Metal-rich phosphides RE5Ir19P12 with Sc5Co19P12 type structure

The iridium-rich phosphides RE₅Ir₁₉P₁₂ (RE=Sc, Y, La–Nd, Sm–Lu) with Sc₅Co₁₉P₁₂ type structure, space group P62?m were synthesized by solid state reactions of the elements in tantalum crucibles. Well shaped single crystals were obtained in bismuth fluxes. All phosphides were characterized on the basis of X-ray powder data. The structures of RE₅Ir₁₉P₁₂ with RE=Sc, La, Ce, Dy, Er, Tm, and Yb were refined from single crystal diffractometer data. The complex structure of these phosphides can be described by an intergrowth of simpler ThCr₂Si₂ and SrPtSb related slabs. Striking structural motifs of the RE₅Ir₁₉P₁₂ structures are slightly distorted tricapped trigonal prisms of the metal atoms around the phosphorus atoms. The iridium and phosphorus atoms build up three-dimensional [Ir₁₉P₁₂] polyanionic networks (230–286 pm Ir–P and 282–296 pm Ir–Ir in La₅Ir₁₉P₁₂) which leave cavities of coordination numbers 16 and 15 for the rare earth atoms.