| Summary: | 9-Dimethyloxonium, 10-dimethyloxonium, 9-methoxy and 10-methoxy derivatives of <i>nido</i>-carborane (9-Me<sub>2</sub>O-7,8-C<sub>2</sub>B<sub>9</sub>H<sub>11</sub>, 10-Me<sub>2</sub>O-7,8-C<sub>2</sub>B<sub>9</sub>H<sub>11</sub>, [9-MeO-7,8-C<sub>2</sub>B<sub>9</sub>H<sub>11</sub>]<sup>−</sup>, and [10-MeO-7,8-C<sub>2</sub>B<sub>9</sub>H<sub>11</sub>]<sup>−</sup>, respectively) were prepared by the reaction of the parent <i>nido</i>-carborane [7,8-C<sub>2</sub>B<sub>9</sub>H<sub>12</sub>]<sup>−</sup> with mercury(II) chloride in a mixture of benzene and dimethoxymethane. Reactions of the 9 and 10-dimethyloxonium derivatives with triethylamine, pyridine, and 3-methyl-6-nitro-1<i>H</i>-indazole result in their N-methylation with the formation of the corresponding salts with 9 and 10-methoxy-<i>nido</i>-carborane anions. The reaction of the symmetrical methoxy derivative [10-MeO-7,8-C<sub>2</sub>B<sub>9</sub>H<sub>11</sub>]<sup>−</sup> with anhydrous FeCl<sub>2</sub> in tetrahydrofuran in the presence of <i>t</i>-BuOK results in the corresponding paramagnetic iron bis(dicarbollide) complex [8,8′-(MeO)<sub>2</sub>-3,3′-Fe(1,2-C<sub>2</sub>B<sub>9</sub>H<sub>10</sub>)<sub>2</sub>]<sup>−</sup>, whereas the similar reactions of the asymmetrical methoxy derivative [9-MeO-7,8-C<sub>2</sub>B<sub>9</sub>H<sub>11</sub>]<sup>−</sup> with FeCl<sub>2</sub> and CoCl<sub>2</sub> presumably produce the 4,7′-isomers [4,7′-(MeO)<sub>2</sub>-3,3′-M(1,2-C<sub>2</sub>B<sub>9</sub>H<sub>10</sub>)<sub>2</sub>]<sup>−</sup> (M = Fe, Co) rather than a mixture of <i>rac</i>-4,7′- and <i>meso</i>-4,4′-isomers.
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