Crystal structure of potassium and ammonium tetraperoxovanadates (V)

Abstract

Powder diffraction measurements are fast, and sample preparation does not require time consuming manipulations what is very important for toxic, unstable or explosive samples. In addition, very good results can be also obtained at structure solution level by nowadays methods. Unfortunately, structure solution results can sometimes be biased towards assumed structure models in most popular nowadays ‘direct space search procedures’. However, in typical applications crystal structure studies can be performed using ‘ab initio’ methods. Using this approach the crystal structures of two very unstable tetraperoxovanadates (V) — (NH4)3[V(O2)4] and K3[V(O2)4] — have been ab initio solved from powder diffraction data by direct methods. The two ammonium and potassium salts are isotypic with lattice parameters: a = 6.9769(5), c = 8.211(1) and a = 6.6861(4), c = 7.708(2) Å, V = 399.68(7) Å3 and 344.6(6) Å3, respectively. The space group is I-42m (No. 121) with Z = 2 for both compounds.