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 degrees C, 20 d). Single crystals of PbF4 could be synthesized by pressure fluorination of 'PbF4-x' and sublimation in autoclaves. The fluorides crystallize isosructural 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-K alpha(1)). The parameters z(F2) of both fluorides were refined from four-circle diffractometer data (Siemens AED 2) with SnF4: R1 = 1.5%; 1623 I-o(hkl) and PbF4: R1=1.0%; 777 I-o(hkl) (SHELXL-93). The structures correspond to the supposition by Hoppe and Dahne 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.