A MULTINUCLEAR NMR-SPECTROSCOPY CHARACTERIZATION OF DINUCLEAR TUNGSTEN(VI) COMPLEXES OF TRIDENTATE AND PENTADENTATE MESO-D-GLYCERO-D-GULO-HEPTITOL AND D-GLYCERO-L-GULO-HEPTITOL

The formation of W(VI) complexes of two C-6 epimeric heptitols, namely meso-D-glycero-D-gulo-heptitol and D-glycero-L-gulo-heptitol, has bee n studied in aqueous solution. In alkaline medium, both heptitols form two types of dinuclear complexes which have been structurally charact erized from multinuclear NMR data. In the first type T, the site of ch elation is a tridentate xylo system. In the second type P, the site of chelation is a pentadentate system with a central;xylo triol group. T he influence of the nature and orientation of the substituents attache d to the lateral carbon atoms of the chelating site upon the complex s tability is discussed. (C) 1998 Elsevier Science Ltd. All rights reser ved.