Dodecamethylcarba-closo-dodecaborate(-) anion, CB(11)Me(12)(-)

Very weakly nucleophilic anions have been of interest for many applications, such as optimization of ionic electrolytes, stabilization of unusual cations, production of weakly ligated (`naked') cations in solution for Lewis acid catalysis of polymerization, pericyclic and other reactions etc. We report a simple two-step synthesis of the icosahedral dodecamethylcarba-closo-dodecaborate(-) anion (1, CB11Me12-) which meets the structural criteria, but still falls a little short in items of oxidizability and acid resistance. Salts of 1 appear to be very stable to air, bases (several days in saturated KOH/EtOH), and dilute acids (overnight in 5% H2SO4/EtO2), but destroyed after several hours in concentrated H2SO4 or CF3SO3H. The solubility of the hydrated Li+ salt of 1 is extreme in polar solvents, very high in chloroform, and fair in carbon tetrachloride and toluene.