Gd3Pt4In12 and Tb3Pt4In12 — New Ternary Indides with Condensed Distorted [PtIn6] Trigonal Prisms

The ternary indium compounds Gd₃Pt₄In₁₂ and Tb₃Pt₄In₁₂ were synthesized from an indium flux. Arc‐melted precursor alloys with the starting compositions ∼GdPtIn₄ and ∼TbPtIn₄ were annealed with a slight excess of indium at 1200 K followed by slow cooling (5 K/h) to 870 K. Both compounds were investigated by X‐ray powder diffraction: a = 990.5(1), c = 1529.5(3) pm for Gd₃Pt₄In₁₂ and a = 988.65(9), c = 1524.0(1) pm for Tb₃Pt₄In₁₂. The structure of the gadolinium compound was solved and refined from single crystal X‐ray data: P3¯m1, wR2 = 0.0470, 1469 F² values and 62 variable parameters. Both crystallographically different platinum sites have a slightly distorted trigonal prismatic indium coordination. These [PtIn₆] prisms are condensed via common edges and corners forming a complex three‐dimensional [Pt₁₂In₃₂] network. The gadolinium, In1 and In7 atoms fill cavities within this polyanion. Tb₃Pt₄In₁₂ is isotypic with the gadolinium compound.