mixture was stirred overnight. CH3CN was removed by a flow of N2 flow. The resulting mixture was extracted three times with CH2Cl2. The combined organic layers were washed once with Milli-Q water to remove the last traces of lithium salts, dried on Na2SO4, evaporated to dryness using a rotary evaporator, and further dried under vacuum (6 mbar, then 0.01 mbar). 1Isopropyl-3-propylimidazolium NTf2 and 1,3-diisopropylimidazolium NTf2 were obtained as colorless liquids, 1,3-di-tert-butylimidazolium NTf2 as a white solid, in yields of 99%. 1-Isopropyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide. 1H NMR (CD3CN, 400 MHz): (ppm) = 0.92 (t, CH3, 3H), 1.51 (d, CH3, 6H), 1.87 (m, CH2, 2H), 4.09 (t, N-CH2, 2H), 4.59 (m, CH, 1H), 7.41 (s, H-4 or H-5, 1H), 7.48 (s, H-4 or H-5, 1H), 8.51 (H-2, s, 1H). 13C NMR (CD3CN, 100 MHz): (ppm) = 11.17 (CH2CH3), 23.18 (CH3), 24.37 (CH2), 52.52 (N-CH2), 54.55 (CH), 116.57 (CF3), 119.76 (CF3), 121.93 (C-4 or C-5), 122.94 (CF3), 123.89 (C-4 or C-5), 126.13 (CF3), 135.33 (C-2). 19F NMR (CD3CN, 376 MHz): (ppm) = −80.09 (s, CF3). 1,3-Diisopropylimidazolium bis(trifluoromethylsulfonyl)imide. 1H NMR (CD3CN, 400 MHz): (ppm) = 1.51 (d, CH3, 12H), 4.58 (m, CH, 2H), 7.47 (s, H-4+H-5, 2H), 8.53 (H-2, s, 1H). 13C NMR (CD3CN, 100 MHz): (ppm) = 23.18 (CH3), 54.58 (CH), 116.57 (CF3), 119.76 (CF3), 121.96 (C-4+C5), 122.94 (CF3), 126.13 (CF3), 134.07 (C-2). 19F NMR (CD3CN, 376 MHz): (ppm) = −80.08 (s, CF3). 1,3-Di-tert-butylimidazolium bis(trifluoromethylsulfonyl)imide. 1H NMR (CD3CN, 400 MHz): (ppm) = 1.62 (s, C(CH3)3, 18H), 7.57 (s, H-4+H-5, 2H), 8.42 (H-2, s, 1H). 13C NMR (CD3CN, 100 MHz): (ppm) = 30.10 (CH3), 61.56 (CH), 116.57 (CF3), 119.75 (CF3), 121.63 (C-4+C-5), 122.94 (CF3), 126.13 (CF3), 132.88 (C-2). 19F NMR (CD3CN, 376 MHz): (ppm) = −80.17 (s, CF3). 1,3-Dimethyl-2,4,5-trideuteroimidazolium bis(trifluoromethylsulfonyl)imide. A mixture of 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide (5.0 g, 13.25 mmol), D2O (6.0 mL, 0.332 mol) and triethylamine (0.1 mL, 0.72 mmol) was stirred at 65 °C for four days under N2. After cooling, D2O and Et3N were removed under vacuum, fresh D2O (6.0 mL) and triethylamine (0.1 mL, 0.72 mmol) were added, and stirring at 65 °C was continued for another four days. After a total of six heating-evaporation cycles, D2O and Et3N were removed under vacuum and the liquid residue was dissolved in CH2Cl2 and dried on Na2SO4. The dichloromethane was evaporated on a rotary evaporator, the residue was redissolved in 20 mL dichloromethane, passed through a regenerated cellulose membrane filter (pore size 0.2 µm) to remove traces of solids, and then dried under vacuum (6 mbar, then 0.01 mbar), yielding 1,3dimethyl-2,4,5-trideuteroimidazolium bis(trifluoromethylsulfonyl)imide as a colorless liquid
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