The new ternary transition-metal tellurides TaIrTe4 and NbIrTe4 are ordered variants of the WTe2 structure, which in turn is based on a distortion of the CdI2-type layered structure. The layers in WTe2 consist of buckled sheets of Te atoms, with the metal atoms residing in distorted octahedral sites. Through single-crystal X-ray diffraction methods, the structure of TaIrTe4 has been determined and that of WTe2 has been redetermined. The compounds TaIrTe4 and WTe2 belong to the space group C72v-Pmn21 of the orthorhombic system with four formula units in cells of dimensions a = 3.770 (1), b = 12.421 (6), and c = 13.184 (6) Å and a = 3.477 (2), b = 6.249 (4), and c = 14.018 (9) Å, respectively, at 113 K. While metal-metal bonding is a structural feature common to all three compounds, Te-Te bonding is observed only in the ternary compounds. The trends of increasing metal-metal and decreasing Te-Te distances on progressing from WTe2 to TaIrTe4 and NbIrTe4 have been rationalized by electronic band (extended Hückel) calculations. These trends are related to the creation of Te-Te bonds, ensuring the stability of the WTe2 structure type even when addition of more d electrons leads to a weakening of metal-metal bonds. This concept is generalized to an entire series of compounds MM′Te4 (M = Nb, Ta; M′ = Ru, Os, Rh, Ir).
ASJC Scopus subject areas
- Colloid and Surface Chemistry