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.     

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.     

The ternary rare earth ruthenium gallides R3Ru4Ga15 (R=Y, Tb-Er) with a new structure type, a further example of a recently recognized large family of structures

The title compounds were prepared by reaction of the elemental components at high temperature. They crystallize with a new orthorhombic structure type which was determined from single-crystal diffractometer data of Ho₃Ru₄Ga₁₅: Pnma, a=871.7(1) pm, b=956.4(1) pm, c=1765.9(3) pm, Z=4, R=0.040 for 1039 structure factors and 114 variable parameters. The structure may be viewed as consisting of two kinds of atomic layers, although atomic bonding within and between the layers is comparable strength, as can be judged from the near-neighbor environments, where all of the 15 atomic sites have high coordination numbers. One kind of atomic layers (A) contains all of the holmium and additional gallium atoms in the ratio Ho:Ga=3:5 with a unit mesh content of 2Ho₃Ga₅; these layers are flat. The other layers (B) consist of sheets of corner- and edge-sharing condensed RuGa₆ octahedra, which are extremely compressed resulting in a hexagonal close-packed, puckered net with a Ru:Ga ratio of 2:5 and a unit mesh content of 4Ru₂Ga₅. These nets alternate in the sequence ABAB, ABAB, thus yielding the formula 4Ho₃Ga₅·8Ru₂Ga₅=4Ho₃Ru₄Ga₁₅. Similar layers are observed in the structures of Y₂Co₃Ga₉, Gd₃Ru₄Al₁₂, Er₄Pt₉Al₂₄, CeOsGa₄, CaCr₂Al₁₀, and the four stacking variants with the compositions TbRe₂Al₁₀, DyRe₂Al₁₀, YbFe₂Al₁₀, and LuRe₂Al₁₀.     

Nd4Ti9O24: Präparation und Struktur

Preparation and Crystal Structure of Nd₄Ti₉O₂₄ The compound Nd₄Ti₉O₂₄ was prepared by heating mixtures of Nd₂O₃/TiO₂ (1 : 4.5) at temperatures of T = 1 330°C in air (2× 1d). Single crystals of Nd₄Ti₉O₂₄ were obtained by chemical transport reaction (T₂→T₁; T₁ = 1000°C, T₁ = 900°C, 14 d) using chlorine (p(Cl₂, 298 K) = 1 atm) as transport agent with Nd₄Ti₉O₂₄ as starting material. Nd₄Ti₉O₂₄ crystallizes in the orthorhombic space group Fddd (No. 70) with a = 13.9926(11) Å, b = 35.2844(21) Å, c = 14.4676(17) Å (Z = 16). The structure was refined to give R = 4.0% and R, = 3.7%. Main building units are TiO₆ octahedra, NdO₆ distorted square antiprisms and NdO₆ octahedra.     

Preparation and crystal structure of ternary rare-earth platinum metal aluminides R2T3Al9 (T=Rh, Ir, Pd) with Y2Co3Ga9-type structure and magnetic properties of the iridium compounds

The ternary aluminides R₂Rh₃Al₉ (R=Y, La-Nd, Sm, Gd-Tm, Lu), R₂Ir₃Al₉ (R=Y, La-Nd, Sm, Gd-Lu), and R₂Pd₃Al₉ (R=Y, Gd-Tm) have been prepared by arc melting of the elemental components with an excess of aluminum and dissolving the aluminum-rich matrix in hydrochloric acid. They crystallize with Y₂Co₃Ga₉-type structure: Cmcm, Z=4. The crystal structures of Ho₂Rh₃Al₉ and Er₂Ir₃Al₉ have been refined from single-crystal X-ray data; Ho₂Rh₃Al₉: a=1316.8(3) pm, b=760.2(2) pm, c=933.7(2) pm, R=0.044 for 255 structure factors and 27 variables; Er₂Ir₃Al₉: a=1313.8(2) pm, b=758.5(1) pm, c=933.8(2) pm, R=0.057 (392 F values, 27 variables). The structure may be viewed as consisting of atomic layers of the compositions A=R₂Al₃ and B=T₃Al₆ which alternate in the sequence ABAB along the z direction. Approximately 33% and 27% of the A layers were found to be misplaced in the crystals investigated for Ho₂Rh₃Al₉ and Er₂Ir₃Al₉, respectively. The magnetic properties of most iridium-containing compounds have been determined with a superconducting quantum interference device magnetometer. The yttrium and the lanthanum compounds show Pauli paramagnetism, others reflect the magnetic behavior of the rare-earth components. The magnetic ordering temperatures are all lower than 20 K.     

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 Structure of the Ternary Lanthanoid Platinum Antimonides Ln3Pt7Sb4 (Ln = Ce,Pr, Nd,and Sm) with Er3Pd7P4 Type Structure

The four compounds Ln₃Pt₇Sb₄ (Ln = Ce, Pr, Nd, and Sm) were prepared from the elements by arc‐melting and subsequent heat treatment in resistance and high‐frequency furnaces. The crystal structure of these isotypic compounds was determined from four‐circle X‐ray diffractometer data of Nd₃Pt₇Sb₄ [C2/m, a = 1644.0(2) pm, b = 429.3(1) pm, c = 1030.6(1) pm, β = 128.58(1)°, Z = 2, R = 0.032 for 698 structure factors and 46 variable parameters] and Sm₃Pt₇Sb₄ [a = 1639.5(2) pm, b = 427.1(1) pm, c = 1031.8(1) pm, β = 128.76(1)°, Z = 2, R = 0.025 for 816 F‐values and 46 variables]. The structure is isotypic with that of the homologous phosphide Er₃Pd₇P₄. In contrast to the structure of this phosphide, where the phosphorus atoms have the coordination number nine, the larger antimony atoms of Nd₃Pt₇Sb₄ obtain the coordination number ten. The structural relationships between the structures of EuNi_2—xSb₂, EuPd₂Sb₂, CeNi_2+xSb_2—x, Ce₃Pd₆Sb₅, and Nd₃Pt₇Sb₄, all closely related to the tetragonal BaAl₄ (ThCr₂Si₂) type structure, are briefly discussed emphasizing their space group relationships.     

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).     

Die Kristallstruktur von (Al0,5Ga0,5)CuOAsO4 – Kupfer zwischen planarer und geschlossener Koordination

The Crystal Structure of (Al_0,5Ga_0,5)CuOAsO₄ – Copper Intermediate between Planar and Closed Coordination Single crystals of the new oxide arsenate (Al_0.5Ga_0.5)CuOAsO₄ (monoclinic, P2₁/c, a = 734.3(2) pm, b = 1024.79(9) pm, c = 563.4(2) pm, β = 99.93(1)°, Z = 4) were obtained by reaction of Al/As/Cu/Ga-alloys with oxygen. The crystal structure was determined from four-circle diffractometer data (w2R = 0.039 for 1211 F² values and 76 parameters). The structure contains [Cu₂O₆] double squares arranged in slabs perpendicular to the a axis such that a [4 + 1]-coordination of the copper atoms by oxygen atoms results which is intermediate between square-planar and square-pyramidal. Along [100] layers of corner sharing (Al/Ga)O₄ and AsO₄ tetrahedra are alternating with buckled Cu layers.     

The Crystal Structure of ζ2‐Al3Cu4‐δ

The crystal structure of the ζ₂‐phase Al₃Cu_4‐δ was determined by means of X‐ray powder diffraction: a = 409.72(1) pm, b = 703.13(2) pm, c = 997.93(3) pm, space group Imm2, Pearson symbol oI24‐3.5, R_I = 0.0696. ζ₂‐Al₃Cu_4‐δ forms a distinctive a × √3a × 2c superstructure of a metal deficient Ni₂In‐type‐related structure. The phase is meta‐stable at ambient temperature. Between 400 °C and 450 °C it decomposes into ζ₁‐Al₃Cu₄ and η₂‐AlCu. Entropic contributions to the stability of ζ₂‐Al₃Cu_4‐δ are reflected in three statistically or partially occupied sites.     

Die Pentatelluride M2Te5 (M = Al,Ga, In): Polymorphie,Strukturbeziehungen und Homogenitätsbereiche

The Pentatellurides M₂Te₅ (M = Al, Ga, In): Polymorphism, Structural Relations, and Homogeneity Ranges The hitherto unknown crystal structure of the black solid Al₂Te₅ is solved by Rietveld refinement of X-Ray powder data: a = 1359.29(3) pm, b = 415.27(1) pm, c = 983.92(2) pm, β = 126.97(1)°, space group: C2/m (no. 12), Z = 2. In contrast to Ga₂Te₅ and In₂Te₅Al₂Te₅ is very sensitive to hydrolysis. It can formally be described as Te[AlTe_3/3Te_1/1]₂, containing layers made up of chains of cis-edge-sharing AlTe₄ tetrahedra [AlTe_3/3Te_1/1] and additional Te atoms. In₂Te₅-I and In₂Te₅-II are characterized by layers with a similar topology, Ga₂Te₅ however is different. It has no layer structure, but contains chains of trans-edge-sharing GaTe₄-tetrahedra and additional Te-atoms according to the formulation Te[GaTe_4/2]₂. It can be regarded as a variant of the TlSe type structure. From heterogeneous samples with the nominal composition In_0.5Ga_1.5Te₅ single crystals of a new stacking variant (In₂Te₅-III) of the In₂Te₅ structure type can be isolated. The composition of the crystals, determined by single crystal structure analysis, is In_0.77Ga_1.23Te₅, with a = 1613.2(3) pm, b = 424.6(1) pm, c = 1330.5(2) pm, β = 97.39(1)°, space group C2/c (Nr. 15), Z = 4. This structure type is not yet known for unsubstituted In₂Te₅. The range of homogeneity for Ga₂Te₅ with respect to the substitution of Gallium by Indium is given by Ga_2-xIn_xTe₅ (x < 0.4). Within the limits of experimental error however a substitution of Te in Ga₂Te₅ by Se cannot be detected.     

Pt2(HSO4)2(SO4)2, the First Binary Sulfate of Platinum

Red single crystals of Pt₂(HSO₄)₂(SO₄)₂ were obtained by the reaction of elemental platinum with conc. sulfuric acid at 350 °C in sealed glass ampoules. The crystal structure (monoclinic, P2₁/c, Z = 2, a = 868.6(2), b = 826.2(1), c = 921.8(2) pm, β=116.32(1)°, R_all = 0.0348) shows dumbbell shaped Pt₂⁶⁺ cations which are coordinated by four SO₄^2— and two HSO₄^— ions. Each of the sulfate ions is attached to another Pt₂⁶⁺ ion yielding layers according to equation/tex2gif-stack-1.gif[Pt₂(SO₄)_4/2(HSO₄)_2/1]. The layers are connected by hydrogen bonds with the OH group of the hydrogensulfate ion as donor and the non‐bonding oxygen atom of the sulfate ion as acceptor.     

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.     

Sulfate und Hydrogensulfate des Erbiums: Er(HSO4)3-I,Er(HSO4)3-II,Er(SO4)(HSO4) und Er2(SO4)3

Sulfates and Hydrogensulfates of Erbium: Er(HSO₄)₃-I, Er(HSO₄)₃-II, Er(SO₄)(HSO₄), and Er₂(SO₄)₃ Rod shaped light pink crystals of Er(HSO₄)₃-I (orthorhombic, Pbca, a = 1195.0(1) pm, b = 949.30(7) pm, c = 1644.3(1) pm) grow from a solution of Er₂(SO₄)₃ in conc. H₂SO₄ at 250 °C. From slightly diluted solutions (85%) which contain Na₂SO₄, brick shaped light pink crystals of Er(HSO₄)₃-II (monoclinic, P2₁/n, a = 520.00(5) pm, b = 1357.8(1) pm, c = 1233.4(1) pm, β = 92.13(1)°) were obtained at 250 °C and crystals of the same colour of Er(SO₄)(HSO₄) (monoclinic, P2₁/n, a = 545.62(6) pm, b = 1075.6(1) pm, c = 1053.1(1) pm, β = 104.58(1)°) at 60 °C. In both hydrogensulfates, Er³⁺ is surrounded by eight oxygen atoms. In Er(HSO₄)₃-I layers of HSO₄^– groups are connected only via hydrogen bridges, while Er(HSO₄)₃-II consists of a threedimensional polyhedra network. In the crystal structure of Er(SO₄)(HSO₄) Er³⁺ is sevenfold coordinated by oxygen atoms, which belong to four SO₄^2–- and three HSO₄^–-tetrahedra, respectively. The anhydrous sulfate, Er₂(SO₄)₃, cannot be prepared from H₂SO₄ solutions but crystallizes from a NaCl-melt. The coordination number of Er³⁺ in Er₂(SO₄)₃ (orthorhombic, Pbcn, a = 1270.9(1) pm, b = 913.01(7) pm, c = 921.67(7) pm) is six. The octahedral coordinationpolyhedra are connected via all vertices to the SO₄^2–-tetrahedra.     

Na2[Pr4O2]Cl9 und K2[Pr4O2]Cl9, die ersten reduzierten quaternären Praseodymchloride mit anti-SiS2-analogen [Pr4/2O]-Ketten

Na₂[Pr₄O₂]Cl₉ and K₂[Pr₄O₂]Cl₉, the First Reduced Quaternary Praseodymium Chlorides with Anti-SiS₂ Analogous [Pr_4/2O] Chains The compounds A₂[Pr₄O₂]Cl₉ (A = Na, K) are the first reduced quaternary praseodymium chlorides with anti-SiS₂ analogous [Pr_4/2O] chains. Synthesis took place in the temperature range from 900 to 600°C in silica-jacketed niobium containers from Pr metal, PrCl₃, PrOCl and NaCl (KCl) as starting materials. The X-ray structure analysis of a single crystal of Na₂[Pr₄O₂]Cl₉ (monoclinic, P2₁/m (No. 11), Z = 2, a = 812.2(2) pm, b = 1 134.1(2) pm, c = 937.6(2) pm, β = 106.51(2)°, R = 0.048, R_w = 0.037) exhibits trans-edge connected chains of [Pr_4/2O] tetrahedra running along [001] which are connected by surrounding common chloride ions forming layers parallel to (001). These layers are connected by further chloride ions to a three-dimensional network. The sodium ions surrounded by a heavily distorted octahedron of chloride ions are placed between the layers. The X-ray structure analysis of a single crystal of the otherwise isotypic K₂[Pr₄O₂]Cl₉ (monoclinic, P2₁/m (No. 11), Z = 2, a = 820.6(2) pm, b = 1 133.2(4) pm, c = 949.2(3) pm, β = 103.94(2)°, R = 0.073, R_w = 0.054) shows that potassium is coordinated by nine chloride ions.     

Darstellung und Kristallstruktur von K6[Al2O6] und Rb6[Al2O6]

Preparation of Crystal Structure of K₆[Al₂O₆] and Rb₆[Al₂O₆] Colourless single crystals of K₆[Al₂O₆] have been prepared from intimate mixtures of KAlO₂ and K₂O (550°C, 90 d). The structure determination from four-circle diffractometer data (MoKα , 742 I_o(hkl), R = 2.2%, R_w = 2.1%) confirms the space group C2/m with Z = 2; a = 698.25 pm, b = 1 103.54 pm, c = 646.49 pm, β = 102.49°. Colourless single crystals of hitherto unknown Rb₆[Al₂O₆] have been prepared from intimate mixtures of RbAlO₂ and Rb₂O (520°C, 120 d). The structure determination from four-circle diffractometer data (MoKα , 1 240 I_o(hkl)) results in the residual values R = 7.2%, R_w = 4.9%; space group C2/m; a = 725.92 pm, b = 1 143.33 pm, c = 678.06 pm, β = 104.05°; Z = 2. K₆[Al₂O₆] and Rb₆[Al₂O₆] are isostructural with K₆[Fe₂O₆]. A characteristic structure unit is the anion [Al₂O₆]^6? consisting of two edge-sharing [AlO₄] tetrahedra. Effective Coordination Numbers (ECoN), Mean Fictive Ionic Radii (MEFIR), the Madelung Part of Lattice Energy (MAPLE) and the Charge Distribution (CHARDI) are calculated and discussed.     

[M9C4O]I8 (M = Y,Ho, Er,Lu), reduzierte Selten-Erd-Iodide mit gewellten Metall-Doppelschichten und zwei verschiedenen interstitiellen Atomen

[M₉C₄O]I₈ (M = Y, Ho, Er, Lu), Reduced Rare-Earth Iodides with Waved Metal Double Layers and Two Different Interstitial Atoms [M₉C₄O]I₈ (M = Y, Ho, Er, Lu) are examples of reduced rare-earth iodides with two different interstitial atoms. The compounds were synthesized from appropriate mixtures of MI₃, M, C and M₂O₃ at 1 050°C in arc-welded tantalum containers. The X-ray structure analysis of a single crystal of [Y₉C₄O]I₈ (orthorhombic, Pmmn (Nr. 59), Z = 2, a = 2 912.7(6) pm, b = 384.17(4) pm, c = 1 080.29(9) pm, R = 0.084, R_w = 0.053) exhibits octahedrally coordinated carbon in “plane” sections besides tetrahedrally coordinated oxygen in the “bend” of waved metal double layers. These double layers are stacked alternately with waved iodine double layers along [001].     

Kondensierte Al6‐Ringe in den Subiodiden La3Al2I2 und La2Al2I

Condensed Al₆ Rings in the Subiodides La₃Al₂I₂ and La₂Al₂I The subiodides La₃Al₂I₂ and La₂Al₂I are reported. The compounds were prepared from stoichiometric mixtures of lanthanum, aluminium, and LaI₃ under Ar atmosphere in sealed Ta ampoules at 920–950 °C and 980–1000 °C, respectively. La₃Al₂I₂ crystallizes in space group C2/m with a = 19.73(2) Å, b = 4.318(1) Å, c = 12.348(9) Å and β = 121.49(3)°, La₂Al₂I in P6₃/mmc with a = 4.3718(8) Å and c = 17.605(2) Å (isotypic with Gd₂Fe₂I). Both structures are characterized by sheets of trigonal prisms formed by the La atoms centered by aluminium, the latter being arranged in Al₆ rings. These rings are connected to chains in La₃Al₂I₂ (d_{Al(2)–Al(2)} = 2.550(4) Å and 2.615(2) Å, respectively) and layers (d_Al–Al = 2.533(1) Å) in La₂Al₂I. Both compounds are metallic conductors. The electronic structure of both compounds is discussed based on band structure calculations.     

Die neuen Schichtsilicate Ba3Si6O9N4 und Eu3Si6O9N4

The New Layer‐Silicates Ba₃Si₆O₉N₄ and Eu₃Si₆O₉N₄ The new oxonitridosilicate Ba₃Si₆O₉N₄ has been synthesized in a radiofrequency furnace starting from BaCO₃, amorphous SiO₂ and Si₃N₄. The reaction temperature was at about 1370 °C. The structure of the colorless compound has been determined by single‐crystal X‐ray diffraction analysis (Ba₃Si₆O₉N₄, space group P3 (no. 143), a = 724.9(1) pm, c = 678.4(2) pm, V = 308.69(9)· 10⁶ pm³, Z = 1, R1 = 0.0309, 1312 independent reflections, 68 refined parameters). The compound is built up of corner sharing SiO₂N₂ tetrahedra forming corrugated layers between which the Ba²⁺ ions are located. Substitution of barium by europium leads to the isotypic compound Eu₃Si₆O₉N₄. Because no single‐crystals could be obtained, a Rietveld refinement of the powder diffractogram was conducted for the structure refinement (Eu₃Si₆O₉N₄, space group P3 (no. 143), a = 711.49(1) pm, c = 656.64(2) pm, V = 287.866(8) ·10⁶ pm³, R_p = 0.0379, R_F² = 0.0638). The ²⁹Si MAS‐NMR spectrum of Ba₃Si₆O₉N₄ shows two resonances at ?64.1 and ?66.0 ppm confirming two different crystallographic Si sites.     

Die isotypen Verbindungen BaRh2Si2, BaIr2Si2 und BaPt2Ga2 – eine monokline Verzerrungsvariante der CaRh2B2-Struktur

The Isotypic Compounds BaRh₂Si₂, BaIr₂Si₂, and BaPt₂Ga₂ – a Monoclinic Distortion Variant of the CaRh₂B₂ Structure The new compounds BaRh₂Si₂ (monoclinic, P2₁/c, a = 792.6(1) pm, b = 664.5(7) pm, c = 767.9(4) pm, β = 91.2(1)°, Z = 4, 2867 reflexions, 47 parameters, R = 0.024), BaIr₂Si₂ (monoclinic, P2₁/c, a = 792.47(6) pm, b = 664.28(6) pm, c = 772.22(6) pm, β = 92.181(7)°, Z = 4, 1939 reflexions, 47 parameters, R = 0.037) and BaPt₂Ga₂ (monoclinic, P2₁/c, a = 850.4(1) pm, b = 647.3(1) pm, c = 819.8(1) pm, β = 95.97(1)°, Z = 4, 1506 reflexions, 47 parameters, R = 0.038) were prepared by reaction of the elements. Their structures were determined from single crystal data. The compounds crystallize isotypically with a distortion variant of the CaRh₂B₂ type of structure.