A first example of polyoxotungstate-based giant molecule. Synthesis and molecular structure of a tetrapod-shaped Ti-O-Ti bridged anhydride form of Dawson tri-titanium(IV)-substituted polyoxotungstate

The preparation and structural characterization of a giant tetrapod-shaped inorganic molecule, [(alpha- 1,2,3-P2W15Ti3O60.5)(4)Cl](37-),1a (abbreviated to {TiO6}(12); FW similar to15700), consisting of four tri-Ti-IV-1,2,3-substituted alpha-Dawson substructures and one encapsulated Cl- ion, are described. A water-soluble, all-inorganic composition compound of the tetrameric Ti-O-Ti bridged anhydride form, NaxH33-xK4[1a] .yH(2)O, 1 (x = 21-26, y = 60-70), being afforded by a stoichiometric reaction in aqueous solution of tri-lacunary Dawson polyoxotungstate Na-12[B-alpha-P2W15O56].19H(2)O with 3 equiv of Ti(SO4)(2).4H(2)O in HCl-acidic aqueous solution followed by exchanging the countercation, was obtained as analytically pure, homogeneous colorless plate crystals. Single-crystal X-ray Structure analysis revealed that the polyoxoanion 1a was an inorganic, giant tetrapod-shaped molecule (described as a sphere with a diameter of similar to31.2 Angstrom) with approximately T-d symmetry. Characterization of 1 was also accomplished by complete elemental analysis, TG/DTA, FTIR, UV-vis absorption and solution (P-31 and W-183) NMR spectroscopy.