New Indides EuAuIn2, EuPdIn4, GdRhIn2, YbRhIn4, and YbPdIn4

Abstract

New intermetallic indium compounds EuAuIn2, EuPdIn4, GdRhIn2, YbRhln4, and YbPdIn4 were obtained by reaction of the elements. GdRhIn2 was synthesized in an arc-melting furnace, while EuAuIn2, EuPdln4, YbRhIn4, and YbPdIn4 were prepared in sealed tantalum tubes in a high-frequency furnace. The five compounds were investigated by X-ray diffraction both on powders and single crystals. EuAuIn2 and GdRhIn2 adopt the MgCuAl2 type structure with space group Cmcm. Single crystal X-ray data yielded a = 468.1(2), b = 1105.5(4), c = 753.5(4) pm, wR2 = 0.096, 343 F2 values for EuAuIn2 and a = 435.0(1), b = 1013.3(3), c = 783.6(2) pm, wR2 = 0.042, 608 F2 values for GdRhIn2 with 16 variables for each refinement. The two structures may be described as gold or rhodium filled versions of the host lattices Euln2 and GdIn2 . The three-dimensional indium networks of EuAuIn2 and GdRhIn2 resemble the lonsdaleite structure. Both structures are built up from three-dimensional [Auln2] and [Rhln2] poly anions in which the europium and gadolinium atoms occupy distorted hexagonal tubes. The modulations of the In-In distances within the indium networks are compared with other MgCuAl2 type indides. EuPdIn4 and YbPdIn4 crystallize with the YNiAl4 type, space group Cmcm: a = 454.8(2), b = 1703.2(8), c = 738.0(3) pm, wR2 = 0.044, 501 F2 values for EuPdIn4 and a = 445.8(2), b = 1666.0(4), c = 747.3(2) pm, wR2 = 0.050, 711 F2 values for YbPdIn4 with 24 variables for each refinement. In contrast, YbRhln4 adopts the LaCoAl4 type, space group Pmma: a = 863.7(2), b = 422.5(1), c = 743.1(1) pm, wR2 = 0.051, 467 F2 values and 24 variables. EuPdIn4, YbPdlIn4, and YbRhIn4 too consist of three-dimensional [Pdln4] and [Rhln4] polyanions in which the europium and ytterbium atoms are located in distorted hexagonal and pentagonal channels. Common structural motifs of these indides are distorted bcc-like indium cubes which are compared with the structures of Y2CoIn8, YCoIn5, EuRh2ln8, and elemental indium. Chemical bonding in these indides is briefly discussed