Spectroscopic and structural characterizations of ammonium peroxo–carboxylato molybdate(VI) complexes

New ammonium derivatives of peroxo–carboxylato molybdenum(VI) complexes of general formula (NH4)2[MoO(O2)2(HxL)] · nH2O with L=oxalate (ox), citrate (cit), tartrate (tart), glycolate (glyc) and malate (mal) and (NH4)2[MoO2(O2)(L)] with L=oxalate (ox) have been prepared and characterized on the basis of elemental and thermal analysis as well as by IR and 13C NMR spectroscopy. These last two spectroscopic methods have been used to suggest the coordination mode of the ligand in the complexes. The X-ray crystal structures of the compounds (NH4)2[Mo2O2(O2)2(OH)2(ox)2], (NH4)2[MoO(O2)2(ox)] and (NH4)2[MoO(O2)2(glyc)] · 0.5EtOH have been determined, all showing a sevenfold-coordinated Mo atom with bidentate peroxides and carboxylate ligands.