Gold Derivatives of Eight Rare-Earth-Metal-Rich Tellurides: Monoclinic R₇Au₂Te₂ and Orthorhombic R₆AuTe₂ Types

Abstract

Two series of rare-earth-metal (R) compounds, R7Au2Te2 (R = Tb, Dy, Ho) and R6AuTe2 (R = Sc, Y, Dy, Ho, Lu), have been synthesized by high-temperature techniques and characterized by X-ray diffraction analyses as monoclinic Er7Au2Te2-type and orthorhombic Sc6PdTe2-type structures, respectively. Single-crystal diffraction results are reported for Ho7Au2Te2, Lu6AuTe2, Sc6Au0.856(2)Te2, and Sc6Au0.892(3)Te2. The structure of Ho7Au2Te2 consists of columns of Au-centered tricapped trigonal prisms (TCTPs) of Ho condensed into 2D zigzag sheets that are interbridged by Te and additional Ho to form the 3D network. The structure of Lu6AuTe2 is built of pairs of Au-centered Lu TCTP chains condensed with double Lu octahedra in chains into 2D zigzag sheets that are separated by Te atoms. Tight binding–linear muffin-tin orbital–atomic sphere approximation electronic structure calculations on Lu6AuTe2 indicate a metallic property. The principal polar Lu–Au and Lu–Te interactions constitute 75% of the total Hamilton populations, in contrast to the small values for Lu–Lu bonding even though these comprise the majority of the atoms. A comparison of the theoretical results for Lu6AuTe2 with those for isotypic Lu6AgTe2 and Lu6CuTe2 provides clear evidence of the greater relativistic effects in the bonding of Au. The parallels and noteworthy contrasts between Ho7Au2Te2 (35 valence electrons) and the isotypic but much electron-richer Nb7P4 (55 valence electrons) are analyzed and discussed