Synthesis and thermolysis of sodium–manganese paratungstate Na5[Mn2.5(W12O40(OH)2)]*36H2O

Abstract

A new procedure for the preparation of sodium–manganese paratungstate was developed and used to synthesize Na5[Mn2.5(W12O40(OH)2)]36H2O. This procedure implies an acidity ratio represented as Z=С(H+)/С(WO42–)=1.00 and a component ratio of CW:CMn=6:1, which enables the synthesis of compounds to be faster, more cost-effective, and with lower energy consumption. The composition and single-phase nature of the compound was confirmed by elemental analysis and scanning electron microscopy. Furthermore, the nature of the paratungstate anion within its composition was determined by IR spectroscopy. Thermolysis of synthesized Na5[Mn2.5(W12O40(OH)2)]36H2O was studied, revealing that the dehydratation process proceeds in a full accordance with the entry of water molecules into the coordination spheres of cations and anions. The sequence of H2O removal with increasing temperature is as follows: outer sphere; H2O molecules from the Na coordination environment; H2O molecules from the Mn coordination environment; and constitutional H2O molecule from the anion composition.