.220(2) Angstrom, c = 13.464(2) Angstrom, Z = 4. At 60 degrees C, the self-condensation of BH3 . SMe(2) is very slow, but yields [SMe(3)][B12H11(SMe(2))] as the major product. Multinuclear and 2-dimensional NMR spectra are in full accord with the structure determined by X-ray methods. Crystal data for [SMe(3)][B12H11(SMe(2))]. MeCN : monoclinic P2(1), a = 8.904(10) Angstrom, b = 9.08(2) Angstrom, c = 12.39(3)Angstrom, beta = 93.820, Z = 2.