Complex formation in Nb6O 19 8− -WO 4 2− -H+-H2O system where c Nb: c W = 4 : 2

Abstract

Processes occurring in Nb6O198−-WO42−-H+-H2O system where cNb: cW = 4: 2, cNb+W0 = 5 × 10−3, 2.5 × 10−3, or 10−3 mol/L, and ionic strengths I = 0.01–0.14 are created by NaCl background electrolyte were studied by pH titration and mathematical modeling. Solute ion species distribution diagrams were obtained for \( Z = \frac{{c_{H^ + }^0 }} {{c_{Nb + W}^0 }} = 0 - 1.5 \). The concentration constants and thermodynamic constants of formation were calculated for isopolyniobotungstate anions (IPNTAs). HxNb4W2O19(6−x)−, (x = 1–5), ions were shown to appear in solution only after Nb6O198− was protonated and aquapolytungstate anions were formed. The results of modeling were supported by the synthesis of Tl3H3Nb4W2O19 · 16.5H2O, Tl2H4Nb4W2O19 · 11H2O, and NaTl3(H4Nb4W2O19)2 · 22H2O salts, which were identified by chemical analysis and IR spectroscopy.