BaRu_3Sn_6 – A Tin-rich Stannide with Ba@Sn_8 and Ru@Sn_7 Building Units

摘要

BaRh_3Sn_6 has been prepared by melting of the elements in a sealed tantalum tube and subsequent annealing. It crystallizes in the BaRh_3Pb_6-type structure: Cmcm, a = 807.4(2), b = 2615.3(6), c = 444.0(1) pm, wR = 0.0535, 957 F~2 values, 36 variables. The structure is composed of Ba@Sn_8 trapezoids (349 and 353 pm Ba–Sn) and Ru@Sn_7 units (255–284 pm Ru–Sn) which can be derived from an octahedron by replacement of one apex by a pair of tin atoms. The Ru@Sn_7 units are condensed to strands via the trapezoidal faces, and these strands are connected to the Ba@Sn_8 trapezoids via common edges. The tin substructure of BaRu_3Sn_6 exhibits a broad range of Sn–Sn distances (310 – 354 pm).