Synthesis and crystal structures of antimonides of rare-earth metals and palladium

The new compounds Pr3Pd6Sb5 (a = 13.442(3), b = 4.442(1), c = 9.994(2) Å), Nd3Pd 6Sb5 (a = 13.412(3), b = 4.431(1), c = 9.962(2) Å), and Gd3Pd6Sb5 (a = 13.293(2), b = 4.397(1), c = 9.881(2) Å) are isotypic and crystallize with the Ce3Pd 6Sb5 type structure (Pmmn; Z = 2). The rare-earth metal atoms are arranged in form of three pseudo-body-centered subcells, whereas Pd and Sb atoms form a three-dimensional arrangement derived from the well-known ThCr2Si2 and CaBe2Ge2 structures. GdPdSb (a = 4.566(1), c = 7.444(1) Å) and DyPdSb (a = 4.545(1), c = 7.354(1) Å) crystallize with an ordered variant of the CaIn2 type structure (P63mc; Z = 2), also called as LiGaGe type, with slightly puckered hexagon nets of Pd and Sb atoms, which trigonally coordinate each other. In this series a decreasing radius of the rare-earth metal allows a tetrahedral non-metal environment of the Pd atoms and accordingly ScPdSb (a = 6.310(1) Å) forms the MgAgAs type structure (F43m; Z = 4), a filled variant of the sphalerite type. The antimonides were prepared by heating mixtures of the elements at 600 °C and subsequent annealing at 900 - 1100 °C. Their structures have been determined by single-crystal X-ray methods. © 2006 Verlag der Zeitschrift für Naturforschung.