One pot-synthesis of the fourth category of dinuclear molybdenum(VI) oxalate series: Structure and study of thermal and redox properties

One pot-synthesis of the fourth category of dinuclear molybdenum(VI) oxalate series. [Display omitted] •One-pot synthesis is a good strategy for obtaining oxalatomolybdate compounds ([Mo2O6(C2O4)2]4−).•The acidity of the medium favors the reduction of the anion [Mo2O6(C2O4)2]4−.•[Mo2O6(C2O4)2]4− is thermally stabilized if isolated with tertiary ammoniums as [HDabco]+. Three new dinuclear molybdenum(VI) oxalate (Pr2NH2)4·[Mo2O6(C2O4)2] (1), (iPr2NH2)4·[Mo2O6(C2O4)2] (2) and (HDabco)4[Mo2O6(C2O4)2]·2H2O (3) compounds, have been prepared by one pot-synthesis at room temperature and characterized by single crystal X-ray diffraction and vibrational spectroscopies. Each compound contains the binuclear [Mo2O6(C2O4)2]4− anion where each molybdenum is in an octahedral MoO6 environment. In compound (3), the interconnection between [Mo2O6(C2O4)2]4− anions, [HDabco]+ cations and water molecules (H2O) leads to an infinite inorganic-organic chain structure. Similarly, in compounds (1) and (2) the interactions between [Mo2O6(C2O4)2]4− anions and respectively [Pr2NH2]+ and [iPr2NH2]+ cations leads to an infinite inorganic-organic chain structure. A remarkable difference between the compounds is that in compounds (1) and (2) interactions between the chains involve only Van der Waals forces giving rise to layer-like structures, which also interact between them only by Van der Waals forces, whereas in compound (3) the chains interact also through hydrogen bonds giving a 3D supramolecular structure. The thermal properties of the compounds were investigated through thermogravimetric and differential thermal analyzes. The differences in the thermal decomposition of the compounds in the solid state are discussed in relation with their crystal structure. Cyclic voltammetry shows that the [Mo2O6(C2O4)2]4− anion can be reduced in both aprotic solvent and water.