The trimethylammonium salt of mercapto-closo-carborane 1 was prepared by known method [47]. Tetrahydrofuran was dried by distillation over metallic sodium in the presence of benzophenone, according to a standard procedure [55]. 1,2-Dibromoethane, 1,3-dibromopropane, dimethylamine, ethanol, dichloromethane, acetonitrile, and ethyl acetate were purchased from commercial suppliers and used without preliminary purification. A saturated (~2.3 M) solution of dimethylamine in THF was prepared by adding Me2NH, condensed under cooling, to dry tetrahydrofuran.

The reaction progress was monitored by thin-layer chromatography on Kieselgel 60 F245 plates (Merck); a 0.5% solution of PdCl2 in methanol with 1% HCl was used for visualization. Column chromatography was performed using Acros Organics silica gel (0.060–0.200 mm). 1H, 11B, 11B, 13C NMR spectra and (HH)gCOSY and (HC)HSQC correlation spectra were recorded on a Varian Inova 400 spectrometer in acetone-d6. For 1H and 13C NMR spectra, chemical shifts are given relative to Me4Si; for 11B and 11B NMR spectra, chemical shifts are given relative to BF3Et2O. IR spectra were recorded on an FSM2201 instrument (INFRASPEC). High-resolution mass spectra (HRMS) were recorded on a Bruker micrOTOF II and an LCMS-9030 (Shimadzu, Japan) using electrospray ionization (ESI-MS) in the mass range m/z 50–1500.

Synthesis of 1-BrCH2CH2S-1,2-C2B10H11 (2). To a solution of 1,2-dibromoethane (5.5 mL, 63.81 mmol) in ethanol (40 mL), a solution of the trimethylammonium salt of mercapto-closo-carborane 1 (0.50 g, 2.12 mmol) in ethanol (40 mL) was added dropwise over 1 h. The resulting mixture was stirred with gentle heating for about 2 h, then cooled and evaporated on a rotary evaporator. The target product was isolated by extraction with methylene chloride (3 × 20 mL) from water (30 mL). The organic fractions were combined and evaporated under reduced pressure, yielding compound 2 as a viscous yellowish oil (0.49 g, 82%). IR spectrum (film), ν, cm–1: 3071 (C–H), 2967 (C–H), 2935 (C–H), 2591 br (B–H), 2585 (B–H), 1418, 1257, 1199, 1073, 877, 722. 1H NMR spectrum, δ, ppm: 4.86 s (1H, CcarbH), 3.67 t (2H, SCH2CH2Br, J 7.5 Hz), 3.46 t (2H, SCH2CH2Br, J 7.5 Hz), 3.0–1.4 m (10H, BH). 13C NMR spectrum, δC, ppm: 74.7 (CcarbS), 68.5 (CcarbH), 38.6 (SCH2CH2Br), 29.2 (SCH2CH2Br). 11B NMR spectrum, δB, ppm: –1.9 d (1B, J 152.0 Hz), –5.3 d (1B, J 151.0 Hz), –9.4 d (4B, J 138.0 Hz), –12.3 d (4B, J 160 Hz).

Synthesis of 1-BrCH2CH2CH2S-1,2-C2B10H11 (3) was prepared similarly using the trimethylammonium salt of mercapto-closo-carborane 1 (0.50 g, 2.12 mmol) in ethanol (40 mL) and 1,3-dibromopropane (6.5 mL, 64.03 mmol) in ethanol (40 mL). Yield 0.52 g (86%), viscous yellowish oil. IR spectrum (film), ν, cm–1: 3130 (C–H), 3071 (C–H), 2969 (C–H), 2937 (C–H), 2604 br (B–H), 2589 br (B–H), 1424, 1257, 1202. 1H NMR spectrum, δ, ppm: 4.83 s (1H, CcarbH), 3.57 t (2H, SCH2CH2CH2Br, J 7.5 Hz), 3.17 t (2H, SCH2CH2CH2Br, J 7.5 Hz), 2.17 quintet (2H, SCH2CH2CH2Br, J 7.5 Hz), 3.0–1.5 m (10H, BH). 13C NMR spectrum, δC, ppm: 75.3 (CcarbS), 68.5 (CcarbH), 35.2 (SCH2CH2CH2Br), 31.5 (SCH2CH2CH2Br), 31.3 (SCH2CH2CH2Br). 11B NMR spectrum, δB, ppm: –2.1 d (1B, J 147.0 Hz), –5.4 d (1B, J 147.0 Hz), –9.4 d (4B, J 134.0 Hz), –12.1 d (2B, J 157.0 Hz), –12.5 d (2B, J 165.0 Hz).

Synthesis of 7-Me2HNCH2CH2S-7,8-C2B2H11(4) and H[(7,8-C2B9H11-7-SCH2CH2)2NMe2] (5). To 10 mL of a saturated (~2.2 M) solution of dimethylamine in tetrahydrofuran at –5°C, a solution of compound 2 (0.30 g, 1.06 mmol) in tetrahydrofuran (10 mL) was added dropwise over 15 min. The mixture was stirred at room temperature for 2 h. The solution was evaporated under reduced pressure. A mixture of products 4 and 5 was obtained, which were separated by column chromatography on silica gel using a mixture of acetonitrile and ethyl acetate (1:4) as the eluent.

Compound 4. Yield 0.10 g (41%), white crystalline powder. IR spectrum (film), ν, cm–1: 3205 (N–H), 3155 (N–H), 3051 (C–H), 2978 (C–H), 2947 (C–H), 2524 br (B–H), 1617, 1466, 1418, 1232, 1028, 880, 746. 1H NMR spectrum, δ, ppm: 3.67 m (1H, SCH2CH2N), 3.52 m (1H, SCH2CH2N), 3.26 m (1H, SCH2CH2N), 3.23 s (6H, NMe2), 3.05 m (1H, SCH2CH2N), 1.93 s (1H, CcarbH), 3.0 to –0.3 m (8H, BH), –2.91 m (1H, BHB). 13C NMR spectrum, δC, ppm: 58.1 (SCH2CH2N), 51.0 (CcarbH), 43.3 (NMe2), 30.4 (SCH2CH2N). 11B NMR spectrum, δB, ppm: –9.1 d (1B, J 138.0 Hz), –11.0 d (1B, J 136.0 Hz), –14.6 d (1B, J 128.0 Hz), –15.3 d (1B, J 110.0 Hz), –18.4 d (2B, J 138.0 Hz), 21.2 d (1B, J 153.0 Hz), –32.5 d. d (1B, J 135.0, 37.0 Hz), –36.4 d (1B, J 137.0 Hz). Mass spectrum (ESI HRMS), m/z: 237.2282 [M – H]– (calcd for C6H22B9NS: 237.2279).

Compound 5. Yield 0.13 g (28%), white crystalline powder. IR spectrum (film), ν, cm–1: 3038 (C–H), 2989 (C–H), 2840 (C–H), 2532 br (B–H), 1622, 1457, 1423, 1375, 1220, 1028, 885, 746. 1H NMR spectrum, δ, ppm: 3.87 m (2H, SCH2CH2N), 3.59 m (2H, SCH2CH2N), 3.47 s (6H, NMe2), 3.40 m (2H, SCH2CH2N), 3.11 m (2H, SCH2CH2N), 1.98 s (1H, CcarbH), 3.0 to –0.4 m (8H, BH), –2.89 m (1H, BHB). 13С NMR spectrum, δC, ppm: 65.0 (SCH2CH2N), 52.1 (CcarbH), 50.8 m (NMe2), 29.2 (SCH2CH2N). 11B NMR spectrum, δB, ppm: –9.4 d (1B, J 151.0 Hz), –11.1 d (1B, J 140.0 Hz), –15.4 d (2B, J 130.0 Hz), –17.7 d (1B, J 155.0 Hz), –18.6 d (1B, J 127.0 Hz), –21.1 d (1B, J 153.0 Hz), –32.5 d. d (1B, J 128.0, 39.0 Hz), –36.3 d (1B, J 137.0 Hz). Mass spectrum (ESI HRMS), m/z: 429.4075 [M]– (calcd for C10H36B18NS2–: 429.4088).

7-Me2HNCH2CH2CH2S-7,8-C2B9H11(6). The reaction was carried out according to the method described above for the synthesis of 4, using 10 mL of a saturated solution of dimethylamine in tetrahydrofuran and a solution of compound 3 (0.31 g, 1.04 mmol) in tetrahydrofuran (10 mL). The target product was isolated by column chromatography on silica gel using a mixture of acetonitrile and ethyl acetate (1:4) as the eluent. Yield 0.17 g (64%), white crysstals. IR spectrum (film), ν, cm–1: 3150 (N–H), 3051 (С–H), 2952 (C–H), 2930 (C–H), 2860 (C–H), 2533 br (B–H), 1481, 1465, 1415, 1028, 996, 958. 1H NMR spectrum, δ, ppm: 3.51 m (2H, SCH2CH2CH2N), 3.23 s (6H, NMe2), 2.98 m (1H, SCH2CH2CH2N), 2.56 m (1H, SCH2CH2CH2N), 2.20 m (1H, SCH2CH2CH2N), 2.07 m (1H, SCH2CH2CH2N), 1.94 s (1H, CcarbH), 3.0 to –0.5 m (8H, BH), –2.87 m (1H, BHB). 13C NMR spectrum, δ, ppm: 57.5 (SCH2CH2CH2N), 52.7 (CcarbH), 43.3 (NMe2), 33.0 (SCH2CH2CH2N), 25.4 (SCH2CH2CH2N). 11B NMR spectrum, δB, ppm: –9.7 d (1B, J 133.0 Hz), –10.7 d (1B, J 131.0 Hz), –14.8 d (1B, J 141.0 Hz), –17.1 d (3B, J 140.0 Hz), –21.8 d (1B, J 149.0 Hz), 32.8 d (1B, J 121.0, J 40.0 Hz), –36.5 d (1B, J 133.0 Hz). Mass spectrum (ESI HRMS), m/z: 275.2401 [M + Na]+ (calcd for C7H24B9NS: 275.2402), 251.2431 [M]– (calcd for C7H23B9NS: 251.2437).