Premium
Structure and Lithium Dynamics of Li 2 AuSn 2 —A Ternary Stannide with Condensed AuSn 4/2 Tetrahedra
Author(s) -
Wu Zhiyun,
Mosel Bernd D.,
Eckert Hellmut,
Hoffmann RolfDieter,
Pöttgen Rainer
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200305479
Subject(s) - crystallography , knight shift , lithium (medication) , tin , crystal structure , chemistry , materials science , condensed matter physics , medicine , physics , superconductivity , endocrinology , organic chemistry
Abstract The new stannide Li 2 AuSn 2 was prepared by reaction of the elements in a sealed tantalum tube in a resistance furnace at 970 K followed by annealing at 720 K for five days. Li 2 AuSn 2 was investigated by X‐ray diffraction on powders and single crystals and the structure was refined from single‐crystal data: Z =4, I 4 1 / amd , a =455.60(7), c =1957.4(4) pm, wR2=0.0681, 278 F 2 values, 10 parameters. The gold atoms display a slightly distorted tetrahedral tin coordination with AuSn distances of 273 pm. These tetrahedra are condensed through common corners leading to the formation of two‐dimensional AuSn 4/2 layers. The latter are connected in the third dimension through SnSn bonds (296 pm). The lithium atoms fill distorted hexagonal channels formed by the three‐dimensional [AuSn 2 ] network. Modestly small 7 Li Knight shifts are measured by solid‐state NMR spectroscopy that are consistent with a nearly complete state of lithium ionization. The noncubic local symmetry at the tin site is reflected by a nuclear electric quadrupolar splitting in the 119 Sn Mössbauer spectra and a small chemical shift anisotropy evident from 119 Sn solid‐state NMR spectroscopy. Variable‐temperature static 7 Li solid‐state NMR spectra reveal motional narrowing effects at temperatures above 200 K, revealing lithium atomic mobility on the kHz time scale. Detailed lineshape as well as temperature‐dependent spin lattice relaxation time measurements indicate an activation energy of lithium motion of 27 kJ mol −1 .