Crystal structure of Rb2[Ti(VO2)3(PO4)3]

The crystal structure of the new compound Rb2[Ti(VO2)3(PO4)3] obtained by hydrothermal synthesis in the RbCl-TiPO4-V2O5-B2O3-H2O system (a = 13.604(2) Å, c = 9.386(2) Å, sp. gr. P6cc, Z = 4, ρcalcd = 3.32 g/cm3) has been studied by X-ray diffraction (Xcalibur-S-CCD diffractometer, R = 0.038). It is shown that the isotypism of Rb2[Ti(VO2)3(PO4)3] and Cs2[Ti(VO2)3(PO4)3] is caused by the flexibility of a mixed anionic framework composed of phosphorus tetrahedra, vanadium five-vertex polyhedra, and titanium octahedra (bases of the crystal structures of these compounds). The topological correlations between the structures of titanium-vanadyl phosphates and benitoite and beryl silicates are analyzed.