Potassium and Rubidium Oxocadmates
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Abstract The crystal structure of K6[CdO4] and Rb2CdO2 has been determined from single crystal X-ray diffraction data and refined toR=0.058 (K6[CdO4]) andR=0.088 (Rb2CdO2). K6[CdO4] crystallizes hexagonal, space group P63mc with lattice constantsa=867.42 (6),c=665.5 (1) pm,c/a=0.767 andZ=2. It is isotypic with Na6[ZnO4]. Rb2CdO2 is orthorhombic, space group Pbcn witha=1045.0 (2),b=629.1 (1),c=618.3 (1) pm,Z=4, and crystallizes with the K2CdO2 structure type. The crystal structures can be deduced from the motif of a closest packed arrangement of O2− with hexagonal (K6[CdO4]) or cubic (Rb2CdO2) stacking. The tetrahedra occupied by Cd2+ are isolated (K6[CdO4]) or edge-shared (formation of infinite SiS2-like chains [CdO4/2]) (Rb2CdO2). The powder diffraction pattern of Rb6[CdO4] [a=906.6 (1),c=694.3 (1) pm] and Rb2Cd2O3 [a=642.6 (2),b=679.0 (1),c=667.9 (2) pm, β=115.2 (1)] confirm isotypie with K6[CdO4] and K2Cd2O3 respectively.
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