Acidobasic behavior of the diphosphato dodecameric ring [(HPO4)2Mo12S12O12(OH)12(H2O)2]4-.: Synthesis and characterization of the conjugated form [(HPO4)2Mo12S12O12(OH)14(H2O)2]6-

A novel diphosphato anionic ring, [(HPO4)(2)Mo12S12O12(OH)(14)(H2O)(2)](6-) noted B-[P2Mo12](6-) was characterized by single crystal-X ray diffraction. B-[P2Mo12](6-) formally derives from the acidic parent [(HPO4)2Mo(12)S(12)O(12)(OH)(12)(H2O)(2)](4-) (noted A-[P2Mo12](4-)) by addition of two hydroxo groups in the cavity. The phosphate groups are hydrogen bonded to the inner hydroxo bridges. The H-bonding network within the cavity contributes to the elliptical conformations which differ in the acid and basic conjugated forms. The basic B-[P2Mo12](6-) ring was characterized in solution by P-31 NMR. The three-line spectrum indicates that a chemical equilibrium takes place for giving uncoordinated phosphate and a monophosphate ring, noted [PMo10](n-). IR characterizations are also given. (C) 2003 Elsevier Science B.V. All rights reserved.