Zr ₅ Pd ₉ P ₇ -type platinides Nd ₅ Sn ₉ Pt ₇ and Gd ₅ Sn ₉ Pt ₇ − intergrowth structures with ZrNiAl-and TiNiSi-related slabs

The platinides Nd 5 Sn 9 Pt 7 and Gd 5 Sn 9 Pt 7 were synthesized by arc-melting of the elements and subsequent annealing. Nd 5 Sn 9 Pt 7 ( a = 437.43(6) pm, b = 2872.2(4) pm, c = 727.8(1) pm) and Gd 5 Sn 9 Pt 7 ( a = 428.37(8) pm, b = 2869.7(5) pm, c = 720.4(1) pm) crystallize with the non-centrosymmetric Zr 5 Pd 9 P 7 -type structure, orthorhombic space group Amm 2. The structure of the gadolinium compound was refined from single-crystal X-ray diffractometer data. Refinements of the occupancy parameters revealed the formation of tiny defects on four Wyckoff sites, leading to composition Gd 4.95(1) Sn 8.94(1) Pt 6.89(2) for the studied crystal. The tin and platinum atoms build up a three-dimensional [Sn 9 Pt 7 ] δ − polyanionic network with pronounced Sn–Pt bonding (264–289 pm). The Sn3 atoms show formation of a Sn3–Sn3 dumb-bell with a distance of 320 pm. The three crystallographically independent gadolinium atoms are located within distorted pentagonal prismatic channels. They are coordinated by the platinum and tin atoms: Gd1@Pt 6 Sn 8 , Gd2@Pt 5 Sn 8 and Gd3@Pt 5 Sn 8 . Temperature-dependent magnetic susceptibility studies show Curie-Weiss paramagnetism for Gd 5 Sn 9 Pt 7 and an experimental magnetic moment of 8.12(1) µ B per Gd atom, compatible with stable trivalent gadolinium. Gd 5 Sn 9 Pt 7 is ordered antiferromagnetically below a Néel temperature of T N = 15.6(1) K.