The First Titanium Molybdenum Antimonide: Ti_5.42Mo_2.58Sb₉, a Substitution Variant of Zr₂V₆Sb₉

Abstract

The new ternary antimonide Ti_5.42(2)Mo_2.58Sb₉ was uncovered by a reaction of the elements under exclusion of air at 1150 °C. It crystallizes in a ternary substitution variant of the V_7.5Sb₉ type, a structure not known to exist in either the Ti/Sb or the Mo/Sb system. The crystal structure of Ti_5.42Mo_2.58Sb₉ was determined from single crystal X-ray data: space group P4/nmm, with a = 9.8178(8) Å, c = 7.1857(8) Å, V = 692.6(1) ų, Z = 2, R1 = 0.025, wR2 = 0.052 (all data). The structure contains four metal atom sites, two thereof occupied solely by Ti atoms, and two by different Ti/Mo mixtures. The former two correspond to the Zr sites, and the latter two to the V sites of the isostructural antimonide Zr₂V₆Sb₉. The crystal structure is comprised of chains of face-sharing TiSb₈ square antiprisms, Ti/Mo tetrahedra and Sb atom pairs and squares. The electronic structure, computed with the LMTO approximation, is indicative of metallic properties. In addition to the dominating metal–Sb bonds, strong metal–metal and Sb–Sb bonds exist as well in Ti_5.42Mo_2.58Sb₉. The Mo content per metal site increases with increasing metal–metal interactions.