Mossbauer-spectroscopic characterization of the stannides Sr₂Pd₂Sn and Eu₂Pd₂Sn

The Ca2Pd2Ge-type stannides Sr2Pd2Sn and Eu2Pd2Sn were synthesized by reaction of the elements in sealed tantalum ampoules in a high-frequency furnace and characterized by powder X-ray diffraction. The structure of Sr2Pd2Sn (Fdd2, a = 1063.95(5), b = 1623.22(9), c = 594.63(14) pm, wR2 = 0.0472, 972 F-2 values and 26 variables) was refined from single-crystal X-ray diffractometer data. The striking structural motif features equidistant chains formed by the palladium atoms (304.7 pm Pd-Pd), which are interlinked by the tin atoms (266.9 and 268.7 pm Pd-Sn). Together, the palladium and tin atoms form a three-dimensional [Pd2Sn]delta(-) Polyanionic network in which the strontium atoms reside in larger cavities. The divalent character of europium in Eu2Pd2Sn was manifested by Eu-151 Mossbauer spectroscopy. The isomer shift is delta = -9.48(1) mm s(-1) at room temperature. The results of Sn-119 Mossbauer-spectroscopic experiments have confirmed the tin site determined by the single-crystal study, the isomer shifts being delta = 1.71(1) mm s(-1) for Eu2Pd2Sn and delta = 1.73(1) mm s(-1) for Sr2Pd2Sn. Sr2Pd2Sn is a Pauli paramagnet with a susceptibility of 2.2(1) x 10(-5) emu mol(-1) at room temperature. Eu2Pd2Sn shows Curie-Weiss paramagnetism with an experimental magnetic moment of 7.85(1) mu(B) per Eu atom, confirming divalent europium. The europium magnetic moments order antiferromagnetically at T-N = 14 K.