Rare-earth germanium autimonides RE6Ge5-xSb11+x (RE = La-Nd, Sm, Gd-Dy). I. Syntheses and structures

The ternary rare-each germanium antimonides RE6Ge5-xSb11+x (RE La-Nd, Sm, G d-Dy) have been synthesized through direct reaction of the elements at 950 degreesC, and the structures of the representative members La6Ge2.8(1)-Sb-1 3.2(1) (a = 4 3034(8) Angstrom, b = 10.551(3) Angstrom, c = 27.073(7) Angst rom), Nd6Ge3.6(1)Sb12.4(1) (a = 4.2310(3) Angstrom, b = 10.6362-(7) Angstro m. c = 26.526(2) Angstrom), and Gd6Ge4.3(1)Sb11.7(1) (a = 4.1509(3) Angstro m, b = 10.4438(7) Angstrom, c = 26.2400(18) Angstrom) have bees determined by single-crystal X-ray diffraction They crysrallize in the orthorhombic sp ace group D-2h(25)-Immm with Z = 2. The structures consist of columns of Sb -centered face-sharing RE6 trigonal prisms aligned along [100]. separated b y interconnecting walls of Ge and Sb atoms. A wide array of Ge-Ge, Ge-Sb, a nd Sb-Sb interactions is found within these walls, ranging from strong cova lent bonds to intermediate one-electron partial bonds to weak van der Waals forces.