Temperature and Concentration Dependence of Conductivities of Some New Semichelatoborates in Acetonitrile and Comparison with Other Borates

Abstract

Data on the temperature and concentration dependence of conductivities of some new ionic liquids based on the reduced symmetry of the semichelato-borate anion are presented and compared to data for the corresponding symmetrical chelato-borate and tetrafluoroborate salts. The compounds under investigation are the semichelato-borates tetraethylammonium difluoromono[1,2-oxalato(2-)-O,O′]borate ([TEA][BF2OX]) and the new 1-ethyl-3-methylimidazolium difluoromono[1,2-oxalato(2-)-O,O′]borate ([EMIM][BF2OX]), the chelato-borates tetraethylammonium bis[1,2-oxalato(2-)-O,O′]borate ([TEA][B(OX)2]) and the new 1-ethyl-3-methylimidazolium bis[1,2-oxalato(2-)-O,O′]borate ([EMIM][B(OX)2]), and the well-known tetrafluoroborates tetraethylammonium tetrafluoroborate ([TEA][BF4]) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]). The concentration dependence of conductivities of [TEA][BF2OX], [EMIM][BF2OX], [TEA][B(OX)2], [EMIM][B(OX)2], [TEA][BF4], and [EMIM][BF4] in pure acetonitrile was measured at 25 °C, 5 °C, –15 °C, and –35 °C and fitted to the Casteel−Amis equation. Data presented in this work should clarify the influence of reduced symmetry caused by the substitution of two fluorine atoms by the oxalate moiety in the borate anion on its conductivity behavior, especially at low temperatures.