Zr11Sb18:: A new binary antimonide exhibiting an unusual Sb atom network with nonclassical Sb-Sb bonding

The herewith-introduced antimonides Zr11Sb18 and Zr10.4V0.6Sb18 were prepared by high-temperature techniques; both arc-melting and solid-state reactions at 1200 degreesC starting from alpha-ZrSb2 and the metals Zr and V in powder form are possible methods, These isostructural compounds represent an unprecedented metal:antimony ratio of 11:18 and form a new structure type. Zr11Sb18 crystallizes in the tetragonal space group 1 (4) over bar 2d, with the lattice dimensions a = 676.94(4) pm and c = 6007.3(5) pm, while the V-containing phase forms a slightly smaller unit cell with a = 676.48(8) pm and c = 6005.6(9) pm (Z= 4). Their structures are comprised of an Sb atom substructure with several intermediate Sb-Sb bonds starting at 311 pm, which is reminiscent of that found in the series (Ti,M)(5)Sb-8 (M = Zr, Hf, Nb, Mo) published last bear. Interwoven with this network is the Zr atom network, which forms a diamond-like metal atom substructure with long Zr-Zr contacts of ca. 360 pm, Band structure calculations based on the linear muffin tin orbital approach reveal these antimonides to be mainly stabilized by strong M-Sb and intermediate Sb-Sb bonds, and additionally-to the smallest extent-by M-M bonds (M = Zr, V). In agreement with the electronic structure calculations, Zr11Sb18 is metallic with a small positive Seebeck coefficient.