Peroxo complexes of sugar acids with oxoions of MoVI and WVI as studied by NMR spectroscopy

Abstract

By using multinuclear ¹H, ¹³C, ¹⁷O, ⁹⁵Mo and ¹⁸³W magnetic resonance spectroscopy (1-D and 2-D), aldonic acids, alduronic acids and aldaric acids have been found respectively to form one, four and three homologous oxoperoxo complexes with Mo^VI and W^VI, in aqueous solution (pH range 2–11). Common features are the involvement of two peroxide units per metal centre and the co-ordination of the sugar acids through carboxylate and adjacent hydroxyl groups. Accordingly, 1∶1∶2 (metal∶acid∶peroxide) complexes are detected as well as 2∶1∶4 species in the case of the aldaric acids. The geometry around each MO⁴⁺ centre is approximately pentagonal bipyramidal, the MO group occupying one of the apical positions and the two peroxo ligands being equatorial. The sugar acid is co-ordinated in one equatorial and in one apical site.