Rare earth–nickel–indides Dy5Ni2In4 and RE4Ni11In20 (RE=Gd, Tb, Dy)

The new rare earth metal (RE)–nickel–indides Dy5Ni2In4 and RE4Ni11In20 (RE=Gd, Tb, Dy) were synthesized from the elements by arc-melting. Well-shaped single crystals were obtained by special annealing sequences. The four indides were investigated by X-ray diffraction on powders and single crystals: Lu5Ni2In4 type, Pbam, Z=2, a=1784.2(8), b=787.7(3), c=359.9(1) pm, wR2=0.0458, 891 F2 values, 36 variables for Dy5Ni2In4, U4Ni11Ga20 type, C2/m, a=2254.0(9), b=433.8(3), c=1658.5(8) pm, β=124.59(2)°, wR2=0.0794, 2154 F2 values, 108 variables for Gd4Ni11In20, a=2249.9(8), b=432.2(1), c=1657.9(5) pm, β=124.59(2)°, wR2=0.0417, 2147 F2 values, 108 variables for Tb4Ni11In20, and a=2252.2(5), b=430.6(1), c=1659.7(5) pm, β=124.58(2)°, wR2=0.0550, 2003 F2 values, 109 variables for Dy4Ni10.80In20.20. The 2d site in the dysprosium compound shows mixed Ni/In occupancy. Most nickel atoms in both series of compounds exhibit trigonal prismatic coordination by indium and rare earth atoms. Additionally, in the RE4Ni11In20 compounds one observes one-dimensional nickel clusters (259 pm Ni1–Ni6 in Dy4Ni10.80In20.20) that are embedded in an indium matrix. While only one short In1–In2 contact at 324 pm is observed in Dy5Ni2In4, the more indium-rich Dy4Ni10.80In20.20 structure exhibits a broader range in In–In interactions (291–364 pm). Together the nickel and indium atoms build up polyanionic networks, a two-dimensional one in Dy5Ni2In4 and a complex three-dimensional network in Dy4Ni10.80In20.20. These features have a clear consequence on the dysprosium coordination, i.e. a variety of short Dy–Dy contacts (338–379 pm) in Dy5Ni2In4, while the dysprosium atoms are well separated (430 pm shortest Dy–Dy distance) within the distorted hexagonal channels of the [Ni10.80In20.20] polyanion of Dy4Ni10.80In20.20. The crystal chemistry of both structure types is comparatively discussed.

Crystal structure of Dy5Ni2In4.Figure optionsDownload as PowerPoint slide