Ternary Antimonides LnTSb₃ with Ln = La-Nd, Sm and T = V, Cr

Abstract

The title compounds were prepared by reaction of the elemental components. They crystallize in a new structure type, which was determined from single-crystal X -ray data of CeCrSb 3 : Pbcm, a = 1310.8(3), b = 618.4(1), c = 607.9(1) pm, Z = 4, R = 0.029 for 648 structure factors and 32 variable parameters. The structure of the antimonide CeVSb 3 is isotypic: a = 1319.0(2), b = 623.92(8), c = 603.03(8) pm , R = 0.041 for 477 structure factors and 32 variables. The transition metal site and one of the three antimony sites were found to have partial occupancies resulting in the exact compositions CeV 0,91(1) Sb 2,916(4) and CeCr 0,901(9) Sb 2,909(4) . The structures contain fractional Sb -Sb bonds with distances varying between 301,5 and 316.4 pm. The transition metal atoms have octahedral antimony coordination. These TSb 6 octahedra share faces resulting in linear infinite strings with V - V and Cr - Cr bond distances of 301.5 and 304.0 pm, respectively. The structure of these com pounds contains building elements, which are also found in antimonides with ThCr 2 Si 2 , CaBe 2 Ge 2 , and HfCuSi 2 type structures.