Zum Aufbau von PbF4 mit Strukturverfeinerung an SnF4

On the Constitution of PbF₄ with Structure Refinement of SnF₄ Colourless single crystals of SnF₄ have been prepared heating powder samples of SnF₄ in Pt-tubes (500°C, 20 d). Single crystals of PbF₄ could be synthesized by pressure fluorination of «PbF_4-x» and sublimation in autoclaves. The fluorides crystallize isostructural in space group I4/mmm with SnF₄: a = 404.42(4) pm; c = 792.41(9) pm; Z = 2 and PbF₄: a = 425.36(8) pm; c = 806.4(1) pm; Z = 2 (Guinier-de Wolff data, Cu-Kα₁). The parameters Z_F2 of both fluorides were refined from four-circle diffractometer data (Siemens AED 2) with SnF₄: R1 = 1.5%; 1623 I₀(hkl) and PbF₄: R1 = 1.0%; 777 I₀(hkl) (SHELXL-93). The structures correspond to the supposition by Hoppe and Dähne from 1962. The Madelung Part of Lattice and Molecule Energy, MAPLE and MAPME, Mean Fictive Ionic Radii, MEFIR, and Effective Coordination Numbers, ECoN, are calculated.