22-Isopolytungstate Fragment [H₂W₂₂O₇₄]¹⁴⁻Coordinated to Lanthanide Ions

The novel polyanions [Ln2(H2O)10W22O71(OH)2]8− (Ln = La (1), Ce (2), Tb (3), Dy (4), Ho (5), Er (6), Tm (7), Yb (8), Lu (9), Y (10)) have been synthesized by reaction of WO42− and lanthanide ions in acidic aqueous medium. The low symmetry (Ci) polyanion family [Ln2(H2O)10W22O71(OH)2]8− consists of the isopolyanion [H2W22O74]14− and two {Ln(H2O)5}3+ supporting units. The [H2W22O74]14− cluster, which consists of two undecatungstate {W11} fragments, acts as a tridentate ligand to two Ln3+ ions. Polyanions 1−10 are isostructural, and the coordination number of the lanthanide ions correlates with their sizes. All compounds have been fully characterized in the solid state by Fourier transform infrared spectroscopy, single-crystal X-ray diffraction, thermogravimetric analysis, and elemental analysis. Single-crystal X-ray diffraction analyses show that 1−10 crystallize as sodium salts in the triclinic space group P1̅.