Sc_2Te: A Novel Example of Condensed Metal Polyhedra in a Metal-Rich but Relatively Electron-Poor Compound

摘要

The earlier transition-metal chalcogenides have both extended the boundaries of solid-state chemistry and challenged our understanding of stability, structure, and bonding. Some recent examples of metal-rich chalcogenides of Group 4 and 5 metals are Ti_9Se_2, Zr_3Te, Hf_3Te_2, Ta_3S_2, and Ta_2Se. Highly reduced binary compounds of the earliest transition metals Sc. Y, La have been limited to a few halides and to the monochalco-genides (NaCl-type), which may be significantly substoichio-metric. Onlya few truly binary halides are known (Sc_7Cl_(10), Y_2X_3, and LaI). No phase diagrams exist for any of the scandium or yttrium chalcogenides, and the only binary Sc-Te phases reported are Sc_2Te_3 and ScTe. This situation clearly results from a lack ofinvestigation of these quite refractory compounds. This article describes the first example, Sc_2Te, an exceptional chalcogenide with respect to the nature of its metal-metal bonding.