| Abstract
| - The new stannide ScAgSn was synthesized by induction melting of the elements in a sealed tantalum tube andsubsequent annealing. ScAgSn crystallizes with a pronounced subcell structure: ZrNiAl type, P6̄2m, a = 708.2(2)pm, c = 433.9(1) pm, wR2 = 0.1264, 321 F2 values, and 14 variables. The Guinier powder pattern reveals weaksuperstructure reflections pointing to a TiFeSi-type structural arrangement: I2cm, a = 708.1(1) pm, b = 1225.2(2)pm, c = 869.9(1) pm, wR2 = 0.0787, 5556 F2 values, and 49 variables. So far the growth of high-quality singlecrystals failed. Determination of the superstructure was partly based on merohedral triplet X-ray data augmentedby 119Sn Mössbauer spectroscopy and 119Sn and 45Sc solid-state NMR data. In particular, the observation of threecrystallographically inequivalent sites in 45Sc NMR triple quantum magic-angle spinning (TQ-MAS) NMR spectraprovided unambiguous proof of the superstructure proposed. The ScAgSn structure consists of a three-dimensional[AgSn] network (with Ag−Sn distances between 273 and 280 pm) in which the scandium atoms are located indistorted hexagonal channels, each having five tin and two silver nearest neighbors. Both crystallographicallyindependent tin sites have a tricapped trigonal prismatic coordination, that is, [Sn1Sc6Ag3] and [Sn2Ag6Sc3]environments, which are well distinguished in the 119Sn NMR and Mössbauer spectra because of their different sitesymmetries.
- New stannide ScAgSn crystallizes with the TiFeSi type, a superstructure of ZrNiAl. The determination of the superstructure was based on partly merohedral triplet X-ray data augmented by 119Sn Mössbauer spectroscopy and 119Sn and 45Sc solid-state NMR spectroscopy. Observation of three crystallographically inequivalent sites in the 45Sc NMR triple quantum magic-angle spinning NMR spectra provided unambiguous proof of the superstructure. Both crystallographically independent tin sites have a tricapped trigonal prismatic coordination, which are well distinguished in the 119Sn NMR and Mössbauer spectra.
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