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)o, 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)o, 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)o, 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. - Graphical abstract: Crystal structure of Dy5Ni2In4