One-step synthesis of a Keggin-type manganese(II)-substituted phosphotungstate: structural and spectroscopic characterization and non-solvent liquid phase oxidation of styrene

The Keggin-type Cs salt of a mono Mn(II)-substituted phosphotungstate (Cs₅PMnW₁₁O₃₉]) was synthesized from H₃PW₁₂O₄₀, MnCl₂ and CsCl. The complex was characterized in solution as well as in the solid state by spectroscopic, magnetic and electrochemical techniques. The complex crystallized in tetragonal phase. X-ray structural analysis shows two types of disorder in which the Mn and W atoms are distributed over the 12 positions, and the Mn atom could not be distinguished from the 11 W atoms distributed equally over the 12 addenda atoms in the Keggin structure. The catalytic activity of the complex was evaluated for non-aqueous oxidation of styrene using molecular oxygen. The complex gave >99.0% selectivity towards benzaldehyde and could be reused.