Ternary Indides RE4Pd10In21 (RE = La,Ce, Pr,Nd, Sm) — Synthesis,Structure, and Physical Properties

The ternary indium compounds RE₄Pd₁₀In₂₁ (RE = La, Ce, Pr, Nd, Sm) were synthesized from the elements in glassy carbon crucibles in a high‐frequency furnace. Single crystals of Sm₄Pd₁₀In₂₁ were obtained from an indium flux. An arc‐melted precursor alloy of the starting composition ～SmPd₃In₆ was annealed with a slight excess of indium at 1200 K followed by slow cooling (5 K/h) to 870 K. All compounds were investigated by X‐ray powder diffraction and the structures were refined from single crystal diffractometer data. The RE₄Pd₁₀In₂₁ indides are isotypic with Ho₄Ni₁₀Ga₂₁, space group C2/m: a = 2314.3(2), b = 454.70(7), c = 1940.7(2) pm, β = 133.43(2)°, wR2 = 0.0681, 1678 F² values for La₄Pd₁₀In₂₁, a = 2308.2(1), b = 452.52(4), c = 1944.80(9) pm, β = 133.40(1)°, wR2 = 0.0659, 1684 F² values for Ce₄Pd₁₀In₂₁, a = 2303.8(2), b = 450.78(4), c = 1940.6(1) pm, β = 133.39(1)°, wR2 = 0.0513, 1648 F² values for Pr₄Pd₁₀In₂₁, a = 2300.2(2), b = 449.75(6), c = 1937.8(2) pm, β = 133.32(1)°, wR2 = 0.1086, 1506 F² values for Nd₄Pd₁₀In₂₁, and a = 2295.6(2), b = 447.07(4), c = 1935.7(1) pm, β = 133.16(1)°, wR2 = 0.2291, 2350 F² values for Sm₄Pd₁₀In₂₁, with 108 variables per refinement. All palladium atoms have a trigonal prismatic coordination. The strongest bonding interactions occur for the Pd—In and In—In contacts. The structures are composed of covalently bonded three‐dimensional [Pd₁₀In₂₁] networks in which the rare earth metal atoms fill distorted pentagonal channels. The crystal chemistry and chemical bonding in these indides is briefly discussed. Magnetic susceptibility measurements show diamagnetism for La₄Pd₁₀In₂₁ and Curie‐Weiss paramagnetism for Ce₄Pd₁₀In₂₁, Pr₄Pd₁₀In₂₁, and Nd₄Pd₁₀In₂₁. The neodymium compound orders antiferromagnetically at T_N = 4.5(2) K and undergoes a metamagnetic transition at a critical field of 1.5(2) T. All the RE₄Pd₁₀In₂₁ indides studied are metallic conductors.     

Quaternary Germanides RE3TRh4Ge4 (RE = Ce,Pr, Nd; T = Nb,Ta) – A New Coloring Variant of the Aristotype AlB2

The quaternary germanides RE₃TRh₄Ge₄ (RE = Ce, Pr, Nd; T = Nb, Ta) were synthesized from the elements by arc‐melting and subsequent annealing in a muffle furnace. The structure of Ce₃TaRh₄Ge₄ was refined from single‐crystal X‐ray diffractometer data: new type, Pbam, a = 719.9(2), b = 1495.0(3), c = 431.61(8), wR₂ = 0.0678, 1004 F² values, and 40 variables. Isotypy of the remaining phases was evident from X‐ray powder patterns. Ce₃TaRh₄Ge₄ is a new superstructure variant of the aristotype AlB₂ with an ordering of cerium and tantalum on the aluminum site, whereas the honey‐comb network is built up by a 1:1 ordering of rhodium and germanium. This crystal‐chemical relationship is discussed based on a group‐subgroup scheme. The distinctly different size of tantalum and cerium leads to a pronounced puckering of the [Rh₄Ge₄] network, which shows the shortest interatomic distances (253–271 pm Rh–Ge) within the Ce₃TaRh₄Ge₄ structure. Another remarkable structural feature concerns the tantalum coordination with six shorter Ta–Rh bonds (265–266 pm) and six longer Ta–Ge bonds (294–295 pm). The [Rh₄Ge₄] network fully separates the tantalum and cerium atoms (Ce–Ce > 387 pm, Ta–Ta > 431 pm, and Ce–Ta > 359 pm). The electronic density of states DOS from DFT calculations show metallic behavior with large contributions of localized Ce 4f as well as itinerant ones from all constituents at the Fermi level but no significant magnetic polarization on Ce could be identified. The bonding characteristics described based on overlap populations illustrate further the crystal chemistry observations of the different coordination of Ce1 and Ce2 in Ce₃TaRh₄Ge₄. The Rh–Ge interactions within the network are highlighted as dominant. The bonding magnitudes follow the interatomic distances and identify differences of Ta bonding vs. Ce1/Ce2 bonding with the Rh and Ge substructures.     

Syntheses and Structures of RE4Pt10In21 (RE = La–Nd)

The isotypic indides RE₄Pt₁₀In₂₁ (RE = La, Ce, Pr, Nd) were prepared by melting mixtures of the elements in an arc‐furnace under an argon atmosphere. Single crystals were synthesized in tantalum ampoules using special temperature modes. The four samples were studied by powder and single crystal X‐ray diffraction: Ho₄Ni₁₀Ga₂₁ type, C2/m, a = 2305.8(2), b = 451.27(4), c = 1944.9(2) pm, β = 133.18(7)°, wR2 = 0.045, 2817 F² values, 107 variables for La₄Pt₁₀In₂₁, a = 2301.0(2), b = 448.76(4), c = 1941.6(2) pm, β = 133.050(8)°, wR2 = 0.056, 3099 F² values, 107 variables for Ce₄Pt₁₀In₂₁, a = 2297.4(2), b = 447.4(4), c = 1939.7(2) pm, β = 132.95(1)°, wR2 = 0.059, 3107 F² values, 107 variables for Pr₄Pt₁₀In₂₁, and a = 2294.7(4), b = 446.1(1), c = 1938.7(3) pm, β = 132.883(9)°, wR2 = 0.067, 2775 F² values, 107 variables for Nd₄Pt₁₀In₂₁. The 8j In2 positions of all structures have been refined with a split model. The In1 sites of the lanthanum and the cerium compound show small defects, leading to the refined composition La₄Pt₁₀In_20.966(6) and Ce₄Pt₁₀In_20.909(6) for the investigated crystals. The same position shows Pt/In mixing in the praseodymium and neodymium compound leading to the refined compositions Pr₄Pt_10.084(9)In_20.916(9) and Nd₄Pt_10.050(9)In_20.950(9). All platinum atoms have a tricapped trigonal prismatic coordination by rare‐earth metal and indium atoms. The shortest interatomic distances occur for Pt–In followed by In–In. Together, the platinum and indium atoms build up three‐dimensional [Pt₁₀In₂₁] networks in which the rare earth atoms fill distorted pentagonal tubes. The crystal chemistry of RE₄Pt₁₀In₂₁ is discussed and compared with the RE₄Pd₁₀In₂₁ indides and isotypic gallides.     

Synthesis and Structures of Yb4Rh7Ge6 and Yb4Ir7Ge6

Larger single crystals of Yb₄Rh₇Ge₆ and Yb₄Ir₇Ge₆ were prepared from arc‐melted precursor alloys Rh₇Ge₆ and Ir₇Ge₆ and elemental ytterbium via the Bridgman method using tungsten crucibles. Yb₄Rh₇Ge₆ and Yb₄Ir₇Ge₆ were investigated by X‐ray diffraction on powders and single crystals. Both germanides crystallize with the cubic U₄Re₇Si₆ type structure, space group Im3m. Structure refinement from X‐ray single crystal diffractometer data yielded a = 825.3(1) pm, wR2 = 0.0292, 106 F² values, 10 variable parameters for Yb₄Rh₇Ge₆ and a = 826.6(2) pm, wR2 = 0.0486, 150 F² values, 10 variable parameters for Yb₄Ir₇Ge₆. The structures contain two crystallographically independent transition metal (T) atoms with octahedral (T1) and tetrahedral (T2) germanium coordination. The octahedra and tetrahedra are condensed via common corners and edges forming complex three‐dimensional [T₇Ge₆] networks in which the trivalent ytterbium atoms fill voids of coordination number 14.     

Rare‐Earth‐Rich Magnesium Compounds RE23Rh7Mg4 (RE = La,Ce, Pr,Nd, Sm,Gd) with Tetrahedral Mg4 Clusters

The rare earth‐rich compounds RE₂₃Rh₇Mg₄ (RE = La, Ce, Pr, Nd, Sm, Gd) were prepared by induction‐melting the elements in sealed tantalum tubes. The new compounds were characterized by X‐ray powder diffraction. They crystallize with the hexagonal Pr₂₃Ir₇Mg₄ type structure, space group P6₃mc. The structures of La₂₃Rh₇Mg₄ (a = 1019.1(1), c = 2303.7(4) pm, wR2 = 0.0827, 1979 F² values, 69 variables), Nd₂₃Rh₇Mg₄ (a = 995.4(2), c = 2242.3(5) pm, wR2 = 0.0592, 2555 F² values, 74 variables) and Gd₂₃Rh_6.86(5)Mg₄ (a = 980.5(2), c = 2205.9(5) pm, wR2 = 0.0390, 2083 F² values, 71 variables) were refined from single crystal X‐ray diffractometer data. The three crystallographically different rhodium atoms have trigonal prismatic rare earth coordination with short RE–Rh distances (283–300 pm in Nd₂₃Rh₇Mg₄). The prisms are condensed via common edges, leading to a rigid three‐dimensional network in which isolated Mg₄ tetrahedra (312–317 pm Mg–Mg in Nd₂₃Rh₇Mg₄) are embedded. Temperature dependent magnetic susceptibility data of Ce₂₃Rh₇Mg₄ indicate Curie‐Weiss behavior with an experimental magnetic moment of 2.52(1) μ_B/Ce atom, indicative for stable trivalent cerium. Antiferromagnetic ordering is evident at 2.9 K.     

Platinum‐Indium Polyanions in the Structures of LaPtIn4 and LnPtIn3 (Ln = La,Ce, Pr,Nd, Sm) and Structure Refinement of Ce2Pt2In

The title compounds were prepared by reacting the elements in an arc‐melting furnace and subsequent annealing. The LaRuSn₃ type structure of the new compounds LnPtIn₃ (Ln = La, Ce, Pr, Nd, Sm) was refined from single crystal X‐ray data for LaPtIn₃: Pm3n, a = 980.4(2) pm, wR2 = 0.0271, 399 F² values, 15 variables. Striking structural motifs of LaPtIn₃ are condensed distorted trigonal [PtIn₆] prisms with Pt–In distances of 269 pm. The lanthanum atoms occupy large cavities within the polyhedral network. Besides Pt–In bonding In–In bonding also plays an important role in LaPtIn₃ with In–In distances of 299 and 327 pm. The La1 position is occupied only to 91%, resulting in a composition La_0.98(1)PtIn₃. The La1 atoms show an extremely large displacement parameter indicating a rattling of these atoms in the In₁₂ cages. The so far most indium rich compound in the ternary system lanthanum‐platinum‐indium is LaPtIn₄ which was characterized on the basis of Guinier powder data: YNiAl₄‐type, Cmcm, a = 455.1(2) pm, b = 1687.5(5) pm, and c = 738.3(2) pm. The platinum atoms in LaPtIn₄ center trigonal prisms with the composition [La₂In₄]. Together with the indium atoms the platinum atoms form a complex three‐dimensional [PtIn₄] polyanion in which the lanthanum atoms occupy large hexagonal tubes. The structure of Ce₂Pt₂In is confirmed: Mo₂FeB₂‐type, P4/mbm, a = 779.8(1) pm, c = 388.5(1) pm, wR2 = 0.0466, 433 F² values, 12 parameters. It is built up from CsCl and AlB₂ related slabs with the compositions CeIn and CePt₂, respectively. Chemical bonding in the [PtIn₃] and [PtIn₄] polyanions of LaPtIn₃ and LaPtIn₄ is discussed.     

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.     

Trivalent‐Intermediate Valent Cerium Ordering in Ce2RuZn4

The new intermetallic cerium compound Ce₂RuZn₄ was synthesized from the elements in a sealed tantalum tube in a water‐cooled sample chamber of an induction furnace. Ce₂RuZn₄ crystallizes with a new structure type: P4/nmm, Z = 2, a = 719.6(1), c = 520.2(1) pm, wR2 = 0.0816, 273 F² values and 15 variables. The structure contains two crystallographically independent cerium atoms: Ce1 with CN 16 (12 Zn + 4 Ce) and Ce2 with CN 14 (2 Ru + 8 Zn + 4 Ce). Based on the interatomic distances the two sites can be assigned to trivalent Ce1 and intermediate valent Ce2. The trivalent‐intermediate valent cerium ordering is underlined by magnetic susceptibility measurements. Ce₂RuZn₄ shows modified Curie‐Weiss behaviour in the temperature range 10–290 K with an experimental magnetic moment of 2.57(1) μ_B per formula unit. Thus only half of the cerium atoms are trivalent in Ce₂RuZn₄. A remarkable feature of the Ce₂RuZn₄ structure are short Ce2–Ru distances of 260 pm. The crystal chemistry of Ce₂RuZn₄ is discussed.     

ChemInform Abstract: Experimental and Theoretical Investigations for Site Preference and Anisotropic Size Change of RE11Ge4In6‐xMx (RE: La,Ce; M: Li,Ge; x = 1, 1.96).

La₁₁Ge₄In_5.00Li_1.00 and Ce₁₁Ge_5.96In_4.04 are prepared from the elements (Nb tubes, 1080 °C for 5 h and 750 °C for 2 d) and characterized by powder and single crystal XRD, and TB‐LMTO‐ASA computations.     

Stabilizing the LaCoAl4 Structure through Indium‐Magnesium Substitution in CeRhIn4−xMgx (x = 0.79 and 0.84) – An Indide with Magnesium Centered Indium Cubes

The intermetallic compounds CeRhIn_4?xMg_x (x = 0.79 and 0.84) were prepared from the elements in sealed tantalum ampoules in a high‐frequency furnace. The samples were investigated by X‐ray powder and single crystal diffraction: LaCoAl₄ type, Pmma, a = 829.5(2), b = 433.56(9), c = 740.2(2) pm, wR2 = 0.0458, 651 F² values, 25 variables for CeRhIn_3.21Mg_0.79 and a = 831.44(10), b = 433.49(10), c = 741.04(10) pm, wR2 = 0.0543, 915 F² values, 25 variables for CeRhIn_3.16Mg_0.84. The indium atoms build up two‐dimensional networks perpendicular to the b axis in an AA stacking sequence leaving slightly distorted trigonal, square and pentagonal prismatic voids for the rhodium, magnesium, and cerium atoms. Both square prismatic voids show small magnesium/indium mixing. The shortest interatomic distances occur for the Rh–Mg contacts (257 pm). Together, the rhodium, indium, and magnesium atoms build up three‐dimensional [RhIn_4?xMg_x] networks in which the cerium atoms fill distorted pentagonal channels.     

Nd3Ge1.18In0.82 and Sm3Ge1.33In0.67 – New ternary indides with La3GeIn type structure

New indides, Nd₃Ge_1.18In_0.82 and Sm₃Ge_1.33In_0.67, were synthesized from the elements by arc-melting and subsequent annealing at 870 K. Single crystals were grown through special annealing procedures in sealed tantalum tubes in a resistance furnace. Both compounds were investigated on the basis of X-ray powder and single crystal data: La₃GeIn type structure, Pearson code tI80, space group I4/mcm; a = 1200.1(1), c = 1562.8(1) pm, wR2 = 0.0781, 716 F² values, 34 variables for Nd₃Ge_1.18In_0.82 and a = 1184.7(2), c = 1537.0(3) pm, wR2 = 0.0305, 911 F² values, 34 variables for Sm₃Ge_1.33In_0.67. The crystal chemistry in Nd₃Ge_1.18In_0.82 is discussed from a geometrical point of view and in terms of LMTO band structure calculations.     

New Rare‐Earth Metal Germanides RE2Ge9 (RE = Nd,Sm) by Thermal Decomposition of High‐Pressure Phases REGe5

The rare‐earth metal germanides RE₂Ge₉ (RE = Nd, Sm) have been prepared by thermal decomposition of the metastable high‐pressure phases REGe₅ at ambient pressure. The compounds adopt an orthorhombic unit cell with a = 396.34(4) pm; b = 954.05(8) pm and c = 1238.4(1) pm for Nd₂Ge₉ and a = 395.46(7) pm; b = 946.4(2) pm and c = 1232.1(3) pm for Sm₂Ge₉. Crystal structure refinements reveal space group Pmmn (No. 59) for Nd₂Ge₉. The atomic pattern resembles an ordered defect variety of the pentagermanide motif REGe₅ (RE = La; Nd, Sm, Gd, Tb) comprising corrugated germanium layers. These condense into a three‐dimensional network interconnected by eight‐coordinated germanium atoms. The resulting framework channels along [100] enclose the neodymium atoms. With respect to the atomic arrangement of the pentagermanides, half of the interlayer germanium atoms are eliminated in an ordered way so that occupied and empty germanium columns alternate along [001]. The rare‐earth metal atoms of both types of compounds, REGe₅ and RE₂Ge₉, exhibit the electronic states 4f ³ and 4f ⁵ (oxidation state +3) for neodymium and samarium, respectively, evidencing that the modification of the germanium network leaves the electron configuration of the metal atoms unaffected.     

Trivalent‐Intermediate Valent Cerium Ordering in CeRuSn – A Static Intermediate Valent Cerium Compound with a Superstructure of the CeCoAl Type

New equiatomic stannide CeRuSn was synthesized from the elements by arc‐melting. CeRuSn was investigated by X‐ray powder and single crystal diffraction: C2/m, a = 1156.1(4), b = 475.9(2) and c = 1023.3(4) pm, β = 102.89(3)°, wR2 = 0.0466, 1229 F² values and 38 variables. CeRuSn adopts a superstructure of the monoclinic CeCoAl type through a doubling of the subcell c axis. In the superstructure two crystallographically independent cerium sites occur. Based on the interatomic distances the two sites can be assigned to trivalent Ce2 and intermediate valent Ce1. This trivalent‐intermediate valent cerium ordering is underlined by magnetic susceptibility measurements χ_m(T): below 150 K χ_m, measured with decreasing temperature, follows a Curie‐Weiss law χ_m = C_m/(T–θ_p) giving C_m = 0.38 emuK/mol as Curie constant per CeRuSn mol; a value showing that only half of the cerium atoms are trivalent in CeRuSn (C_m = 0.807 emuK/mol for one free Ce³⁺ ion). A remarkable feature of the CeRuSn structure are the short Ce1–Ru1 (233 pm) and Ce1–Ru2 (246 pm) distances. The crystal chemistry of CeRuSn is discussed on the basis of a group‐subgroup scheme.     

The Structure of La3Au4In7 and its Relation to the BaAl4 Type

La₃Au₄In₇ was prepared by arc‐melting of the elements and subsequent annealing at 970 K. X‐ray diffraction of powders and single crystals yielded I2/m11, mI28, a = 460.42(5) pm, b = 1389.5(1) pm, c = 1039.6(2) pm, α = 90.77(1)°, wR2 = 0.0621, 1089 F² values, 46 variables. The structure of La₃Au₄In₇ is of a new type. It may be considered as a monoclinically distorted, ordered variant of the La₃Al₁₁ type. The structural relation with the family of BaAl₄ related compounds is discussed on the basis of a group‐subgroup scheme. The gold and indium atoms in La₃Au₄In₇ build a three‐dimensional [Au₄In₇] polyanion in which the lanthanum atoms fill distorted pentagonal and hexagonal channels. Within the polyanion short Au–In and In–In distances are indicative of strongly bonding Au–In and In–In interactions.     

Neue Germanide mit geordneter Ce3Pt4Ge6‐Struktur – Die Verbindungen Ln3Pt4Ge6 (Ln: Pr–Dy)

New Germanides with an Ordered Variant of the Ce₃Pt₄Ge₆ Type of Structure – The Compounds Ln₃Pt₄Ge₆ (Ln: Pr–Dy) Six new germanides Ln₃Pt₄Ge₆ with Ln = Pr–Dy were synthesized by heating mixtures of the elements at 900 °C, annealing the inhomogeneous powders at 1050‐1100 °C for six days and then cooling down from 700 °C in the course of two months. The crystal structures of Pr₃Pt₄Ge₆ (a = 26.131(5), b = 4.399(1), c = 8.820(2) Å), Sm₃Pt₄Ge₆ (a = 25.974(3), b = 4.356(1), c = 8.748(1) Å), and Dy₃Pt₄Ge₆ (a = 26.079(5), b = 4.311(1), c = 8.729(2) Å) were determined by single crystal X‐ray methods. The compounds are isotypic (Pnma, Z = 4) and crystallize with an ordered variant of the Ce₃Pt₄Ge₆ type of structure (Cmcm, Z = 2) consisting of CaBe₂Ge₂‐ and YIrGe₂‐analogous units. The platinum atoms are located in distorted square pyramids of germanium atoms and build up with them a three‐dimensional network. The coordination polyhedra of the platinum and germanium atoms around the rare‐earth metal atoms are pentagonal and hexagonal prisms. These are completed by some additional atoms resulting in coordination numbers of 14 and 15 respectively. The other germanides were investigated by powder methods resulting in the following lattice constants: a = 26.067(6), b = 4.388(1), c = 8.800(2) Å for Ln = Nd; a = 25.955(7), b = 4.337(1), c = 8.728(2) Å for Ln = Gd; a = 25.944(5), b = 4.322(1), c = 8.698(2) Å for Ln = Tb. The atomic arrangement of Ln₃Pt₄Ge₆ is compared with the well‐known monoclinic structure of Y₃Pt₄Ge₆.     

Bridgman Crystal Growth and Structure Refinement of YbPdGe and YbPtGe – Two Different Superstructures of the KHg2 Type

Well shaped single crystals of the equiatomic germanides YbPdGe and YbPtGe were synthesized from the elements using the Bridgman technique. The samples were investigated by X‐ray powder and single crystal diffraction: YbAuSn type, Imm2, a = 433.4(2), b = 2050.6(6), c = 752.6(2) pm, wR2 = 0.0723, 1551 F² values, 58 variables for YbPdGe and TiNiSi type, Pnma, a = 686.32(9), b = 430.47(9), c = 751.02(8) pm, wR2 = 0.0543, 379 F² values, 20 variables for YbPtGe. Both germanides crystallize with different superstructure variants of the KHg₂ type, resulting from different stacking of the puckered Pd₃Ge₃ and Pt₃Ge₃ hexagons. While only Pt–Ge interactions occur in the [PtGe] polyanionic network of YbPtGe, weak interlayer Pd–Pd (297 pm) and Ge–Ge (275 pm) interactions occur in YbPdGe. The crystal chemical peculiarities are discussed in the light of the different superstructure formed.     

Synthesis and Structures of SrAuIn and SrAuIn3

The intermetallic compounds SrAuIn and SrAuIn₃ were synthesised from the elements in sealed tantalum ampoules in a high‐frequency furnace. Both indides were studied by X‐ray powder and single crystal diffraction: TiNiSi type, Pnma, a = 772.2(4), b = 478.6(2), c = 844.0(4) pm, wR2 = 0.0474, 748 F² values, 20 variables for SrAuIn and BaNiSn₃ type, I4mm, a = 456.97(8), c = 1243.7(3) pm, wR2 = 0.0381, 397 F² values, 18 variables for SrAuIn₃. The latter reveals a small degree of Au/In disorder. Both structures consist of three‐dimensional [AuIn], respectively [AuIn₃] polyanionic networks with short Au–In distances (287–291 pm in SrAuIn and 268–284 pm in SrAuIn₃. The latter indide reveals also In–In bonding (294–323 pm). The larger voids within the polyanionic networks of both structures are filled by the strontium cations.     

Quaternary Germanides Formed in Molten Aluminum: Tb2NiAl4Ge2 and Ce2NiAl6‐xGe4‐y (x ∼ 0.24, y ∼ 1.34)

The intermetallic phases Tb₂NiAl₄Ge₂ and Ce₂NiAl_6‐xGe_4‐y (x ∼ 0.24, y ∼ 1.34) were synthesized in molten Al at temperatures below 1000 °C. Both compounds adopt the tetragonal space group I4/mmm with cell parameters of a= 4.1346(2) Å c = 19.3437(7) Å for Tb₂NiAl₄Ge₂ and a= 4.1951(9) Å and c = 26.524(7) Å for Ce₂NiAl_6‐xGe_4‐y. The Tb₂NiAl₄Ge₂ structure features NiAl₄Ge₂ layers separated by a double layer of rare earth ions. The Ce₂NiAl_6‐xGe_4‐y (x ∼ 0.24, y ∼ 1.34) structure also contains the NiAl₄Ge₂ layers along with a vacancy defect PbO‐type Al_2‐xGe_2‐y layer, and is related to the Ce₂NiGa₁₀ structure type. Ordering of vacancies cause the formation of a 3ax3b superstructure in the crystal as seen by electron diffraction experiments. Tb₂NiAl₄Ge₂ exhibits Curie‐Weiss paramagnetic behavior with an antiferromagnetic transition observed at ∼20 K. Ce₂NiAl_6‐xGe_4‐y shows a much more complex magnetic behavior possibly due to temperature induced variation in the valency of the Ce atoms.     

Syntheses and Structures of RE10Ni9+xIn20 (RE = Tb,Dy) and YbNiIn2

The ternary indides RE₁₀Ni_9+xIn₂₀ (RE = Tb, Dy) were synthesized from the elements by arc‐melting under argon and subsequent annealing. YbNiIn₂ was prepared in a sealed tantalum tube in a water‐cooled sample chamber of a high‐frequency furnace. X‐ray powder and single crystal data revealed isotypism with the tetragonal Ho₁₀Ni₉In₂₀ type structure, space group P4/nmm for the RE₁₀Ni_9+xIn₂₀ compounds: a = 1337.0(2), c = 909.5(2) pm, wR2 = 0.0527, 1795 F² values, 65 variables for RE = Tb, and a = 1333.63(7), c = 907.2(1) pm, wR2 = 0.0590, 1346 F² values, 65 variables for RE = Dy. Both indides show an additional nickel site (Ni4) with partial nickel occupancy leading to the refined compositions Tb₁₀Ni_9.34(2)In₂₀ and Dy₁₀Ni_9.32(2)In₂₀. YbNiIn₂ adopts the orthorhombic MgCuAl₂‐type structure: Cmcm, a = 430.67(9), b = 1033.0(2), c = 758.1(1) pm, wR2 = 0.0262, 424 F² values and 16 variable parameters. The crystal chemistry of the RE₁₀Ni_9+xIn₂₀ and RENiIn₂ compounds is briefly discussed.     

Semiconducting La2AuP3, the Metallic Conductor Ce2AuP3, and other Rare‐Earth Gold Phosphides Ln2AuP3 with Two Closely Related Crystal Structures

The compounds Ln₂AuP₃ were synthesized by reaction of the elemental components in evacuated silica tubes. Their crystal structures were determined from single‐crystal diffractometer data. The compounds with Ln = La, Ce, and Pr crystallize with an orthorhombic U₂NiC₃ type structure (Pnma, Z = 4). The structure refinement for Ce₂AuP₃ resulted in a = 774.14(6) pm, b = 421.11(4) pm, c = 1612.3(1) pm, R = 0.019 for 1410 structure factors and 38 variable parameters. For Pr₂AuP₃ a residual of R = 0.024 was obtained. Nd₂AuP₃ crystallizes with a monoclinic distortion of this structure: P2₁/c, Z = 4, a = 416.14(4) pm, b = 768.87(6) pm, c = 1647.1(2) pm, β = 104.06(1)°, R = 0.022 for 1361 F values and 56 variables. The near‐neighbor coordinations of the two structures are nearly the same. In both structures the gold and phosphorus atoms form two‐dimensionally infinite nets, where the gold atoms are tetrahedrally coordinated by phosphorus atoms with Au–P distances varying between 245.8 and 284.2 pm. Two thirds of the phosphorus atoms form pairs with single‐bond distances varying between 217.7 and 218.9 pm. Thus, using oxidation numbers the structures can be rationalized with the formulas (Ln⁺³)₂[AuP₃]^–6 and (Ln⁺³)₂Au⁺¹(P₂)^–4P^–3. Accordingly, La₂AuP₃ is a diamagnetic semiconductor. Pr₂AuP₃ is semiconducting with an antiferromagnetic ground state, showing metamagnetism with a critical field of B_c = 0.5(± 0.1) T. In contrast, the cerium compound is a metallic conductor, even though its cell volume indicates that the cerium atoms are essentially trivalent, as is also suggested by the ferro‐ or ferrimagnetic behavior of the compound.