Ternary Rare Earth Metal Palladium and Platinum Aluminides R4Pd9Al24 and R4Pt9Al24

The fifteen intermetallic compounds R₄Pd₉Al₂₄ (R = Gd–Tm) and R₄Pt₉Al₂₄ (R = Y, Gd–Lu) were prepared by reaction of the elemental components. Their crystal structure was determined from single-crystal X-ray data of Er₄Pt₉Al₂₄. It is pseudo-trigonal with triclinic symmetry: P 1, a = b = 747.5(2) pm, c = 1306.7(4) pm, α = 100.99(2)°, β = 95.47(2)°, γ = 60.00(3)°, Z = 1, R = 0.052 for 2593 structure factors and 110 variable parameters. The structure is closely related to that of Y₂Co₃Ga₉. Both may be described as stacking variants of each other. They consist of layers of the compositions PtAl₂ (CoGa₂), and Er₂Al₃ (Y₂Ga₃), designated A and B, respectively. These layers are stacked in the five- and four-layer sequences ABAAB (Er₄Pt₉Al₂₄) and ABAB (Y₂Co₃Ga₉). The layers PtAl₂ and CoGa₂ are similar to the hexagonal close packed layers in the TiSi₂-, CrSi₂-, and MoSi₂-type structures. The structure of Er₄Pt₉Al₂₄ contains a monoclinic subcell, where the layers Er₂Al₃ are disordered. A partial disorder of this kind, which could be ascribed to twinning or to the intergrowth with another stacking variant, was found during the structure refinement of the isotypic compound Y₄Pt₉Al₂₄: a = b = 749.0(2) pm. c = 1309.3(4) pm, α = 100.99(2)°, β = 95.48(2)°, γ = 60.00(3)°, R = 0.031 for 1435 structure factors and 128 variable parameters.     

Ternary Aluminides with the Ideal Composition A2Pt6Al15 (A = Y,Gd—Tm,Zr)

Ternary rare earth platinum aluminides were prepared by arc‐melting of the elemental components followed by annealing in a high‐frequency furnace. Their crystal structure was determined for the yttrium compound from four‐circle X‐ray diffractometer data. It has hexagonal symmetry with a = 428.1(1) pm, c = 1638.3(3) pm, space group P6₃/mmc, and was refined to a conventional residual of R = 0.018 for 325 F values and 19 variable parameters. Of the five crystallographic positions, the yttrium position and one of the three aluminum positions show partial occupancies corresponding to the composition Y_1.357(3)Pt₄Al_9.99(2) with the Pearson symbol hP20 — 4.65. These partially occupied sites are that close to each other that at best only one can be fully occupied. A model for an ordered distribution of occupied and unoccupied Y and Al sites requires a √3 larger a axis with the Pearson symbol hP20 — 4.67 for the subcell, very close to the experimental result. Corresponding superstructure reflections could be observed on an image‐plate single‐crystal diffractometer only in the form of diffuse streaks. The compound has the ideal composition Y₂Pt₆Al₁₅ with Z = 2 for the superstructure. This corresponds to the formula Y_1.33Pt₄Al₁₀ with Z = 1 for the subcell. The compounds A_1.33Pt₄Al₁₀ with A = Gd, Tb, Dy, Ho, Er, Tm were found to be isotypic with that of the yttrium compound. This structure is closely related to or isotypic with, respectively, those of Yb₂Fe₄Si₉, Sc_1.2Fe₄Si_9.8, Ce_1.2Pt₄Ga_9.8, Ce₂Pt₆Ga₁₅, Tb_0.67Ni₂Ga_5—xSi_x, RE_0.67Ni₂Ga_5—xGe_x> (with RE = Y, Sm, Ho), and Gd_0.67Pt₂Al₅, reported in earlier investigations. The new compound Zr_1.00(1)Pt₄Al_10.22(3) has nearly the same hexagonal structure with a = 426.1(1) pm and c = 1622.8(3) pm. It was refined from four‐circle diffractometer data to a residual of R = 0.021 for 288 structure factors and 19 variable parameters.     

Rare Earth Metal Ruthenium Gallides R2Ru3Ga9 with Y2Co3Ga9 Type Structure

The twelve isotypic intermetallic compounds R₂Ru₃Ga₉ with R = Y, La–Nd, Sm, Gd–Tm were prepared by arc‐melting of the elemental components. Their crystal structure was determined from single‐crystal X‐ray data of Dy₂Ru₃Ga₉: Cmcm, a = 1279.3(2) pm, b = 755.6(1) pm, c = 964.7(1) pm, Z = 4, R = 0.020 for 671 structure factors and 42 variable parameters. All atomic positions have within two standard deviations ideal occupancies (occupancy values vary between 98.8(5) and 101.2(6)%). The structure is briefly discussed, emphasizing its relation to other structures with a high content of gallium or aluminum.     

Preparation and Crystal Structures of Ternary Rare Earth Osmium Gallides LnOsGa3 (Ln = Gd—Tm) and LnOsGa3 (Ln = La—Nd)

The title compounds were prepared from the elemental components at high temperatures. The compounds LnOsGa₃ crystallize with the cubic TmRuGa₃ type structure which was refined from four‐circle X‐ray diffractometer data of TbOsGa₃: Pm3¯m, Z = 3, a = 640.8(1) pm, R = 0.014 for 173 structure factors and 10 variable parameters. The other gallides crystallize with a new structure type which was determined from single‐crystal X‐ray data of CeOsGa₄: Pmma, Z = 6, a = 963.9(2) pm, b = 880.1(1) pm, c = 767.0(1) pm, R = 0.030 for 744 F values and 56 variables. The structure may be considered as consisting of two kinds of alternating layers, although bonding within and between the layers is of similar strength. One kind of layers (A) is slightly puckered, two‐dimensionally infinite, hexagonal close packed, with the composition OsGa₃; the other kind of layers (B) is planar with the composition CeGa. The structure is closely related to that of Y₂Co₃Ga₉ where the corresponding layers have the compositions Co₃Ga₆ (A) and Y₂Ga₃ (B).     

Rare earth-rich cadmium compounds RE 4 TCd (T = Co, Ru, and Rh) with Gd4RhIn type structure

The rare earth-rich cadmium compounds RE ₄ TCd (RE = Y, La–Nd, Sm, and Gd–Tm, Lu; T = Co, Ru, and Rh) were prepared from the elements in sealed tantalum ampoules in an induction furnace. All samples were characterized by X-ray powder diffraction. The structures of Y₄RuCd (a = 1362.5(1) pm), La₄RuCd (a = 1415.9(1) pm), Gd₄RuCd (a = 1368.8(2) pm), La₄CoCd (a = 1417.9(4) pm), Gd₄CoCd (a = 1356.1(1) pm), and Gd₄RhCd (a = 1368.7(1) pm) were refined from single crystal X-ray diffractometer data. The RE ₄ TCd compounds crystallize with the cubic Gd₄RhIn type structure, space group F ${\bar 4}The rare earth-rich cadmium compounds RE ₄ TCd (RE = Y, La–Nd, Sm, and Gd–Tm, Lu; T = Co, Ru, and Rh) were prepared from the elements in sealed tantalum ampoules in an induction furnace. All samples were characterized by X-ray powder diffraction. The structures of Y₄RuCd (a = 1362.5(1) pm), La₄RuCd (a = 1415.9(1) pm), Gd₄RuCd (a = 1368.8(2) pm), La₄CoCd (a = 1417.9(4) pm), Gd₄CoCd (a = 1356.1(1) pm), and Gd₄RhCd (a = 1368.7(1) pm) were refined from single crystal X-ray diffractometer data. The RE ₄ TCd compounds crystallize with the cubic Gd₄RhIn type structure, space group F 3m. The transition metal atoms have tricapped trigonal prismatic rare earth coordination. The trigonal prisms are condensed via common edges, forming a rigid three-dimensional network with adamantane symmetry. Voids in these networks are filled by Cd₄ tetrahedra (304 pm Cd–Cd in Gd₄CoCd) and polyhedra of the RE1 atoms. The crystal chemical peculiarities are briefly discussed. Correspondence: Rainer P?ttgen, Institut für Anorganische und Analytische Chemie, Westf?lische Wilhelms-Universit?t Münster, Correnstrasse 30, 48149 Münster, Germany.     

Ternary Transition Metal Antimonides T5T' 1‐xSb2+x (T = Ti,Zr, Hf; T' = Fe,Co, Ni,Cu, Ru,Rh, Pd,Cd) with Nb5SiSn2 (Ordered W5Si3, Filled V4SiSb2) Type Structure

Fifteen new ternary antimonides T₅T' _1‐xSb_2+x were synthesized by reaction of the elemental components in an arc‐melting furnace. They crystallize with a tetragonal structure first reported for Nb₅SiSn₂ (space group I4/mcm, Z = 4.) A structure refinement from four‐circle X‐ray diffractometer data of Hf₅Fe_1‐xSb_2+x (a = 1086.0(1) pm, c = 550.1(1) pm, R = 0.033 for 270 structure factors and 18 variable parameters) showed deviations from the ideal occupancy for two atomic sites, resulting in the composition Hf_4.929(3)Fe_0.67(1)Sb_2.33(1). Structure refinements from X‐ray powder data resulted in the formula Ti₅Ni_0.45(2)Sb_2.55(2), while no deviation from the ideal composition was observed for Ti₅RhSb₂. The crystal structures of these compounds are discussed together with those of related binary and ternary compounds.     

Preparation,Crystal Structure,and Magnetic Properties of Rare Earth Ruthenium and Osmium Carbides with La3.67FeC6 Type Structure

The new carbides Gd_3.67RuC₆ and Ln_3.67OsC₆ (Ln = La–Nd, Sm) were prepared by arc‐melting of cold‐pressed pellets of the elemental components. Their hexagonal (P6₃/m) La_3.67FeC₆ type crystal structure was refined from X‐ray powder diffraction data of La_3.67OsC₆ (a = 889.1(1) pm, c = 535.1(1) pm) and Pr_3.67OsC₆ (a = 874.9(2) pm, c = 523.7(1) pm). The occupancy parameters of one La and one Pr site were refined to 0.35(5) and 0.34(5), respectively, in agreement with the highest possible occupancy for steric reasons of 1/3. The C–C distances in the C₂ pairs are 139(6) pm and 137(3) pm, respectively, indicating double bonds. The environment of the osmium atoms is compatible with the 18‐electron rule. The magnetic properties of several carbides were determind with a SQUID magnetometer. The lanthanum compounds La_3.67RuC₆ and La_3.67OsC₆ are Pauli paramagnetic. The magnetic properties of the other compounds are dominated by the magnetic moments of the rare earth atoms. Most order ferrimagnetically with Curie temperatures varying between 5(± 3) and 32(± 6) K for Ce_3.67OsC₆ and Pr_3.67RuC₆, respectively. The cerium atoms in Ce_3.67RuC₆ and Ce_3.67OsC₆ are essentially trivalent, and the samarium compounds show Van Vleck behavior.     

Rare earth-copper-magnesium compounds RECu9Mg2 (RE=Y, La-Nd, Sm-Ho, Yb) with ordered CeNi3-type structure

A series of ternary compounds RECu₉Mg₂ (RE=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb) have been synthesized via induction melting of elemental metal ingots followed by annealing at 400 °C for 4 weeks. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS) was used for examining microstructure and phase composition. These phases crystallize with an ordered version of the binary hexagonal structure type first reported for CeNi₃. The crystal structure was solved for TbCu₉Mg₂ from single crystal X-ray counter data (TbCu₉Mg₂-structure type, P6₃/mmc-space group, hP24-Pearson symbol, a=0.49886 (7) nm, c=1.61646 (3) nm, R_F=0.0474 for 190 unique reflections). The Rietveld refinement of the X-ray powder diffraction patterns of RECu₉Mg₂ confirmed the same crystal structure for the reported rare earth metals. The unit cell volumes for RECu₉Mg₂ smoothly follow the lanthanide contraction. The existence of a RECu₉Mg₂ phase was excluded for RE=Er and Tm under the investigated experimental conditions.     

The Ternary Lanthanoid Nickel Arsenides Tb12Ni30As21 and Dy12Ni30As21 with (La,Ce)12Rh30P21 Type Related Structure

The title compounds were synthesized from the elements by reactions at high temperature. They crystallize with a hexagonal structure which was determined from single‐crystal X‐ray data of Dy₁₂Ni₃₀As₂₁: P6₃/m, Z = 1, a = 1698.5(5) pm, c = 387.7(1) pm, R = 0.053 for 797 F values and 69 variable parameters. It belongs to a large family of hexagonal structures with a metal to metalloid ratio of 2 : 1. In these hexagonal structures an ordered distribution of occupied atomic positions around the hexagonal 6₃ axis is possible only for refinements in space groups of lower symmetry. This is discussed for the present case and the very closely related structures reported for (La, Ce)₁₂Rh₃₀P₂₁ and Nd₃Ni₇P₅.     

Gd3Pt4In12 and Tb3Pt4In12 — New Ternary Indides with Condensed Distorted [PtIn6] Trigonal Prisms

The ternary indium compounds Gd₃Pt₄In₁₂ and Tb₃Pt₄In₁₂ were synthesized from an indium flux. Arc‐melted precursor alloys with the starting compositions ∼GdPtIn₄ and ∼TbPtIn₄ were annealed with a slight excess of indium at 1200 K followed by slow cooling (5 K/h) to 870 K. Both compounds were investigated by X‐ray powder diffraction: a = 990.5(1), c = 1529.5(3) pm for Gd₃Pt₄In₁₂ and a = 988.65(9), c = 1524.0(1) pm for Tb₃Pt₄In₁₂. The structure of the gadolinium compound was solved and refined from single crystal X‐ray data: P3¯m1, wR2 = 0.0470, 1469 F² values and 62 variable parameters. Both crystallographically different platinum sites have a slightly distorted trigonal prismatic indium coordination. These [PtIn₆] prisms are condensed via common edges and corners forming a complex three‐dimensional [Pt₁₂In₃₂] network. The gadolinium, In1 and In7 atoms fill cavities within this polyanion. Tb₃Pt₄In₁₂ is isotypic with the gadolinium compound.     

The First Rare Earth Metal Thioborate: Synthesis and Crystal Structure of EuB2S4

Systematic studies on thio‐ and selenoborates containing heavier metal cations led to the new crystalline phase EuB₂S₄. The crystal structure of the europium metathioborate reveals polymeric [(B₂S₄)^2—]_n anions and divalent Eu‐cations which are connected via ionic interactions. The building blocks of the anions consist of BS₄‐tetrahedra. Condensation of these BS₄‐tetrahedra leads to corner‐ and edge‐sharing 2D‐networks running parallel to (1 0 0). Evacuated carbon coated silica tubes were used as reaction vessels since temperatures up to 990 K were applied. EuB₂S₄ crystallizes in the monoclinic space group P2₁/c (no. 14) with a = 6.4331(6)Å, b = 14.099(1)Å, c = 6.0731(6)Å, β = 110.55(8)° and Z = 4.     

Crystal Structure of the RE2PbS4 (RE = Y,Dy, Ho,Er, and Tm) Compounds and a Comparison with the Crystal Structures of other Rare Earth Lead Chalcogenides

The crystal structure of the RE₂PbS₄ (RE = Y, Dy, Ho, Er and Tm) compounds (space group Cmc2₁, Pearson symbol oC112, a = 0.79301(3) nm, b = 2.86966(9) nm, c = 1.20511(5) nm, R_Bragg = 0.0979 for Y₂PbS₄; a = 0.79484(8) nm, b = 2.8721(3) nm, c = 1.2039(1) nm, for Dy₂PbS₄; a = 0.79081(2) nm, b = 2.86222(7) nm, c = 1.20220(4) nm, R_Bragg = 0.0859 for Ho₂PbS₄; a = 0.7863(2) nm, b = 2.8525(5) nm, c = 1.1995(2) nm, R1 = 0.0482 for Er₂PbS₄ and a = 0.78419(3) nm, b = 2.84184(9) nm, c = 1.19655(4) nm, R_Bragg = 0.0893 for Tm₂PbS₄) was investigated by means of X‐ray single crystal and powder diffraction. Each RE atoms is octahedrally coordinated by six S atoms. Each Pb atoms is surrounded by seven S atoms to form a mono‐capped trigonal prism.     

Synthesis and Structure of the Intermetallic Lithium Stannides LiTSn4 (T = Ru,Rh, Ir) with Ordered PdGa5 Type Structure

LiRuSn₄, LiRhSn₄, and LiIrSn₄ were prepared by reaction of the elements in sealed tantalum ampoules at 1220 K. The tubes were subsequently annealed at 870 K for one week. The three stannides were investigated by X‐ray diffraction on powders and single crystals and the structures were refined from single crystal data: I4/mcm, a = 662.61(3), c = 1116.98(7) pm, wR2 = 0.0730, 283 F² values for LiRuSn₄, a = 658.73(5), c = 1136.4(1) pm, wR2 = 0.0532, 313 F² values for LiRhSn₄ and a = 657.34(5), c = 1130.4(1) pm, wR2 = 0.0343, 176 F² values for LiIrSn₄ with 11 variables for each refinement. LiRuSn₄, LiRhSn₄, and LiIrSn₄ crystallize with a ternary ordered variant of the PdGa₅ structure. The transition metal (T) atoms have a square antiprismatic tin environment and they form two‐dimensional [TSn₄] polyanions with relatively short Ru—Sn (279 pm), Rh—Sn (280 pm), and Ir—Sn (280 pm) distances. The lithium atoms connect the polyanionic [TSn₄] layers. They are located in square prismatic voids formed by tin atoms. The crystal chemistry and chemical bonding of these stannides is briefly discussed.     

Nd4.67Ru3Mg8.83 – A Magnesium‐rich Compound with Ru@Mg4Nd4 Square Antiprisms and Mg@Mg8 Cubes as ­Basic Building Units

The magnesium‐rich intermetallic compound Nd_4.67Ru₃Mg_8.83 was synthesized from the elements in a sealed tantalum tube in a resistance furnace. Nd_4.67Ru₃Mg_8.83 was characterized by X‐ray powder and single crystal diffraction: new structure type,I4/mmm, tI66, a = 946.0(1), c = 1789.5(4) pm, wR2 = 0.0368, 725 F² values and 36 variables. Two of the five crystallographically independent magnesium sites show a small degree of Mg/Nd mixing. The ruthenium atoms have square anti‐prismatic Nd₄Mg₄ coordination. Always six of such anti‐prisms are condensed via common edges, leading to a CsCl analogous neodymium coordination for the Mg4 atoms. The two‐dimensional networks of edge‐sharing Ru@Nd₄Mg₄ antiprisms are condensed to a three‐dimensional network via Mg5@Mg3₄Mg1₄ cubes. The extended magnesium substructure shows a broad range of Mg–Mg distances from 308 to 351 pm.     

Quaternary indides LaTIn3Mg (T = Rh and Ir) and CeIrIn3Mg with LaCoAl4 type structure

The quaternary indides LaTIn₃Mg (T = Rh and Ir) and CeIrIn₃Mg were prepared from the elements in sealed tantalum ampoules in an induction furnace. The samples were characterized by X-ray powder and single crystal data: LaCoAl₄ type, Pmma, Z = 2, a = 830.5(1), b = 436.1(1), c = 745.1(1) pm, wR2 = 0.038, 467 F ² values for LaRhIn_3.075Mg_0.925, a = 832.9(1), b = 436.5(1), c = 746.9(1) pm, wR2 = 0.077, 471 F ² values for LaIrIn_3.091Mg_0.909, and a = 832.2(1), b = 434.1(1), c = 743.9(1) pm, wR2 = 0.066, 465 F ² values for CeIrIn_3.07Mg_0.93 with 25 variables for each refinement. The transition metal, indium, and magnesium atoms build up three-dimensional [TIn₃Mg] networks which leave pentagonal prismatic voids for the lanthanum and cerium atoms. The transition metal atoms have tricapped trigonal prismatic coordination and the magnesium atoms fill distorted square prisms. All three crystals revealed a small degree of Mg/In mixing on the latter site.     

Rare earth-rich compounds RE9TMg4 (RE = Y,Dy-Tm,Lu; T = Ru,Rh, Os,Ir) with an ordered Co2Al5-type structure

The rare earth-rich intermetallic phases RE₉TMg₄ (RE = Y, Dy-Tm, Lu; T = Ru, Rh, Os, Ir) were synthesized by induction melting of the elements using sealed niobium ampoules as crucible material. The melted samples were additionally annealed in muffle furnaces and subsequently characterized by X-ray powder diffraction. The RE₉TMg₄ compounds adopt an ordered Co₂Al₅ type structure, space group P6₃/mmc. Four structures were refined from single-crystal X-ray diffractometer data: a = 953.71(5), c = 968.41(5) pm, wR2 = 0.00273, 603 F² values, 21 parameters for Tm_8.76RuMg_4.24; a = 958.37(5), c = 975.66(5), wR2 = 0.00384, 661 F² values, 20 parameters for Dy₉OsMg₄; a = 943.70(5), c = 967.91(5) pm, wR2 = 0.00430, 592 F² values, 21 parameters for Tm_8.74OsMg_4.26; a = 968.09(5), c = 978.25(5) pm, wR2 = 0.0439, 623 F² values, 21 parameters for Y_9.18IrMg_3.82. The compounds are prone to small homogeneity ranges (RE/Mg mixing). The transition metal atoms have tricapped trigonal prismatic rare earth coordination. These T@RE₉ units (TP) are condensed with empty RE₆ octahedra (O) via common triangular faces forming infinite strands with a sequence –TP–O–O–. These strands show the motif of hexagonal rod packing and they are separated by chains of edge- and corner-sharing tetrahedra. The magnesium substructures in the hexagonal Laves phase YMg₂ and the prototype Y₉CoMg₄ are structurally closely related. Charge transfer trends, electronic band structures and bonding properties were studied within DFT. The resulting picture is that cobalt brings covalent character by reducing the overall charge transfer and modifies the Laves phase YMg₂ by providing larger localization in the density of states. The Y–Co bonding in Y₉CoMg₄ prevails while weakening the Y–Mg bonds. The investigations of the magnetic properties of selected RE₉TMg₄ compounds revealed Pauli paramagnetic behavior for Y₉CoMg₄, Y₉OsMg₄ and Y₉IrMg₄. A ferromagnetic ground state with Curie temperatures of 46.0 and 47.6 K was observed for Dy₉RuMg₄ and Dy₉OsMg₄, respectively. Ho₉RuMg₄, Ho₉OsMg₄ and Tm₉OsMg₄ reveal antiferromagnetic ordering with Neél temperatures below 20 K.     

Alkaline Earth Transition Metal Antimonides AT4Sb12 (A = Ca,Sr, Ba; T = Fe,Ru, Os) with LaFe4P12-Structure

The title compounds were prepared by reaction of CaSb₂, SrSb₂, or BaSb₃ with the transition metals and antimony in sealed silica tubes. They crystallize with the cubic LaFe₄P₁₂-structure, which was refined from single-crystal X-ray data of CaFe₄Sb₁₂, SrRu₄Sb₁₂, and BaRu₄Sb₁₂ to residuals of R = 0.014, 0.016, and 0.014, respectively. The thermal parameters of the alkaline earth ions increase with decreasing ionic size. The Sb? Sb distances are greater in the iron compound than they are in the two ruthenium compounds. This is rationalized to be due to a larger portion of electrons in antibonding Sb? Sb states in the iron compound.     

[Eu2(TCM)2(DMSO)6]·2DMSO双核笼状稀土配合物的合成与结构

报道一个H3TCM配体在较小尺寸的溶剂DMSO中与稀土离子Eu3+通过自组装形成的双核笼状结构, 从中可进一步看出溶剂分子的尺寸对该双核结构的影响.     

Ternary Rare Earth (RE) Gold Compounds REAuCd and RE2Au2Cd

New intermetallic rare earth compounds REAuCd (RE = Y, La–Nd, Sm–Yb) and RE₂Au₂Cd (RE = La, Pr, Nd, Sm) were prepared by reaction of the elements in sealed tantalum tubes in a high‐frequency furnace. The compounds were investigated by X‐ray diffraction both on powders and single crystals. The equiatomic REAuCd compounds with RE = Y, La–Nd, Sm, and Gd–Tm adopt the ZrNiAl type structure with space group P62m. Single crystal X‐ray data yielded a = 786.2(2), c = 415.9(1) pm, wR2 = 0.0337, 402 F² values for LaAuCd and a = 782.91(9), c = 410.01(5) pm, wR2 = 0.0653, 395 F² values for CeAuCd with 14 parameters for each refinement. Geometrical motifs in CeAuCd are two types of gold centered tricapped trigonal prisms: [Au1Cd₃Ce₆] and [Au2Cd₆Ce₃]. The gold and cadmium atoms form a three‐dimensional [AuCd] polyanion in which the cerium atoms fill distorted hexagonal channels. EuAuCd and YbAuCd crystallize with a TiNiSi type structure, space group Pnma: a = 755.2(1), b = 450.59(5), c = 878.6(1) pm, wR2 = 0.0904, 500 F² values for EuAuCd, and a = 731.64(3), b = 432.94(2), c = 875.80(4) pm, wR2 = 0.1192, 457 F² values for YbAuCd with 20 parameters for each refinement. In these structures the europium(ytterbium) and cadmium atoms form zig‐zag chains of egde‐ and face‐sharing trigonal prisms which are centered by the gold atoms. Also in EuAuCd and YbAuCd a three‐dimensional [AuCd] polyanion occurs in which the europium(ytterbium) atoms are embedded. Europium and ytterbium are divalent in EuAuCd and YbAuCd. Susceptibility measurements show Pauli paramagnetism for YbAuCd and Curie‐Weiss behavior above 100 K for EuAuCd with an experimental magnetic moment of 7.86(6) μ_B/Eu. Ferromagnetic ordering is detected at 28 K. The saturation magnetic moment is 7.1(1) μ_B/Eu at 1.9 K. ¹⁵¹Eu Mössbauer spectra show an isomer shift of –9.2(2) mm/s and full magnetic hyperfine field splitting at 4.2 K with an internal hyperfine field of 19.5(4) T at the europium nuclei. The RE₂Au₂Cd compounds crystallize with the Mo₂FeB₂ structure, a ternary ordered version of the U₃Si₂ type. These structures may be considered as an intergrowth of distorted CsCl and AlB₂ related slabs of compositions RECd and REAu₂. Chemical bonding in REAuCd and RE₂Au₂Cd is briefly discussed.