Caesium solvation

If the proposed structure was true, then a solvent of higher solvating power, such as dme, should decrease the stability of the intramolecular complex. Using sodium as the counterion part of the active centres should exist in the form of externally solvated contact ion pairs or even solvent-separated ion pairs. With caesium as the counterion there should be little change, because this cation is only poorly solvated by both solvents and consequently the possibility of solvent-separated ion pairs to be found should be extremely small. 

The two extrathermodynamic assumptions used in Table 9 to derive solvent activity coefficients of anions, lead to different values of y cicHsi-)+ The assumption (i) that caesium cation is similarly solvated in methanol and in DMF, suggests that the large rate difference between reaction (27) in methanol and in DMF is as much due to differences in transition state solvation as to differences in solvation of chloride ion. This is the situation shown qualitatively in Fig. 1. On the other hand, the somewhat smaller rate difference between reaction (27) in formamide and in DMF is due entirely to differences in solvation of chloride ion, if the caesium assumption is applied to formamide and to DMF. 

The caesium assumption is popular with electrochemists and gives results comparable with the ferrocene-ferricinium assumption (ii) at least for solutions in water, formamide, methanol, and acetonitrile (Kolthoff, 1964 Strehlow, 1952 Koepp et al., 1960). However, we favour the tetraphenylarsonium-tetraphenylboride assumption of Grunwald et al. (1960) because it makes a more satisfactory allowance for size effects, such as making and breaking of solvent structure, while still preserving the attractive features, as to electrostatic solvation, possessed by the ferrocene-ferricinium couple and the caesium cation. 

With fluorenyl caesium (FICs) in dimethoxymethane, addition of tetrahydro-furan appears to generate triple ions, Fl2Cs and FICs2, in equilibrium with ion pairs which are only weakly dissociated into free ions. The derived thermodynamic data indicate that dimethoxymethane, although having a lower dielectric constant than tetrahydrofuran, specifically solvates Cs". ... 

Using pulse radiolysis, Dye et al. [99] have studied the formation of Na" from and sodium in ethylenediamine. The reaction of caesium with water in ethylenediamine again shows that the solvated electron reaction with water is slow [95, 100]. 

The Raman spectrum of a solution of BiFg in hydrogen fluoride shows lines due to the pentafluoride only, indicating that it is a weaker Lewis acid than SbFg, but on addition of caesium fluoride, CsBiFg could be obtained as a solvate with 2—3 moles of HF. The Raman spectrum was assigned on the basis of octahedral symmetry. 

Ethanol has also received considerable attention as a solvent over a long period of time. Data on this solvent, however, are rather few compared to methanol and very few systematic studies exist. Several solubility studies have been made since the publication of Seidell and Linke. Thomas has reported solubilities for the alkali metal iodides at 20 and 25°C, and observed a decrease in solubility with an increase in ionic radius of the cation. Deno and Berkheimer have reported the solubilities of several tetraalkylammonium perchlorates. In every case the solid phase was the pure salt. Solubilities for several rare earth compounds have been reported.Since all of these salts form solvates in the solid phase, the results cannot be used in thermodynamic calculations without the corresponding thermodynamic values for the solid phases. Solubilities of silver chloride, caesium chloride, silver benzoate, silver salicylate and caesium nitrate have been measured in ethanol, using radioactive tracer techniques. Burgaud has measured the solubility of LiCl from 10.2 to 57.6°C and observed that there is a transition from the four-solvated solid phase to the non-solvated phase at 20.4°C. 

CafiHi2CS2N12f Caesium tetracyanoguinodimethanide, 29, 650 31B, 43 C38H34OS, Obtusaguinone dimer benzene solvate, 42B, 9l... 

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