A mixed valent Keggin polyoxometallate involving molybdenum and tungsten

A new mixed valent “Mo-W” polyoxometallate K6Mo3W9PO40. 13H2O has been synthesized in the form of single crystals. The structure determination of this cubic phase (a=21.381 Å) shows that it is isotypic to K5.5Na1.5PW10Cu2(H2O)2O38. 13H2O The two structures differ by the nature of the ligands that form the Keggin units “PMo3W9O40” and “PW10Cu2(H2O)2O38” respectively and by the stoichiometry and distribution of the alcaline cations located outside the Keggin units.