C-Halogenation of the closo-[CB11H12]- Anion

Abstract

A synthesis is described of the four C-halogenated 1-X-CB11H11- anions (X = I, Br, Cl, F) using N-halosuccinimides and N-fluorobis(benzenesulfonyl)amine as halogenating agents. The procedure yields only the desired product next to unreacted starting material. Regularities in the 11B and 13C NMR chemical shifts of singly halogenated icosahedral carboranes are summarized.

Chemistry of the Carba-closo-dodecaborate(−) Anion, CB11H12-

“…What is most needed at present is a high-yield one-step or two-step synthesis from cheap bulk chemicals. As we shall see in section 7, starting with bulk chemicals, at this time some 29 Ph H H I 162 36 Me Me Me OMe 196 13 TIPS H H I 163 36 Me Me Me OH 197 44 Me H Cl Cl 164 21 HS H H H 198 44 Me H Br Br 165 21 MeS H H H 199 14 Me H I I 166 21 Me2S + H H H 200 40 Me F F F 167 21 H H H M e 2S 201 45 Me Cl Cl Cl 168 21 H H H X g 202 41 Me Br Br Br 169 37 F H H H 203 41 Me Me 179 39 H H I I 213 15 Me Me Me F 180 40 H F F F 214 47 Me Me Me I 181 41 H C l C l C l 215 13 Me Me I Me 182 41 H B r B r B r 216 13 Me I Me Me 183 41 H I I I 217 13 Me Me I I 184 41 Br Br Br Br 218 48 F H Me Me 185 42 Me3N + H H I 219 48 Cl H Me Me 186 31 X d H H I 220 48 Cl Me Me Me 187 43 NH3 + H I I 221 48 Br Me Me Me 188 43 NH3 + I I I 222 48 I M e M e M e 189 14 H B r C l C l 223 49 H O H B r B r 190 14 H I Cl Cl 224 16 H H H X h 191 14 H C l B r B r 225 16 H H H X i 192 …”

Preparation of undecamethylated and hexamethylated 1‐halocarba‐closo‐dodecaborate anions

“…According to procedure P3, 2b (0.50 g, 1.61 mmol) was methylated using MeOTf and CaH 2 in sulfolane at RT for 18 days to give a crude brown solid which was recrystallized from MeOH/water (1:9) to give the cesium salt of 3b (0.62 g, 83%), whose spectra were identical with those reported earlier [17]. Chemical shifts of the methyl carbon atoms have now also been obtained: [28] (0.22 g, 1 mmol) in 3.6 mL of sulfolane (4.8 g, 40 mmol, freshly distilled from CaH 2 ) was stirred at room temperature under argon with methyl triflate (2.3 mL, 3.3 g, 20 mmol) in the presence of CaH 2 (1.7 g, 40 mL). The reaction was monitored by ESI/MS.…”

“…The solvent of the combined organic layers was removed under reduced pressure to give a solid that was dried under reduced pressure. [28]. At −20…”

“…After evaporation of the organic layers, the resulting solid was purified by reverse phase column chromatography using buffered water/methanol eluent (55% methanol, 45% water, each containing 0.7% of Et 3 N and 1% AcOH) to give the cesium salt of 2b (470 mg, 84%). [28]. At −20…”

“…We have since managed to overcome the obstacles and presently describe an efficient conversion of the four known [28] The permethylated 1-halocarborate anions 3b-3d were prepared by the methylation of the cesium salts of 2b-2d in sulfolane with methyl triflate in the presence of CaH 2 as the base. Considerable patience was the key to success, as the reactions go to completion very slowly: 18 days for 2b, 25 days for 2c, and 42 days for 2d.…”