The stannide SrPd_2.23Sn_1.73 with CaBe₂Ge₂-type structure

Abstract

SrPd2Sn2 was synthesized by a reaction of the elements in a sealed tantalum tube in an induction furnace followed by annealing in a muffle furnace to increase crystallinity. The polycrystalline sample was studied by powder X-ray diffraction: P4/nmm, a = 464.00(7), c = 1,058.4(4) pm and V = 0.2279 nm3. The CaBe2Ge2-type structure was refined from single-crystal X-ray diffractometer data: a = 464.09(4), c = 1,059.64(8) pm, wR = 0.0507, 307 F 2 values and 17 variables. The single crystal shows small defects (95.9(5) %) on the Pd2 site and 73(5) % Sn2/27 % Pd3 mixing on one 2c site. The refined composition of the single crystal is SrPd2.23Sn1.73. The palladium and tin atoms form a three-dimensional, covalently bonded [Pd2.23Sn1.73] network with short Pd–Sn distances (263.3–271.4 pm). The two crystallographically independent palladium atoms in the network have tetrahedral and square pyramidal tin coordination, respectively. Within the [Pd2.23Sn1.73] network the strontium atoms fill larger cavities. The strontium atoms are coordinated by nine palladium and nine tin atoms.