Solid‐State Ion Migration in the Preyssler‐Type Phosphotungstate for the Preparation of the Dipotassium Cation‐Encapsulated Derivative

The heat-driven solid-state transformations of K salts of the Na-encapsulated Preyssler-type phosphotungstates, K14[P5W30O110Na(side)(H2O)] and K14[P5W30O110Na(center)], are reported herein. K14[P5W30O110Na(side)(H2O)] contains one Na+ in one of the side cavities and a coordinating H2O molecule while K14[P5W30O110Na(center)] contains one Na+ in the central cavity. The heating of K14[P5W30O110Na(side)(H2O)] produces [P5W30O110Na(center)]14–, [P5W30O110K(center)]14–, and [P5W30O110K(side)2]13–. [P5W30O110K(center)]14– and [P5W30O110K(side)2]13– contain mono-K+ in the central cavity and di-K+ in both side cavities, respectively. The heating of potassium salt of [P5W30O110Na(center)]14– produces [P5W30O110K(center)]14– and [P5W30O110K(side)2]13–. These results indicate that heating, at 200–500 °C, causes the migrations of Na+ and K+, without the collapse of the molecule. K14[P5W30O110Na(side)(H2O)] was successfully converted to 12Na[P5W30O110K(side)2] by repeated solid-state heating, which was periodically interrupted by dissolution, in H2O, and drying.