Ca2Pd2In and Ca2Pt2In with Monoclinic HT‐Pr2Co2Al Type Structure

The metal‐rich indides Ca₂Pd₂In and Ca₂Pt₂In were synthesised from the elements in sealed tantalum ampoules in an induction furnace. Both samples were investigated by X‐ray powder and single crystal diffraction: HT‐Pr₂Co₂Al type, C2/c, a = 1017.6(5), b = 574.1(3), c = 812.7(3) pm, β = 104.54(2)°, wR2 = 0.0344, 590 F² values for Ca₂Pd₂In and a = 1004.3(3), b = 568.9(1), c = 813.1(2) pm, β = 104.25(2)°, wR2 = 0.0435, 654 F² values for Ca₂Pt₂In with 25 variables per refinement. The structure contain Pd₂ (272 pm) and Pt₂ (264 pm) dumb‐bells with a trigonal prismatic coordination for each transition metal atom. These AlB₂ related slabs are condensed via common edges. Together the palladium and indium atoms build up three‐dimensional [Pd₂In] and [Pt₂In] polyanionic networks in which the calcium atoms fill larger channels. The bonding of calcium to the network proceeds via shorter Ca–Pd and Ca–Pt contacts. Ca₂Pd₂In and Ca₂Pt₂In are Pauli paramagnets.     

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.     

Synthesis and structure of the scandium‐rich indides Sc5Ni2In4 and Sc5Rh2In4

The ternary indides Sc₅ Ni₂ In₄ and Sc₅ Rh₂ In₄ were synthesized by arc‐melting of the elements and subsequent annealing. A structural investigation by X‐ray powder and single crystal diffraction revealed: Lu₅ Ni₂ In₄ type, Pbam, a = 1716.3(2), b = 755.1(1), c = 335.22(5) pm, wR2 = 0.0721, 844 F² values for Sc₅ Ni₂ In₄, and a = 1754.3(3), b = 765.0(1), c = 332.97(6) pm, wR2 = 0.0363, 1107 F² values for Sc₅ Rh₂ In₄ with 36 variables per refinement. Both structures can be described as intergrowths of distorted AlB₂‐ and CsCl‐related slabs, where the transition metal (T) atoms have a trigonal prismatic and the indium atoms a distorted square prismatic coordination. The shortest interatomic distances occur for Sc T and T In. The crystal chemistry and chemical bonding in these intermetallics are briefly discussed. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:364–368, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20106     

Neue Ternäre Silber(II)-fluoride: Ag3IIM2IVF14 (MIV = Zr,Hf)

New Ternary Silver (II) Fluorides: Ag M F₁₄ (M^IV = Zr, Hf) Single crystals of deeply blue violet coloured fluorides Ag₃^IIM₂^IVF₁₄ (M^IV = Zr, Hf) have been obtained by heating powder samples under F₂/N₂ (1:2) at T ≈? 600°C. The isotypic compounds crystallizes monoclinic with a = 924.9, b = 668.6, c = 907.3 pm, β = 90.30° (Ag₃Hf₂F₁₄) and a = 922.5, b = 667.6, c = 906.3 pm, β = 91.30° (Ag₃Zr₂F₁₄) (Four circle diffractometer data, Philips PW 1100), spcgr. C2/m-C_2h³ (No. 12), Z = 2. There are two different sorts of Ag²⁺:Ag(1) with coordination number C.N. [Ag(1)] = 4 + 2 and Ag(2) with C.N.[Ag(2)] = 4 + 4 against F^?. Ag(1) can be substituted by Cu²⁺, Ni²⁺, Zn²⁺, Mg²⁺ (all of blue/red violet colour), Ag(2) by Ca²⁺, Cd²⁺, Hg²⁺ (bright green). From (preliminary) powder data CuAg₂Zr₂F₁₄ with a = 912.3(4), b = 661.2(2), c = 899.4(2) pm, β = 90.70° (3) is isotypic, the other compounds seems to be of closely related type of structure.     

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.     

Ag2+ in trigonal-bipyramidaler Umgebung: Neue Fluoride mit zweiwertigem Silber: AgMMF20 (MII = Cd,Ca, Hg; MIV = Zr,Hf)

Ag²⁺ in Trigonal-Bipyramidal Surrounding New Fluorides with Divalent Silver AgM M F₂₀ (M^II = Cd, Ca, Hg; M^IV = Zr, Hf) The intensively green compounds AgMMMF₂₀ (M^II = Cd, Ca, Hg; M^IV = Zr, Hf) have been obtained for the first time as single crystals and investigated by X-ray methods. They crystallize in space group P6₃/m-C_6h² (Nr. 176) with

• a = 1052.0(2) pm, c = 828.6(2) pm (AgCd₃Zr₃F₂₀),
• a = 1048.0(2) pm, c = 832.6(3) pm (AgCd₃Hf₃F₂₀),
• a = 1059.4(2) pm, c = 841.0(3) pm (AgCa₃Zr₃F₂₀),
• a = 1053.7(2) pm, c = 830.6(3) pm (AgCa₃Hf₃F₂₀),
• a = 1058.9(3) pm, c = 832.6(4) pm (AgHg₃Zr₃F₂₀),
• a = 1056.9(2) pm, c = 833.0(3) pm (AgHg₃Hf₃F₂₀), Z = 2.

     

Structure,Chemical Bonding,and Properties of Sc2Ni2In

Sc₂Ni₂In was prepared by a reaction of the elemental components in an are furnace and subsequent annealing at 1070 K. Sc₂Ni₂In is a Pauli paramagnet and a poor metallic conductor with a specific resistivity of 224 mΩcm at room temperature. Its crystal structure was refined from X-ray powder data: P4/mbm, a = 716.79(1) pm, c = 333.154(8) pm, Z = 2, R_wp = 0.040, and R_B(I) = 0.026. Sc₂Ni₂In crystallizes with a ternary ordered version of the U₃Si₂-type structure. The nickel and indium atoms occupy [NiSc₆] trigonal prisms and [InSc₈] square prisms, respectively. These structural fragments are derived from the AlB₂ and CsCl-type structures. Semi-empirical band structure calculations reveal Sc₂Ni₂In to be a nickelide, and the strongest bonding interactions are found for the Sc? Ni contacts, followed by Sc? In and Ni? In. A rigidband model suggests the existence of the isotypic phase Sc₂Ni₂Sb.     

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.     

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.     

Ternary Indides Eu2Pd2In and Eu2Pt2In

The indides Eu₂Pd₂In and Eu₂Pt₂In were synthesized from the elements in sealed tantalum tubes in an induction furnace. The samples were characterized by powder X‐ray diffraction. The structures were refined on the basis of single‐crystal X‐ray diffractometer data: HT‐Pr₂Co₂Al type, C2/c, a = 1035.7(2), b = 592.9(1), c = 823.6(2) pm, β = 104.26(1) °, wR2 = 0.026, 1075 F² values, 25 variables for Eu₂Pd₂In and a = 1017.2(2), b = 588.7(1), c = 826.5(1) pm, β = 103.76(1) °, wR2 = 0.062, 706 F² values, 25 variables for Eu₂Pt₂In. The indium atoms have four platinum (palladium) neighbors in strongly distorted tetrahedral coordination at Pt–In and Pd–In distances ranging from 273 to 275 pm. These InPd_4/2 and InPt_4/2 units are condensed via common edges to infinite InPd₂ and InPt₂ chains, which are surrounded by the europium atoms. The chains form the motif of hexagonal rod packing.     

Synthese und Struktur von Ag7M6F31 (M = Zr,Hf, Ce)

Synthesis and Structure of Ag₇M₆F₃₁ (M = Zr, Hf, Ce) Colorless single crystals of Ag₇Zr₆F₃₁ have been obtainend by heating up a mixture of AgF and ZrF₄ in a closed goldtube (T = 450 °C, t ∼ 2 d). The compound crystallizes trigonal, space group R3‐C (No. 148) with a = 1400,9(3) pm, c = 979,0(2) pm, Z = 3. Also prepared were the isotypic compounds Ag₇Hf₆F₃₁ with a = 1393,8(2) pm, c = 978,7(2) pm, and Ag₇Ce₆F₃₁ with a = 1469,8(1) pm, c = 998,5(1) pm.     

New Intermetallic Compounds Ln2Ni2Mg (Ln = Y,La–Nd,Sm, Gd–Tm) with Mo2FeB2 Structure

The title compounds were synthesized by reacting the elements in sealed tantalum tubes in a high‐frequency furnace. They crystallize with the Mo₂FeB₂ structure, a ternary ordered variant of the U₃Si₂ type, space group P4/mbm. All compounds were characterized through Guinier powder patterns and the lattice parameters were obtained from least‐squares fits. Four structures were refined from single crystal X‐ray data: a = 740.5(1) pm, c = 372.5(1) pm, wR2 = 0.0430, 247 F values, 13 variables for Y₂Ni_1.90Mg, a = 764.5(1) pm, c = 394.39(9) pm, wR2 = 0.0371, 310 F values, 12 variables for La₂Ni₂Mg, a = 754.4(1) pm, c = 385.20(9) pm, wR2 = 0.0460, 295 F values, 12 variables for Pr₂Ni₂Mg, and a = 752.53(8) pm, c = 382.33(5) pm, wR2 = 0.0183, 291 F values, and 12 variables for Nd₂Ni₂Mg. A refinement of the occupancy parameters indicated small defects on the nickel site of the yttrium compound, resulting in the composition Y₂Ni_1.90Mg for the investigated single crystal. The compounds with cerium, samarium, and gadolinium to thulium as rare earth component were characterized through their Guinier powder patterns. The cell colume of Ce₂Ni₂Mg is smaller than that of Pr₂Ni₂Mg, indicating intermediate‐valent cerium. The structures can be considered as an intergrowth of distored AlB₂ and CsCl related slabs of compositions LnNi₂ and LnMg. Chemical bonding in La₂Ni₂Mg and isotypic La₂Ni₂In is compared on the basis of extended Hückel calculations.     

Synthesis,Structure, Chemical Bonding,and Properties of CaTIn2 (T = Pd,Pt, Au)

The new compounds CaPdIn₂, CaPtIn₂, and CaAuIn₂ were prepared from the elements by reaction in glassy carbon crucibles under flowing argon. They crystallize with the MgCuAl₂ structure type (space group Cmcm), a ternary ordered version of the Re₃B type. The three crystal structures were refined from single‐crystal four‐circle diffractometer data: a = 444.35(7), b = 1038.0(1), c = 781.32(9), wR2 = 0.1352, 455 F² values for CaPdIn₂, a = 439.65(7), b = 1043.8(1), c = 781.22(8) pm, wR2 = 0.0368, 462 F² values for CaPtIn₂, and a = 456.35(5), b = 1074.8(1), c = 759.69(8) pm, wR2 = 0.0640, 763 F² values for CaAuIn₂, with Z = 4 and 16 parameters for each refinement. Structural elements of these compounds are transition metal (T) centered trigonal prisms formed by the calcium and indium atoms. The transition metal and indium atoms form three‐dimensionally infinite [TIn₂] polyanions in which the calcium atoms occupy pentagonal channels. First principles calculations of the electronic structures of these materials strongly suggest the idea of an In–In bonded three‐dimensional network. Theoretical charge density as well as COHP analyses reveal that the calcium atom in CaAuIn₂ (isotypic with NaAuIn₂) has not completely lost its two valence electrons. Magnetic susceptibility measurements of compact polycrystalline samples of CaPdIn₂, CaPtIn₂, and CaAuIn₂ indicate weak Pauli paramagnetism. The compounds are metallic conductors with room temperature values for the specific resistivities of 35 ± 10, 20 ± 10, and 25 ± 10 μ Ωcm for CaPdIn₂, CaPtIn₂, and CaAuIn₂, respectively.     

Neue Komplexe Fluoride mit Ag2+ und Pd2+: NaMIIZr2F11 (MII = Ag,Pd) und AgPdZr2F11

New Complex Fluorides with Ag²⁺ and Pd²⁺: NaM^IIZr₂F₁₁ (M^II = Ag, Pd) and AgPdZr₂F₁₁ For the first time single crystals of NaAgZr₂F₁₁, NaPdZr₂F₁₁ and AgPdZr₂F₁₁ have been obtained and investigated by X-ray methods. The isotypic compounds NaM^IIZr₂F₁₁ (M^II = Ag, Pd) crystallize triclinic, spcgr. P1 ? C (No. 2) with a = 780.9, b = 570.0, c = 583.2 pm, α = 106.1°, β = 112.2°, γ = 97.9° (NaPdZr₂F₁₁), AgPdZr₂F₁₁ is monoclinic, spcgr. C2/m? C_2h (No. 12) with a = 935.1, b = 699.1, c = 780.1 pm, β = 115.7°, Z = 2 (Four circle diffractometer data, Siemens AED 2). Their structure is closeley related to the Ag₃Hf₂F₁₄-type of structure.     

Zur Kenntnis des Systems Cs/Cu/F: Über CsCuIICuIIIF6

The System Cs/Cu/F: On CsCu^IICu^IIIF₆ ?CsCuF_3,6’? is described in literature as a darkbrown powder which is supposed to crystallize in a cubic lattice (a = 882 pm, Debyeogramms). However Guinier photographs show that ?CsCuF_3,6’? is a mixture of CsCu^IICu^IIIF₆ (black, isotypic to CsNi^IINi^IIIF₆, a = 706.7 b = 727.7, c = 1032.2 pm, Z = 4) and Cs₂CuCu^IIIF₆ (auburn, pseudocubic, a = 623.4 c = 886.4 pm, Z = 2).     

Magnesium‐Tin Substitution in NiMg2

The binary intermetallic compound NiMg₂ (own structure type) forms a pronounced solid solution NiMg_2?xSn_x. The structure of NiMg_1.85(1)Sn_0.15(1) was refined on the basis of single crystal X‐ray data: P6₄22, a = 520.16(7), c = 1326.9(1) pm, wR2 = 0.0693, 464 F² values, and 20 variables. With increasing magnesium/tin substitution, the structure type changes. Crystals with x = 0.22 and 0.40 adopt the orthorhombic CuMg₂ type: Fddd, a = 911.0(2), b = 514.6(1), c = 1777.0(4) pm, wR2 = 0.0427, 394 F² values for NiMg_1.78(1)Sn_0.22(1), and a = 909.4(1), b = 512.9(1), c = 1775.6(1) pm, wR2 = 0.0445, 307 F² values for NiMg_1.60(1)Sn_0.40(1) with 19 variables per refinement. The nickel atoms build up almost linear chains with Ni–Ni distances between 260 and 263 pm in both modifications where each nickel atom has coordination number 10 with two nickel and eight Mg/Sn neighbors. Both magnesium sites in the NiMg₂ and CuMg₂ type structures show Mg/Sn mixing. The Ni polyhedra are condensed leading to dense layers which show a different stacking sequence in both structure types. The crystal chemical peculiarities of these intermetallics are briefly discussed.     

Synthese und Struktur von RbHfF5, Rb2Zr3F12O und Rb2Hf3F12O — zwei Oxidfluoride mit zentraler trigonal‐planarer [M3O]‐Gruppe

Synthesis and Structure of RbHfF₅, Rb₂Zr₃F₁₂O and Rb₂Hf₃F₁₂O — two Oxydefluorides with Central Trigonal‐plane [M₃O] Group Colorless RbHfF₅ crystallizes isotypic with (NH₄)ZrF₅ and TlHfF₅ monoclinic, space group P2₁/c ‐ C_2h (No. 14) with a = 776.6, b = 789.6, c = 789.8 pm, and β = 120.52°. Also colorless Rb₂Zr₃F₁₂O crystallizes trigonal, space group R3¯m — D₃d (No. 166), with a = 771.9 and c = 2963.0 pm, isotypic is Rb₂Hf₃F₁₂O with a = 769.2 pm and c = 2986.1 pm. Both compounds are isotypic with Tl₂Zr₃F₁₂O.     

Gallium‐Indium Ordering in the Complex [Ni2Ga3In] Network of GdNi2Ga3In

Polycrystalline samples of the isotypic quaternary compounds RENi₂Ga₃In (RE = Y, Gd – Tm) were obtained by arc‐melting of the elements. Crystals of the gadolinium compound were found by slow cooling of an arc‐melted button of the initial composition “GdNiGa₃In”. All samples were characterized by powder X‐ray diffraction. The structure of GdNi₂Ga_2.89In_1.11 was refined from single‐crystal X‐ray diffractometer data: new type, Pnma, a = 2426.38(7), b = 418.17(2), c = 927.27(3) pm, wR₂ = 0.0430, 1610 F² values and 88 variables. Two of the six crystallographically independent gallium sites show a small degree of Ga/In mixing. The nickel atoms show tricapped trigonal prismatic coordination by gadolinium, gallium, and indium. Together, the nickel, gallium, and indium atoms build up a complex three‐dimensional [Ni₂Ga₃In]^δ– network, which leaves cages for the gadolinium atoms. The indium atoms form zigzag chains with In–In distances of 337 pm. The crystal chemical similarities of the polyhedral packing in the GdNi₂Ga₃In and La₄Pd₁₀In₂₁ structures are discussed.     

Cs2Cu3MIVF12 (MIV = Zr,Hf) – Kristallstruktur und magnetische Eigenschaften

Cs₂Cu₃M^IVF₁₂ (M^IV = Zr, Hf) – Crystal Structure and Magnetic Behaviour Colourless single crystals of Cs₂Cu₃ZrF₁₂ are obtained by heating the binary fluorides in sealed Pt-tubes under dry argon (solid state reaction, T ≈? 700°C, t ≈? 7–10 d). The compound crystallizes trigonal-rhomboedrical in the space group R3 m-D (Nr. 166); lattice parameters are a = 716.61(6) pm, c = 2 046.4(2) pm, Z = 3 (Four cycle diffractometer data, AED 2). The structure is dominated by layers of corner-sharing, Jahn-Teller-distorted [CuF₆]-Octahedra, which are connected via regular [ZrF₆]-Octahedra to stackings parallel [00.1]. Cs⁺-ions are located in the spacings of the octahedra-network. From powder data Cs₂Cu₃HfF₁₂ with a = 716.32(4) pm, c = 2 048.6(2) pm is isotypic. Both compounds show antiferromagnetic behaviour already at temperatures about 200 K.     

Cobalt Centered Trigonal RE6 Prisms and Mg4 Clusters as Basic Structural Units in RE4CoMg (RE = Y,La, Pr,Nd, Sm,Gd–Tm)

The new rare earth metal rich intermetallic compounds RE₄CoMg (RE = Y, La, Pr, Nd, Sm, Gd–Tm) were prepared via melting of the elements in sealed tantalum tubes in a water‐cooled sample chamber of a high‐frequency furnace. The compounds were investigated by X‐ray diffraction of powders and single crystals: Gd₄RhIn type, , a = 1428.38(9) pm, wR2 = 0.0638, 680 F² values, 20 variables for La₄CoMg, a = 1399.5(2) pm, wR2 = 0.0584, 589 F² values, 20 variables for Pr₄CoMg, a = 1390.2(3) pm, wR2 = 0.0513, 634 F² values, 20 variables for Nd_3.90CoMg_1.10, a = 1381.0(3) pm, wR2 = 0.0730, 618 F² values, 22 variables for Sm_3.92Co_0.93Mg_1.08, a = 1373.1(4) pm, wR2 = 0.0586, 611 F² values, 20 variables for Gd_3.92CoMg_1.08, a = 1362.1(3) pm, wR2 = 0.0576, 590 F² values, 20 variables for Tb_3.77CoMg_1.23, a = 1344.8(2) pm, wR2 = 0.0683, 511 F² values, 20 variables for Dy_3.27CoMg_1.73, and a = 1343.3(2) pm, wR2 = 0.0560, 542 F² values, 20 variables for Er_3.72CoMg_1.28. The cobalt atoms have trigonal prismatic rare earth coordination. Condensation of the CoRE₆ prisms leads to a three‐dimensional network which leaves larger voids that are filled by regular Mg₄ tetrahedra at a Mg–Mg distance of 316 pm in La₄CoMg. The magnesium atoms have twelve nearest neighbors (3 Mg + 9 RE) in icosahedral coordination. In the structures with Nd, Sm, Gd, Tb, Dy, and Er, the RE1 positions which are not involved in the trigonal prismatic network reveal some RE1/Mg mixing and the Sm_3.92Co_0.93Mg_1.08 structure shows small cobalt defects. Considering La₄CoMg as representative of all studied systems an analysis of the chemical bonding within density functional theory closely reproduces the crystal chemistry scheme and shows the role played by the valence states of the different constituents in the electronic band structure. Strong bonding interactions were observed between the lanthanum and cobalt atoms within the trigonal prismatic network.