Copper-rich Intermetallic Compounds RECu9Cd2(RE = La, Ce, Pr, Nd) with YNi9In2-type Structure

The YNi9In2-type copper-rich compounds RECu9Cd2 (RE = La, Ce, Pr, Nd) were synthesized directly from the elements in sealed niobium ampoules in an induction furnace and were characterized by powder X-ray diffraction. The structure of PrCu9Cd2 was refined from single-crystal Xray diffractometer data: P4/mbm, a = 849.0(3), c = 498.2(3) pm, wR2 = 0.0418, 374 F2 values, 23 variables. The structure has two striking polyhedral motifs: Pr@Cu16Cd4 and Cu2@Cu8Cd4. The packing of these polyhedra describes the whole structure. The copper and cadmium atoms build up a three-dimensional [Cu9Cd2] network with broader ranges of Cu–Cu (246 – 274 pm) and Cu–Cd (272 – 288 pm) distances. The cadmium atoms show segregation through pair formation with Cd–Cd distances of 288 pm.