Metal-rich phosphides RE5Ir 19P 12 with Sc 5Co 19P 12 type structure

Abstract

The iridium-rich phosphides RE 5Ir 19P 12 ( RE=Sc, Y, La–Nd, Sm–Lu) with Sc 5Co 19P 12 type structure, space group P62̄ 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 RE 5Ir 19P 12 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 ThCr 2Si 2 and SrPtSb related slabs. Striking structural motifs of the RE 5Ir 19P 12 structures are slightly distorted tricapped trigonal prisms of the metal atoms around the phosphorus atoms. The iridium and phosphorus atoms build up three-dimensional [Ir 19P 12] polyanionic networks (230–286 pm Ir–P and 282–296 pm Ir–Ir in La 5Ir 19P 12) which leave cavities of coordination numbers 16 and 15 for the rare earth atoms.