Equiatomic Rare Earth (Ln) Transition Metal Antimonides LnTSb (T=Rh, lr) and Bismuthides LnTBi (T=Rh, Ni, Pd, Pt)

Thirty-eight new ternary equiatomic antimonides and bismuthides were prepared by reaction of the elemental components at high temperatures, and the structures of four compounds were refined from single-crystal X-ray data. The antimonides LnRhSb (Ln=Sm, Gd-Tm) and LnIrSb (Ln=La-Nd, Sm, Gd-Tm) crystallize with the orthorhombic TiNiSi-type structure, which was refined for TbRhSb (a=713.3(2) pm, b=452.0(1) pm, c= 778.8(2) pm, R=0.016 for 306 structure factors and 20 variable parameters) and SmIrSb (a= 722.4(2) pm, b=452.9(1) pm, c=786.1(2) pm, R=0.023 for 559 F values and 20 variables). The bismuthides LnRhBi (Ln=Pr-Sm) also crystallize with TiNiSi-type structure which was refined for SmRhBi (a=728.0(2) pm, b=467.9(1) pm, c=795.7(2) pm, R=0.037 for 481 F values and 20 variables). The hexagonal ZrNiAl-type structure was established for the compounds LnRhBi (Ln=Gd-Er) through a structure refinement of DyRhBi (a=757.9(2) pm, c=392.6(1) pm, R=0.026 for 423 F values and 14 variables). The bismuthides LnNiBi (Ln=Pr, Nd, Sm, Tb, Ho, Er), ScPdBi, LnPdBi (Ln=La, Er, Tm, Lu), and LaPtBi are isotypic with cubic MgAgAs. The atomic order for these equiatomic ternary bismuthides was determined for PrNiBi and LaPtBi from X-ray powder data. The structural chemistry of these compounds is briefly discussed.