Three sandglass-type molybdophosphates obtained via a new route: Synthesis and characterization of X7[PMo 8O 30] ( X=Na +, K +, NH 4+)

Abstract

Three new polyoxometalates X 7[PMo 8O 30] ( X=Na +, 1; K +, 2; NH 4 +, 3) have been synthesized with the classical Keggin and/or Dawson heteropolymolybdophosphates and PCl 5 in acetonitrile-water solutions via hydrothermal treatment. The three compounds were characterized by different analyses including IR, 31P NMR spectroscopy, elemental analysis, electrochemistry, thermogravimetric analysis (TGA) and powder X-ray diffraction (XRD). Single crystal X-ray analyses were carried out on Na 7[PMo 8O 30] (1) and (NH 4) 7[PMo 8O 30] (3). Compound 1 and 3 crystallize in the orthorhombic system. The structure of compound 2 was confirmed by the IR spectra and powder XRD. All the three compounds contain the same octamolybdophosphate polyoxoanion [PMo 8O 30] 7−, which consists of two Mo 4O 15 moieties linked by one central PO 4 tetrahedron, leading to a remarkable sandglass-like structure.