Crystal Growth, Structures, and Properties of the Complex Borides, LaOs2Al2B and La2Os2AlB2

• Published in: Inorganic chemistry Vol. 54; no. 16; pp. 8049 - 8057
• Main Authors: Bugaris, Daniel E, Han, Fei, Im, Jino, Chung, Duck Young, Freeman, Arthur J, Kanatzidis, Mercouri G
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17.08.2015
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.5b01275

Single crystals of two novel quaternary metal borides, LaOs2Al2B and La2Os2AlB2, have been grown from La/Ni eutectic fluxes. LaOs2Al2B crystallizes in tetragonal space group P4/mmm with the CeCr2Si2C-type structure, and lattice parameters a = 4.2075(6) Å and c = 5.634(1) Å. La2Os2AlB2 exhibits a new crystal structure in monoclinic space group C2/c with lattice parameters a = 16.629(3) Å, b = 6.048(1) Å, c = 10.393(2) Å, and β = 113.96(3)°. Both structures are three-dimensional frameworks with unusual coordination (for solid-state compounds) of the boron atoms by transition metal atoms. The boron atom is square planar in LaOs2Al2B, whereas it exhibits linear and T-shaped geometries in La2Os2AlB2. Electrical resistivity measurements reveal poor metal behavior (ρ300 K ∼ 900 μΩ cm) for La2Os2AlB2, consistent with the electronic band structure calculations, which also predict a metallic character for LaOs2Al2B.