2 LASALOCID SODIUM-SALTS

The structures of two new forms of lasalocid sodium salt, sodium 5S-di methyl-6-oxononyl]-2-hydroxy-3-methylbenzoate (A), Na+.C34H53O8-, and sodium S-dimethyl-6-oxon-onyl]-2-hydroxy-3-methylbenzoate diethyl ethe r solvate (B), Na+ C34H53O8-.C4H10O, are reported. Form A exists as a 'head-to-head' dimer, while form B is a 'head-to-tail' dimer. Sodium i s coordinated to six O atoms from the lasalocid anion in both forms, b ut the coordination spheres differ. Form A contains a bridging carbony l O atom, but, remarkably, the carboxylate group does not coordinate t o the sodium ion. In form B, the carbonyl O atom does not bridge but t here is a direct carboxylatesodium interaction.