183W NMR and X-Ray Crystallographic Studies on the Peroxo Complexes of the Ti-Substituted α-Keggin Typed Tungstophosphates

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Abstract
Peroxo complexes prepared by the reaction of titanoundecatungstophosphate (PTiW11O405−) and dititanodecatungstophosphate (PTi2W10O407−) with hydrogen peroxide are characterized by means of the 183W NMR spectroscopy and the single crystal X-ray diffractometry. Electronic spectra and permanganate titration analyses indicated that one peroxo ligand attaches to the PTiW11O405− anion and two peroxo ligands attach to the PTi2W10O407− anion. 183W NMR spectra showed that the Cs symmetry of the PTiW11O405− anion and the C2 symmetry of the PTi2W10O407− anion are retained in the respective peroxo derivatives. Single crystal X-ray structures of the diisopropyl ammonium salt of PTiW11O405−, the diisopropyl ammonium salt of PTiW11O39(O2)5− and the isopropyl ammonium salt of PTi2W10O38(O2)27− indicated that the peroxo anions retain the α-Keggin structures of their parent anions. It was inferred that the peroxo ligands are substituted for the terminal oxygen atom at the TiO6 octahedra with the side-on format.