Rare-Earth Germanium Antimonides RE₆Ge_5-xSb_11+x (RE = La−Nd, Sm, Gd−Dy). I. Syntheses and Structures

Abstract

The ternary rare-earth germanium antimonides RE6Ge5-xSb11+x (RE = La−Nd, Sm, Gd−Dy) have been synthesized through direct reaction of the elements at 950 °C, and the structures of the representative members La6Ge2.8(1)Sb13.2(1) (a = 4.3034(8) Å, b = 10.851(3) Å, c = 27.073(7) Å), Nd6Ge3.6(1)Sb12.4(1) (a = 4.2310(3) Å, b = 10.6362(7) Å, c = 26.526(2) Å), and Gd6Ge4.3(1)Sb11.7(1) (a = 4.1509(3) Å, b = 10.4438(7) Å, c = 26.2400(18) Å) have been determined by single-crystal X-ray diffraction. They crystallize in the orthorhombic space group -Immm with Z = 2. The structures consist of columns of Sb-centered face-sharing RE6 trigonal prisms aligned along [100], separated by interconnecting walls of Ge and Sb atoms. A wide array of Ge−Ge, Ge−Sb, and Sb−Sb interactions is found within these walls, ranging from strong covalent bonds to intermediate one-electron partial bonds to weak van der Waals forces.