SOLUTION AND COORDINATION ENTHALPIES (SOLID-STATE) OF LITHIUM AND SODIUM MACROCYCLE (ETHYL P-TERT-BUTYLCALIX(4)ARENE TETRAETHANOATE, CRYPTAND-222 AND CROWN-ETHERS) SYSTEMS

A series of lithium and sodium ethyl p-tert-butylcalix(4)arene tetraet hanoate and cryptand 222 salts has been isolated and thermochemically characterised in acetonitrile at 298.15 K. Also reported are the stand ard enthalpies of solution of common sodium salts (tetrafluoroborate, trifluoromethanesulfonate, iodide and bromide) in this solvent at the same temperature. Solution data for the free and the complexed salts a nd for the ligand are combined with complexation data for the appropri ate cation and macrocycle in acetonitrile to derive the enthalpies of co-ordination of these systems for the process where the product and t he reactants are in the solid state. Comparison of data involving lith ium and the calix(4)arene ester and the cryptand 222 with those for cr own ethers reflects considerable weakening of cation-anion interaction s in the former ligands relative to crown ethers. It is concluded that for a given ligand and metal cation, the anion effect is reflected in the co-ordination enthalpies. On the other hand, for systems containi ng the same ligand and anion, there is a decrease in enthalpic stabili ty in moving from lithium to sodium. The need to obtain experimental d ata on crystal lattice enthalpies of these ligands and their metal ion complex salts is emphasised.