Density, viscosity, and dielectric constant of dimethoxyethane (DME) and tetrahydrofuran (THF) were investigated in the temperature range +25 to -700 and found to be remarkably similar for both solvents. Conductance of tetraphenylboride salts of Nar, C+, and Bu(Am)'iN+ were investigated in both media, down to 5 X 10~6 M concentration and over the whole temperature range of +25 to -70°. The respective 0+, Á+,, and -AHdia showed that Bu(Am)¡N+,BPhr forms contact ion pairs in both solvents and dissociates into free Bu-( )% + and BPhr ions not coordinated with solvent. The simple "sphere in continuum" model accounts for the quantitative behavior of this salt in DME and THF. However, to account for the behavior of Na+,BPhr, it is necessary to assume that in both media the salt forms mainly solvent-separated pairs which dissociate into solvent-coordinated Na+ ions. While the behavior of Bu(Am)¡N+ ,BPhf or Nad,BPhr is similar in THF and DME, that of Cs^,BPhr is different in DME from that in THF. It was shown that the medium-size, free Cs+ ion is coordinated with DME but not with THF, whereas the Cs+,BPhr forms mainly contact ion pairs in both solvents. Therefore, the "sphere in continuum" model ( ) were determined for a temperature range of -70 up to +25°. In addition, the conductance of Na+, Cs+, and (z-Am)sBuN+ (z'-Am = isoamyl) salts of BPh4" was investigated in the same temperature range.

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Formation constants, K , and single ion conductances, A,, of complexes of Na+ and K+ with a series of 4'-substituted monobenzo-15-crown-5 and monobenzol8-crown-6 ligands were determined conductometrically in acetone at 25 OC. For the complexes of Na+ with benzo-15-crown-5 ligands a 25-fold difference in K is observed between the 4'-amino and 4'-nitro derivative. A good Hammett correlation is found by plotting log K vs. up-+ u, for nine 4'-derivatives, the p value being -0.45. The substituent effect in Na+/benzo-l8-crown-6 complexes is much smaller, and almost negligible for electron withdrawing substituents. No Hammet correlation is found. It is argued that in this system the pronounced difference in the diameters of cation and crown cavity causes the distance between the cation and the aromatic oxygen atoms to change as a function of the nature of the substituent, which in turn can induce conformational changes in the polyether ring. Substituent effects are somewhat larger for K+/benzo-18-crown-6 complexes, but again no linear Hammett plot is obtained. In mixtures of K+ with monobenzo-15-crown-5, 1:l and 2:l crown-cation complexes can exist simultaneously, and, although no K values could be calculated, substituent effects on the complexation are quite pronounced.

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