Synthesis and Thermal Transformations of Tungsten Phosphate Metallate Complexes with Hexamethylenetetramine

The results of the synthesis and identification of complex compounds of hexamethylenetetramine (CH₂)₆N₄ (HMTA) with tungsten phosphate metallates are presented. The processes and crystalline products of thermal decomposition of compounds with the general formula Cat₅[PW₁₁O₃₉Z(HMTA)]∙nH₂O, where Cat = Na⁺, \({\text{NH}}_{4}^{ + }\) ; Z = Co²⁺, Ni²⁺, Zn²⁺; n = 10–13 have been studied by differential scanning calorimetry, IR spectroscopy, and X-ray powder diffraction. The schemes for their thermolysis have been established. It has been shown that ammonium salts during thermolysis form phases of the composition ZO·0.5P₂O₅·11WO₃ or Z_6/73P_6/73W_66/73O₃ with the structure of phosphotungsten bronze. The decomposition products of sodium salts are a mixture of phases with the structures of sodium tungstates Na₂W₂O₇ and Na₂W₄O₁₃. The research results can be used to predict thermal transformations and the composition of thermolysis products of similar complexes of HMTA and tungsten phosphate metallates of other 3d elements.