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

Two efficient processes for the synthesis of 12 relatively water-soluble binary triazolium and the first tetrazolium borane [B(12)H(12)] and carborane [CB(11)H(12)] 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 afforded excellent recovery for a broad series of otherwise water-soluble heterocyclium salts. Second, an alternative aqueous metathesis, driven to completion by precipitation of silver halides, followed by removal of water, redissolution in acetonitrile, and filtration through a silica-gel plug, also yielded such heterocyclium borane and carborane salts. Mixed 1:1 dication heterocyclium borane salts were first synthesized using this second procedure, and one example showed melting-point depression behavior.