Pairing Heterocyclic Cations with closo-Icosahedral Borane and Carborane Anions. I. Benchtop Aqueous Synthesis of Binary Triazolium and Imidazolium Salts with Limited Water Solubility (Preprint)

摘要

Tailoring the chemical and physical properties of molecular materials by rational design to increase density, reduce toxicity, or to improve overall stability characteristics continues to be an important research endeavor. Achieving this by the structural modification of neutral organic compounds offers a limited scope of opportunities. Organic-like solid and liquid salts significantly enhance this flexibility for properties tailoring by pairing different classical heterocyclic cations with a plethora of different counteranions. Over the past 25 years, this is re-emphasized with salts based on neutral heterocyclic compounds. Rekindled interest in this approach appears to initiate with the unique properties exhibited by the hygroscopic binary 1- ethyl-3-methyl-1,3-imidazolium (EMIM) chloroaluminate salt followed by a subsequent report of non-hygroscopic, air stable, binary EMIM salts containing other anions. Later, triazolium cations are used to form salts with common anions. We now report the synthesis and characterization of salts containing heterocyclic cations that are paired with two different three-dimensional polyhedral borane/carborane anions, B12H12(2-) and CB11H12(-), as well as a new aqueous preparation method that does not require air-free techniques.