The Crystal Structures of Re2Al, Re4Al11, and ReAl6

Abstract

Well-crystallized samples of the rhenium aluminides Re4Al11 and ReAl6 were obtained by reaction of rhenium with an excess of aluminum. Re4Al11 was found to be isotypic with Mn4Al11. The MnAl6 type structure of ReAl6 was confirmed. The crystal structures of both compounds were refined from single-crystal X-ray data. Re4Al11:P1̄, Z = 1, a = 516.0(1) pm, b = 896.3(2) pm, c = 516.9(1) pm, a = 90.44(1)°, β = 99.76(1)°, γ = 105.17(1)°, V = 0.2271 nm3, R = 0.036 for 2315 structure factors and 74 variable parameters. ReAl6: Cmcm, Z = 4, a = 761.0(1) pm, b = 660.5(1) pm, c = 903.4(1) pm, V = 0.4541 nm3, R = 0.013 for 711F values and 23 variables. In both structures the rhenium atoms have ten aluminum neighbors at distances from 245 to 277 pm. The Al-Al distances cover the whole range from 251 to 362 pm rather continuously. The previously reported compound Re2Al with the tetragonal MoSi2-type structure has the lattice constants a = 298.1(1) pm, c = 958.4(4) pm, V = 0.08519 nm3. ReAl6 shows Pauli-paramagnetism.