Crystal growth and structure refinement of K4Ge9

Abstract

Deep-red moisture and air sensitive single crystals of K4Geg were obtained by reacting GeO2 and elemental Ge with metallic W and K at high temperature in a niobium ampoule. The crystal structure of the compound was determined by single crystal X-ray diffraction experiments. K 4Ge9 crystallizes in a polar space group R3c (No. 161), Z = 4 with a = 21.208(1) and c = 25.096(2) A. The compound contains discrete Ge94- Wade's nidoclusters which are packed according to a hierarchical atom-to-cluster replacement of the Cr3Si prototype and are separated by K+ cations. Two independent [Ge 9]4- clusters A (at Cr positions) and B (at Si positions) are found with a ratio A:B = 3:1. The B-type cluster satisfactorily represents orientational disorder around the three-fold axis. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.