Rare Earth-rich Cadmium Compounds RE23T7Cd4 (T = Co, Ni, Ru, Rh, Ir, Pt)

Abstract

The rare earth-rich intermetallic compounds RE23T7CD4(RE = La-Nd, Sm, Gd, Tb; T = Co, Ni, Ru, Rh, Ir, Pt) were synthesized by melting of the elements in sealed tantalum tubes in a high frequency furnace. They crystallize with the Pr23Ir7Mg4-type structure, space group P63mc, Z = 2. The structures of La23Pt7Cd4 (a = 1025.4(2), c = 2319.5(5) pm, wR2 = 0.0425, 2587 F2, 74 variables), La23Ru6.87(1)Cd4 (a = 1015.0(2), c = 2282.8(4) pm, wR2 = 0.0383, 2459 F2, 75 variables), and Nd23Rh7Cd4 (a = 990.0(2), c = 2239.0(5) pm, wR2 = 0.0507, 2350 F2, 74 variables) were refined from single crystal X-ray diffractometer data. Central structural motifs of the RE23 T7Cd4 compounds are transition metal-centered trigonal prisms of rare earth atoms and Cd4 tetrahedra. The RE6T prisms are condensed via common edges and corners, leading to three-dimensional networks. Typical interatomic distances in the prismatic network and in the Cd4 tetrahedra are 295 - 313 pm La-Pt and 319 - 325 pm Cd-Cd, respectively (examplarily for La23Pt7Cd4)