Pairing heterocyclic cations with closo-dodecafluorododecaborate (2−): Synthesis of binary heterocyclium(1+) salts and a Ag4(heterocycle)84+ salt of B12F122−

Eight binary salts that pair triazolium(1+), imidazolium(1+), pyrimidinium(1+), or purinium(1+) cations with the icosahedral closo-dodecafluorododecaborate(2−) anion (B12F122−) were synthesized using open-air benchtop metathesis reactions in water or acetonitrile. The scale of the reactions varied from just milligrams to nearly one gram of the K2B12F12 starting material. Other reaction conditions, the scope of the reaction, and the solubilities for the new salts are discussed. Five [heterocyclium]2[B12F12] salts, which were obtained in yields ranging from 84% to 99%, displayed significantly higher densities than the corresponding previously reported analogous [heterocyclium]2[B12H12] and [heterocyclium][CB11H12] salts. A ninth high-density salt consisted of B12F122− paired with a complex Ag4(triazole)84+ cation. The structures of eight of the nine new compounds were determined by single-crystal X-ray diffraction analysis. The density of five [heterocyclium]2[B12F12] salts was found to increase approximately linearly as the distance between the five-membered-ring heterocyclium(1+) cation centroids decreased. This work demonstrates additional flexibility for the rational design of ionic structures with predictable properties, which will ultimately permit the tailoring of ingredient-response behavior.

Described are the first syntheses and single-crystal X-ray diffraction characterization of eight binary [heterocyclium]2[B12F12] salts and a complex [Ag4(heterocycle)8][B12F12]2 salt.Figure optionsDownload as PowerPoint slideHighlights
► First synthesis of heterocyclium icosahedral perfluoroborane salts: [heterocyclium]2[closo-B12F12].
► Unique salt [Ag4(heterocycle)8][B12F12]2 isolated containing the [Ag4(heterocycle)8]4+ tetracation.
► Open-air benchtop synthesis using standard chemical glassware with H2O or CH3CN solvent.
► Linear correlation between salt density and cat⋯cat separation was discovered by X-ray analyses.