Abstract
The kinetics of the complexation of the Li/sup +/ ion with ligands cryptand 222 and cryptand 221 (C222 and C221) were studied in acetonitrile, propylene carbonate, and acetone solutions by lithium-7 NMR line-shape analysis. The predominant mechanism of exchange between the solvated and the complexed Li/sup +/ ion sites for the C222-LKlt. slashi/sup +/ system in all solvents is dissociative, while a bimoleuclar mechanism predominates for the C221-Li/sup +/ system in acetonitrile and propylene carbonate solutions. The kinetics parameters for the exchange have been determined. For the dissociative exchange mechanism, there is a correlation between the solvating abilities of the solvents, as expressed by the Gutmann donor numbers, and the dissociation rates as well as the activation parameters of the reaction. In systems where a bimolecular exchange mechanism predominates, the free-energy barrier for the exchange processes appears to be independent of the nature of the solvent.
Published Version
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