Synthesis of Preyssler-Type Phosphotungstate with Sodium Cation in the Central Cavity through Migration of the Ion

Thermal migration of sodium cation in the cavity of Preyssler-type phosphotungstate is reported here. Heating of a Preyssler-type compound, [P5W30O110Na(side)(H2O)]14¹, in which a sodium cation occupies one of the two side cavities, at 300 °C forms a new compound, [P5W30O110Na(center)]14¹, in which the sodium cation is encapsulated in the central cavity. Characterization by single crystal X-ray structure analysis, NMR spectroscopy, elemental analysis, IR, and ESI-MS confirmed the structure of the compound. The thermal displacement ellipsoid of the central sodium, estimated by the crystallographic study, is elongated along the direction perpendicular to the equatorial plane of the Preyssler molecule. These results confirmed prediction using DFT calculation by López and Poblet (ref. 21, J. Am. Chem. Soc. 2007, 129, 12244.) that the most stable site for sodium is the central cavity with a slight shift from the center of the molecule.This research was supported by the Furukawa Foundation for the Promotion of Technology, JSPS KAKENHI Grant Numbers JP18H02058 (Grant-in-aid for scientific research (B)) and JP19K05510 (Grant-in-aid for scientific research (C)), the Center for Functional Nano Oxide at Hiroshima University, and JSPS Core-to-Core program. MNKW thankfully acknowledges the financial support from the Indonesia Endowment Fund for Education (LPDP), Ministry of Finance, Republik Indonesia for PhD scholarship (PRJ-36/LPDP.3/2017)