Synthesis and crystal structures of Nd6Pt13In22, Sm6Pt12.30In22.70, and Gd6Pt12.48In22.52

The rare earth-platinum-indides Nd6Pt13In22, Sm6Pt12.30In22.70, and Gd6Pt12.48In22.52 were synthesized from the elements by arc-melting of the components. Single crystals were grown using special annealing sequences. The three indides were investigated by X-ray powder and single crystal diffraction: Tb6Pt12In23 type, C2/m, image, image, image, image, image, wR2=0.0629, 3645 F2 values, 126 variables for Nd6Pt13In22, image, image, image, image, wR2=0.0543, 3679 F2 values, 127 variables for Sm6Pt12.30In22.70, and image, image, image, image, wR2=0.0778, 3938 F2 values, 127 variables for Gd6Pt12.48In22.52. Most platinum atoms in these structures have a distorted trigonal prismatic coordination by rare earth metal and indium atoms. Together, the platinum and indium atoms build up a complex three-dimensional [Pt12+xIn23−x] polyanionic network in which the rare earth metal atoms fill distorted pentagonal and hexagonal channels. The 2c Wyckoff site in these structures plays a peculiar role. This site is occupied by indium in the prototype Tb6Pt12In23, while platinum atoms fill the 2c site in Nd6Pt13In22, leading to a linear Pt3 chain with Pt–Pt distances of 275 pm. The crystals with samarium and gadolinium as rare earth metal component show mixed Pt/In occupancies.