Gd ₅ Rh ₁₉ Sb ₁₂ − a metal-rich antimonide with a Sc ₅ Co ₁₉ P ₁₂ related structure

Abstract The metal-rich antimonide Gd 5 Rh 19 Sb 12 was synthesized by induction-melting of the elements in a sealed tantalum ampoule. The Gd 5 Rh 19 Sb 12 structure was refined from single crystal X-ray diffractometer data of a twinned crystal: P 31 m , a = 1,349.3(3), c = 417.99(12) pm, w R 2 = 0.0682, 1545 F 2 values and 67 variables. Gd 5 Rh 19 Sb 12 is closely related to the Sc 5 Co 19 P 12 -type. A split position of Rh5 is avoided by a translationengleiche symmetry reduction of index 2 from P <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mrow> <m:mover> <m:mn>6</m:mn> <m:mo>‾</m:mo> </m:mover> </m:mrow> </m:math> $\overline{6}$ 2 m to P 31 m , leading to a fully ordered model. The crucial difference between Sc 5 Co 19 P 12 and Gd 5 Rh 19 Sb 12 concerns the position of the transition metal atoms on the c axis. The Co4 atoms show a split position around the origin in Sc 5 Co 19 P 12 (Co4@Sc 6 trigonal prisms) while the Rh5 atoms in Gd 5 Rh 19 Sb 12 are shifted by c /2 and then form Rh5@Sb 6 trigonal prisms. The remaining substructures of Sc 5 Co 19 P 12 and Gd 5 Rh 19 Sb 12 are comparable. The Rh–Sb and Rh–Rh distances within the [Rh 19 Sb 12 ] substructure range from 255–290 and 292–336 pm, respectively.