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

The novel, dimeric titanium( IV )‐substituted phosphotungstate [(TiP 2 W 15 O 55 OH) 2 ] 14− ( 1 ) has been synthesized and characterized by IR and 31 P NMR spectroscopy, elemental analysis, and single‐crystal Xray diffraction. The polyanion consists of two [P 2 W 15 O 56 ] 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 P 2 W 15 O 56 subunit. The edge‐shared TiO 6 units are symmetrically equivalent and have no terminal ligands. Polyanion 1 shows a chiral distortion within each P 2 W 15 Ti fragment. We also report on the structural characterization of the tetrameric, supramolecular species [{Ti 3 P 2 W 15 O 57.5 (OH) 3 } 4 ] 24− ( 2 ). Polyanion 2 is composed of four equivalent P 2 W 15 Ti 3 fragments, fused together through terminal TiO bonds, leading to a structure with T d symmetry.