Low-melting salts based on a glycolated cobalt bis(dicarbollide) anion

A new series of low-melting quaternary ammonium salts based on a glycolated cobalt bis(dicarbollide) anion structure have been synthesized and characterized, and their spectroscopic and physicochemical properties have been studied. The lowest melting point was obtained for 1-butyl-3-methylimidazolium (～50 °C) followed by 1-butyl-1-methylpiperidinium (～80 °C), 1-butyl-1-methylpyrrolidinium (～95 °C), and 1-butyl-4-methylpyridinium salts (～115 °C). The salts were thermally stable up to 180 °C decomposition of an oligo(ethylene glycol) chain] and contained variable amounts of water. The flexible oligo(ethylene glycol) chains contributed to the waxy state of salts. The solubility of the salts was determined for 76 solvents that are commonly used in organic chemistry. Generally, the solubility increased with the dipole moment and relative polarity of the solvent. Salts exhibited good solubility in ketones and esters; moderate solubility was observed in alcohols, aromates, and chlorinated solvents, and poor solubility was obtained in ethers. The salts were practically insoluble in higher hydrocarbons and water. Salts are dissolved in the form of ion pairs or separated ions, depending on the nature of the solvent.