Synthesis, crystal structure of the ammonium vanadyl oxalatophosphite and its controlled conversion into catalytic vanadyl phosphates

The new vanadyl oxalatophosphite, (NH4)2(VOHPO3)2C2O4 2·9H2O has been prepared hydrothermally and its structure solved by combining single-crystal X-ray diffraction and Solid State NMR. Thermogravimetric studies and variable temperature X-ray diffraction showed the reversible departure of water molecules upon heating. At higher temperature, an adequate redox balance during the thermal decomposition of the material, allows to control the preparation of different catalytically active phases in the vanadyl phosphate system: ω-VOPO4 and (VO)2(P2O7).214