The stannides RERhSn (RE = Ho-Yb) and ScTSn (T = Pd, Pt) - Structure refinements and Sn-119 Mossbauer spectroscopy

The stannides RERhSn (RE = Ho - Yb) and ScTSn (T = Pd, Pt) were prepared by reaction of the elements in sealed tantalum tubes in a high-frequency furn ace, by are-melting, or by a tin-flux technique in quartz tubes. The rhodiu m based stannides crystallize with the ZrNiAl type structure, space group P (6) over bar 2m. The four structures were refined from single crystal X-ra y data: a = 754.5(3), c = 377.1(1) pm, wR2 = 0.0357, 233 F-2 values for HoR hSn, a = 753.3(1), c = 372.16(8) pm, wR2 = 0.0721, 233 F-2 values for ErRhS n, a = 753.7(3), c = 369.0(2) pm, wR2 = 0.0671, 233 F-2 values for TmRhSn, and a = 753.17(5), c = 366.53(4) pm, wR2 = 0.0566, 180 F-2 values for YbRhS n with 14 parameters for each refinement. ScPdSn and ScPtSn adopt the HfRhS n type, a superstructure of ZrNiAl, space group P (6) over bar 2c: a = 747. 5(1), c = 710.2(1) pm, for ScPdSn, and a = 738.37(9), c = 729.47(9) pm, wR2 = 0.0452, 369 F-2 values, 18 variables for ScPtSn. Structural motifs in th ese stannides are transition metal centered trigonal prisms formed by the r are earth and tin atoms. While these prisms are regular in the rhodiurn bas ed stannides, significant distortions occur in ScPdSn and ScPtSn. The forma tion of the superstructure can be ascribed to packing reasons. The shortest interatomic distances occur between the transition metal (T) and tin atoms . These atoms form three-dimensional [TSn] networks in which the rare earth atoms fill distorted hexagonal channels. The series RERhSn displays a some what unique behavior. The a lattice parameter is more or less independent o f the rare earth element, while the c lattice parameter shows the expected lanthanoid contraction. Sn-119 Mossbauer spectroscopic data of the rhodiurn stannides show signals at isomer shifts varying from 1.77 to 1.82 mm/s sub ject to quadrupole splitting between 0.75 to 0.82 mm/s.