RhSn3 and the Modifications of RhSn4-Structure and 119Sn Mössbauer spectroscopic characterization

Abstract

Single crystals of the higherature modification of RhSn4 were obtained from a tin flux (1:20 molar ratio; final annealing at 920 K; dissolution of the tin matrix in 2N HCl). The structure was refined from single-crystal X-ray diffractometer data: I41/acd, a=629.73(5), c=2288.36(18) pm, wR2=0.0382, 447 F2 values and 14 variables. β-RhSn4 is isotypic with β-IrSn4. The rhodium atoms have slightly distorted square-antiprismatic tin coordination with Rh-Sn distances of 4×273.4 and 4×274.1 pm. The RhSn8 units are condensed via common edges to layers that are staggered with respect to each other and stacked in ABCD sequence. A 119Sn Mössbauer spectroscopic characterization of ß-RhSn4 and the stannides RhSn3 and α-RhSn4 shows the typical isomer shifts for transition metal stannides. Only for α-RhSn4 the three crystallographically independent tin sites could be resolved, a consequence of the different s-electron density. Treatment of α-RhSn4 under high-pressure (up to 10 GPa)/higherature (up to T=1370 K) conditions leads to decomposition into Rh1.5Sn, RhSn2 and β-Sn.