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

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, Sc₆Au_0.856(2)Te₂, and Sc₆Au_0.892(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