Pairing Heterocyclic Cations with closo-Icosahedral Borane and Carborane Anions. II. Benchtop Alternative Synthetic Methodologies for Binary Triazolium and Tetrazolium Salts with Significant Water Solubility

摘要

Two efficient processes for the synthesis of twelve, relatively water soluble, heterocyclium closo-dodecaborane (B12H12)-2 and closo-dodecacarborane (CB11H12)-1 salts by a one-step, open-air metathesis reaction have been developed. First, a combination of exhaustive trituration of the two solid reactant salts with refluxing anhydrous acetonitrile followed by flash filtration through a plug of silica gel affords excellent recovery for a broad series of otherwise water-soluble salts. Second, an alternative aqueous metathesis, driven to completion by precipitation of silver halides, followed by removal of water, re-dissolution in acetonitrile, and filtration through a plug of silica gel, affords complex heterocyclium borane salts albeit with possible minor 'bleed-through' of the by-product KNO3 salt. Mixed cation heterocyclium dodecaborane salts also can synthesized and one example analyzed, shows melting point depression behavior.