| Abstract: | On the Constitution of Peroxotantalates(V) with Alkali Metals: On the Structure of K3[Ta(O2)4] [1] By solving of recently precipitated Ta2O5 · aq in a 1.5-molar solution of KOH in 3% H2O2 and subsequently cooling at 0°C we obtained colourless single-crystals of K3[Ta(O2)4]. The compound crystallizes tetragonal (spacegroup 142m) with a = 679.5(1) pm, c = 791.2(1) pm, Z = 2 (Guinier-de-Wolff powder data). The determinated crystal structure (four-circle diffractometer, 444 out of 444 I0(hkl); R = 1.51%, Rw = 1.48%, parameters see text) proves that K3[Ta(O2)4] is isotypic with K3[Cr(O2)4] [2]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these calculated via Mean Fictive Ionic Radii, as well as charge distribution (CHARDI) are calculated and discussed. |
