RELATIONSHIP BETWEEN STRUCTURES AND STABILITIES OF MOLYBDATE COMPLEXES OF ALDITOLS - A POTENTIOMETRIC, C-13 AND MO-95 NMR-STUDY

Dinuclear molybdate complexes of alditols have been studied in aqueous acidic solution by 95Mo and 13C NMR. Their formation constants were determined by potentiometry. In all complexes, the dimolybdate group was chelated by four vicinal hydroxyls. Two types of complexes were characterized by NMR, depending on the erythro or threo configuration of the central diol group. Their structures were precised using literature crystal data. A single asymmetrical complex of the first type was formed by symmetrical erythro ligands (erythritol, galactitol), while the asymmetrical d-arabinitol and D-mannitol formed pairs of isomeric species of this type. Ligands with complexing sites involving a central threo group (DL-threitol, xylitol) were complexed in a symmetrical manner. D-Glucitol formed four complexes as pairs of each type. Rules relating the stabilities of the complexes to the structures of the ligands are presented. © 1990.