Supramolecular Structures of Titanium(IV)‐Substituted Wells–Dawson Polyoxotungstates

The novel, dimeric titanium(IV )‐substituted phosphotungstate [(TiP₂W₁₅O₅₅OH)₂]^14? ( 1 ) has been synthesized and characterized by IR and ³¹P NMR spectroscopy, elemental analysis, and single‐crystal Xray diffraction. The polyanion consists of two [P₂W₁₅O₅₆]^12? Wells–Dawson moieties linked through two titanium(IV ) centers. Polyanion 1 is a dilacunary species and represents the first Ti‐containing sandwich‐type structure. The titanium centers are octahedrally coordinated by three oxygen atoms of each P₂W₁₅O₅₆ subunit. The edge‐shared TiO₆ units are symmetrically equivalent and have no terminal ligands. Polyanion 1 shows a chiral distortion within each P₂W₁₅Ti fragment. We also report on the structural characterization of the tetrameric, supramolecular species [{Ti₃P₂W₁₅O_57.5(OH)₃}₄]^24? ( 2 ). Polyanion 2 is composed of four equivalent P₂W₁₅Ti₃ fragments, fused together through terminal Ti? O bonds, leading to a structure with T_d symmetry.