Abstract
Solns. of sodium trifluoromethanesulfonate, magnesium trifluoromethanesulfonate, and barium perchlorate in N,N-dimethylformamide (DMF) were investigated using broadband dielec. relaxation spectroscopy at 25 °C. All spectra were dominated by a solvent relaxation process centered at ∼15 GHz but also exhibited one (for NaCF3SO3) or two (for the 2:1 salts) low-amplitude processes, centered at ...
Abstract
Solns. of sodium trifluoromethanesulfonate, magnesium trifluoromethanesulfonate, and barium perchlorate in N,N-dimethylformamide (DMF) were investigated using broadband dielec. relaxation spectroscopy at 25 °C. All spectra were dominated by a solvent relaxation process centered at ∼15 GHz but also exhibited one (for NaCF3SO3) or two (for the 2:1 salts) low-amplitude processes, centered at frequencies below 2 GHz, that could be attributed to the presence of ion pairs. Effective solvation nos. calcd. from the solvent relaxation amplitudes indicated strong solvation of all three cations, with evidence for the formation of a second solvation sheath for Mg2+ and possibly Ba2+. Detailed anal. of the solute-related processes showed that solvent-shared ion pairs (SIPs) were formed in NaCF3SO3 solns. in DMF. The data for Mg(CF3SO3)2 and Ba(ClO4)2 solns. were not definitive but, consistent with the solvation evidence, favored the presence of double solvent-sepd. ion pairs and SIPs. Overall assocn. consts., KA, were small for all three salts in DMF and increased in the order: NaCF3SO3 < Ba(ClO4)2 < Mg(CF3SO3)2.
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