Ce2Ru2In3 and Ce3Ru2In2: Site exchange in ternary indides of a new structure type

Cerium ruthenium indides, Ce2Ru2In3 and Ce3Ru2In2, were synthesized from the pure elements by arc-melting. Both structures present a site exchange variant of a new structure type with different occupation of one crystallographic site: space group Pnma, Z = 4, oP28, with cell parameters a = 17.7054(4) A, b = 4.7144(1) A, c = 7.4072(1) A for Ce2Ru2In3, and a = 17.394(2) A, b = 4.9073(6) A, c = 7.669(1) A for Ce3Ru2In2 at room temperature. In the structures there are eight extremely short Ce–Ru contacts per unit cell: Ce1–Ru1 = 2.3225(8) A, Ce1–Ru2 = 2.3681(8) A in Ce2Ru2In3, and Ce1–Ru1 = 2.2345(9) A, Ce3–Ru2 = 2.2811(9) A in Ce3Ru2In2. Such contacts cause considerable distortion of coordination polyhedra of all atoms and reduce cell parameter a by 1 A when compared to the parent NdRh2Sn4 structure.