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.     

Wasserfreie Sulfate der Selten‐Erd‐Elemente: Synthese und Kristallstruktur von Y2(SO4)3 und Sc2(SO4)3

Anhydrous Sulfates of Rare Earth Elements: Syntheses and Crystal Structures of Y₂(SO₄)₃ and Sc₂(SO₄)₃ The reaction of YCl₃ and Li₂SO₄ in sealed gold ampoules yields colorless single crystals of Y₂(SO₄)₃. According to the X‐ray single crystal determination the compound crystallizes with orthorhombic symmetry (Pbcn, Z = 4, a = 1273.97(13), b = 916.76(9), c = 926.08(7) pm, R_all = 0.0274). The crystal structure is buildt up from [YO₆] octahedra and sulfate tetrahedra connected via all vertices. In the same way [ScO₆] octahedra and sulfate groups are connected in the crystal structure of Sc₂(SO₄)₃ (trigonal, R‐3, Z = 6, a = 870.7(1), c = 2247.0(4) pm, R_all = 0.0255). Single crystals of Sc₂(SO₄)₃ were obtained via crystallisation of powder samples from a NaCl melt. The crystal structures of both compounds are closely related to each other and to the binary sulfides Rh₂S₃ and Lu₂S₃; the structures are the same with the complex SO₄^2– ions replacing the S^2– ions of the sulfides.     

Eine Strukturvariante zum NaErCl4/α-NiWO4-Typ für ternäre Selten-Erd-Chloride vom Typ NaMCl4: Synthese und Kristallstruktur von NaLuCl4

A Structural Variant to the NaErCl₄/α-NiWO₄ Type for Ternary Rare-Earth Halides NaMCl₄: Synthesis and Crystal Structure of NaLuCl₄ Single crystals of NaLuCl₄ (orthorhombic, Pbcn (Nr. 60), Z = 4, a = 618.6(1) pm, b = 1 592.2(2) pm, c = 657.0(1) pm) were grown for the first time from the binary components using the Bridgman technique. The crystal structure may be derived from a hexagonally closest packing of Cl^? spheres with one half of all octahedral sites occupied by the cations Na⁺ and Lu³⁺, respectively. The close relation of the structure to that of NaErCl₄ (α-NiWO₄) is discussed. NaScCl₄ was found to be isotypic to NaLuCl₄.     

Discrete Pr6Pd Octahedra in Pr6Pd13Cd4 – An Intermetallic Analogon to the Subnitride Na16Ba6N

The new intermetallic compound Pr₆Pd₁₃Cd₄ was synthesized from the elements in a sealed tantalum ampoule in an induction furnace. Pr₆Pd₁₃Cd₄ was investigated by X‐ray powder and single crystal diffraction: Na₁₆Ba₆N type, , a = 975.6(1) pm, wR2 = 0.0192, 162 F² values and 12 variables. The striking motif of the Pr₆Pd₁₃Cd₄ structure are discrete palladium centred Pr₆ octahedra (296 pm Pr–Pd1) in bcc packing. The octahedra are embedded by a three‐dimensional [Pd₃Cd] network with short Pd–Pd (282 pm) and Pd–Cd (274 pm) distances. The structural similarities with the subnitrides Na₁₆Ba₆N and Ag₁₆Ca₆N are discussed.     

New Phosphides La5Zn2−xP6 and Ce5Zn2−xP6 – the n = 4 Members of the REZn2P2·n(REP) Series

The new phosphides La₅Zn_2?xP₆ and Ce₅Zn_2?xP₆ were synthesized from the rare earth metals, LaZn and CeZn precursor compounds, Zn, and red phosphorous in NaCl/KCl salt fluxes. They crystallize with a new rhombohedral structure type: , Z = 3, a = 422.11(6), c = 6220(1) pm, wR2 = 0.0369, 356 F² values, 23 variables for La₅Zn_1.69P₆ and a = 417.05(6), c = 6162(1), wR2 = 0.0343, 286 F² values, 23 variables for Ce₅Zn_1.75P₆. The P^3? phosphide anions show an h²c⁴ stacking sequence in which the RE³⁺ and Zn²⁺ cations fill 5/6 and 1/6 of the octahedral and tetrahedral voids in an ordered manner, respectively, leading to a layer of condensed ZnP₄ tetrahedra and quintupled layers of condensed REP₆ octahedra. The structures of La₅Zn_2?xP₆ and Ce₅Zn_2?xP₆ belong to a larger family of phosphides which are intergrowth variants of CaAl₂Si₂ and NaCl related slabs according to REZn₂P₂·n(REP) with n = 4 for the present phosphides.     

SYNTHESIS AND STRUCTURE OF A NEW TYPE OF COORDINA-TION COMPOUND OF Gd(Ⅲ) WITH H_2 CCH_2CH_2C(~+NH_2)C-HCOO-

<正> The crystal structure of gadolinium L-proline (Pro) complex [Gd2-(C5H9NO2)6 (H2O)6] (ClO4)6 has been determined. The complex crystallizes in the triclinic space group PI with following crystal data: a = 9. 906(3), b=13. 052(5), c = 13.703(5) A. α=109. 63(3), β=110.31(2), γ=100. 73(3)°, V=1470.3(9) A3.Mr=1710. 1, F(000) = 854,μ=26. 30 cm-1, Dc = 1. 931 g/cm3, Z=1.The structure was refined to the final R of 0. 048 for 3804 reflections. The structure is of one-dimensional chain, in which each gadolinium ion lies at the center of a distorted square antiprism of the eight oxygen atoms provided by four bridging carboxylate groups from four Pro ligands, a terminal carboxylate group from one terminal Pro ligand and three water molecules and the two neighbouring gadolinium ions are linked to each other through the two bridging carboxylate groups from the two Pro ligands. The prolines exist in the form of H2 CCH2CH2(+NH2)CHCOO-, and the complexions in the crystal are linked together by the net of hydrogen bo     

CaRhIn with TiNiSi Type Structure and CaTIn2 (T = Rh,Ir) with a New Filled Version of the Zintl Phase CaIn2

CaRhIn, CaRhIn₂, and CaIrIn₂ were synthesized by reacting the elements in glassy carbon crucibles under an argon atmosphere in a high‐frequency furnace. CaRhIn adopts the TiNiSi structure: Pnma, a = 730.0(4) pm, b = 433.1(2) pm, c = 828.8(4) pm, wR2 = 0.0707, 630 F² values, 20 variables. The CaRhIn structure consists of strongly puckered Rh₃In₃ hexagons with Rh–In distances ranging from 273 to 276 pm. Due to the strong puckering each rhodium atom has a distorted tetrahedral indium environment. The calcium atoms fill the channels within the three‐dimensional [RhIn] polyanion. CaRhIn₂ and CaIrIn₂ crystallize with a new structure type: Pnma, a = 1586.2(3) pm, b = 781.4(2) pm, c = 570.9(1) pm, wR2 = 0.0385, 1699 F² values, 44 variables for CaRhIn₂, and Pnma, a = 1588.7(3) pm, b = 780.8(1) pm, c = 574.0(1) pm, wR2 = 0.0475, 1661 F² values, 44 variables for CaIrIn₂. The structures of CaRhIn₂ and CaIrIn₂ can be described as an orthorhombically distorted rhodium respectively iridium filled CaIn₂. The motif of transition metal filling is similar to that found in MgCuAl₂ type compounds CaTIn₂ (T = Pd, Pt, Au) and SrTIn₂ (T = Rh, Pd, Ir, Pt), but constitute a different tiling. Semi‐empirical band structure calculations for CaRhIn and CaRhIn₂ reveal strong bonding In–In and Rh–In but weaker Ca–Rh and Ca–In interactions. Magnetic susceptibility and resistivity measurements of compact polycrystalline samples of CaRhIn₂ indicate weak Pauli paramagnetism and metallic conductivity with a room temperature value for the specific resistivity of 230 ± 50 μΩcm.     

Crystallochemistry of the novel two-layer RECuMg4 (RE=La, Tb) ternary compounds

The crystal structures of the new ternary compounds LaCuMg₄ and TbCuMg₄ were studied by X-ray powder diffraction and single-crystal methods, respectively. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS) was used for examining microstructure and phase composition. LaCuMg₄ crystallizes in the UCoAl₄ structure type (space group P6¯2m, Pearson code hP18, a=1.03911(1), c=0.45126(1) nm, Z=3, R_F=0.0654), while TbCuMg₄ exhibits a new structure (space group Cmmm, Pearson code oS48, a=1.35797(6), b=2.03333(9), c=0.39149(2) nm, Z=8, wR₂=0.0426). Both structures represent a family of two-layer compounds. All interatomic distances indicate metallic type bonding. The structural peculiarities of these compounds and their relations are discussed.     

Ternary Rare Earth (R) Transition Metal Aluminides R3T4Al12 (T = Ru and Os) with Gd3Ru4Al12 Type Structure

The isotypic intermetallic compounds R₃Ru₄Al₁₂ (R = Y, Pr, Nd, Sm, Gd—Tm) and R₃Os₄Al₁₂ (R = Y, Ce—Nd, Sm, Gd—Tm) were prepared by reaction of the elemental components in an arc‐melting furnace. Their crystal structure was determined from four‐circle X‐ray diffractometer data of Y₃Ru₄Al₁₂: P6₃/mmc, a = 877.7(1) pm, c = 952.3(1) pm, Z = 2, R = 0.028 for 361 structure factors and 28 variable parameters. It was also refined for Nd₃Os₄Al₁₂ (a = 889.2(1) pm, c = 960.3(1) pm, R = 0.021 for 425 F values and 30 variables) and Gd₃Os₄Al₁₂ (a = 884.7(1) pm, c = 955.3(2) pm, R = 0.020; 427 F values, 30 variables). The refinements of the occupancy parameters revealed mixed T/Al occupancy for some of the aluminum sites resulting in the compositions Y₃Ru_4.060(3)Al_11.940(3), Nd₃Os_4.43(1)Al_11.57(1), and Gd₃Os_4.44(1) Al_11.56(1), respectively. The structure is related to those found for Y₂Co₃Ga₉, Er₄Pt₉Al₂₄, CeOsGa₄, Ho₃Ru₄Ga₁₅, YbFe₂Al₁₀, TbRe₂Al₁₀, LuRe₂Al₁₀, and CaCr₂Al₁₀. Topologically all of these structures may be viewed as consisting of atomic layers, although chemical bonding within and between the layers is of similar character. Two kinds of layers can be distinguished in these structures. One kind contains all of the rare earth (occasionally also alkaline earth) and in addition aluminum or gallium atoms. The other kind of layers consists of the transition metal atoms and again aluminum or gallium atoms. These latter layers are hexa gonally close packed and slightly puckered. The three different structures of the disilicides TiSi₂, CrSi₂, and MoSi₂ also contain these layers; however, in the disilicides these layers are flat.     

Segregation of Cd2 Pairs in CaCu9Cd2 and EuCu9Cd2

The copper‐rich intermetallics CaCu₉Cd₂ and EuCu₉Cd₂ were synthesized from the elements in sealed tantalum tubes in a high‐frequency furnace. Both compounds were characterized by X‐ray powder and single crystal diffraction: Ce(Mn_0.55Ni_0.45)₁₁ type, P4/mbm, a = 844.2(1), c = 504.72(8) pm, wR2 = 0.0216, 345 F² values, 23 variables for CaCu₉Cd₂ and a = 844.1(2), c = 505.5(1) pm, wR2 = 0.0200, 331 F² values, 24 variables for EuCu_9.14Cd_1.86. The europium‐based crystal showed a small mixed Cu/Cd occupancy on the 4g site. The calcium (europium) atoms have the high coordination number 20 (16Cu + 4Cd). These polyhedra are condensed via common Cu₄ squares along the c axis. Other striking structural motifs are segregated Cd₂ pairs (291 pm in CaCu₉Cd₂) in copper coordination and slightly distorted Cu2@Cu₈Cd₄ icosahedra. The latter are connected via common Cd₂ pairs along c and form the motif of tetragonal rod packing. EuCu₉Cd₂ shows paramagnetic behavior above 100 K with an experimental magnetic moment of 7.82(1) μ_B/Eu atom, indicating purely divalent europium.