Preparation and characterization of mixed ammonium salts of Keggin phosphomolybdate

Keggin-type modified ammonium salts of molybdophosporic acid were prepared by partial substituting of the ammonium ions by X (X = SbIII, BiIII or SnII) ions. They were characterised by BET method, XRD, 31P NMR, UV–Vis, Raman, IR spectroscopies and thermal analysis (TG and DTA). It appeared that introducing an element X = Sb or Sn led to partially reduced compound corresponding to the electron exchange occurring between Sb(III) or Sn(II) and Mo(VI) without modification of Keggin structure.