Synthese und Kristallstrukturen der Calcium‐Iridiumsilicide Ca3Ir4Si4 und Ca2Ir2Si

Synthesis and Crystal Structures of the Calcium Iridium Silicides Ca₃Ir₄Si₄ and Ca₂Ir₂Si The new compounds Ca₃Ir₄Si₄ und Ca₂Ir₂Si were prepared by reaction of the elemental components in sealed tantalum ampoules at 1200 °C. Their structures were determined from X‐ray single crystal data. Ca₃Ir₄Si₄(cubic, space group I4¯3m, a = 7.4171(2)Å, Z = 2) crystallizes with the Na₃Pt₄Ge₄ type structure. For Ca₂Ir₂Si (monoclinic, space group C2/c, a = 9.6567(5)Å, b = 5.8252(2)Å, c = 7.3019(4)Å, β = 100.212(2)°, Z = 4) a new structure was found. Chains of edge sharing, heavily distorted SiIr₄‐tetrahedra (Ir‐Si: 2.381 and 2.414Å) are connected via short Ir—Ir‐contacts (2.640Å) to form an open Ir/Si‐framework accommodating a three‐dimensional arrangement of calcium atoms (Ca—Ca: 3.413 ‐ 3.948Å).     

Kristall‐ und elektronische Strukturen von AIr2P2 (A: Ca — Ba)

Crystal and Electronic Structures of AIr₂P₂ (A: Ca — Ba) Single crystals of CaIr₂P₂ (a = 6.610(3), c = 7.031(3)Å) were prepared by reaction of the elements in a lead flux and investigated by X‐ray methods. The compound crystallizes with the EuIr₂P₂ type (P3₂21; Z = 3) just detected in the case of SrIr₂P₂. In the structure all the P atoms and half of the Ir atoms build a three‐dimensional framework with Ca and the remaining Ir atoms in the cavities. The latter atoms form threefold screws along [001] with relatively short Ir‐Ir distances and they are connected with the framework by Ir‐P bonds. LMTO band structure calculations suggested that the compounds with Ca, Sr, and Eu should be semiconductors. For EuIr₂P₂ this was confirmed by conductivity measurements. BaIr₂P₂ (a = 3.946(1), c = 12.572(2)Å) synthesized by heating the elements at 1050 °C for a long time crystallizes with the ThCr₂Si₂ type structure (I4/mmm; Z = 2). Due to the rigid layers of IrP₄ tetrahedra and the atomic size of barium the P‐P distance between the layers with a value of 3.71Å is very long.     

Ca3Pd4Bi8: Kristall‐ und elektronische Struktur

Ca₃Pd₄Bi₈: Crystal and Electronic Structure Ca₃Pd₄Bi₈ (a = 10.814(4), b = 17.050(6), c = 4.149(4) Å) was prepared by heating the elements at 900 °C and investigated by single crystal X‐ray methods. The compound crystallizes in a new structure type (Pbam; Z = 2). Six Bi atoms form distorted trigonal prisms around the Pd atoms. The polyhedra share common corners, edges or faces building up a three dimensional Pd, Bi network, whose holes are occupied by Ca atoms. A special feature is a distorted octahedron of four Pd and two Bi atoms connected via short homonuclear bonds. The metallic behaviour of the compound derived from the bond lengths is discussed by LMTO band structure calculations.     

Untersuchungen zum ternären System V/Mo/O

Investigation on the Ternary System V/Mo/O During chemical transport reactions mixtures of pseudo-binary line of intersection V₂O₅/MoO₃ are separated into two phases, the V₂O₅-(α) phase, which MoO₃-content depends on the oxygen partial pressure during the deposition and the MoO₃ phase which contains no more than 1% (n/n) V₂O₅. Ternary compounds do not exist on the pseudo-binary line. V₉Mo₆O₄₀ is formed by the reaction of V₂O₅ and MoO₃ (3:2) under exclusion of oxygen. The compound may be chemically transported under the own oxygen coexistence pressure. It was shown by total pressure measurements of V₂O₅/MoO₃ starting mixtures that the insertion of MoO₃ in the α-phase and the formation of the V₉Mo₆O₄₀ phase respectively is connected with elimination of oxygen and the reduction of V^V to V^IV in equivalence of the quantity of incorporated MoO₃.     

BaAg2S2, ein Thioargentat im CaAl2Si2-Strukturtyp

BaAg₂S₂, a Thioargentate with the CaAl₂Si₂-Type Structure BaAg₂S₂ could be obtained as crystalline powder by the reaction of barium-bis[dicyanoargentate(I)] in a stream of hydrogensulfid at 500°C. Single crystals grew at 480°C in an evacuated glass ampoule filled with a flux of potassium thiocyanate and powdery BaAg₂S₂ as solid. BaAg₂S₂ crystallises in the trigonal CaAl₂Si₂-typ structure, a = 4.386(1) Å, c = 7.194(2) Å, space group P3 m1, Z = 1. The structure was determined from four-circle diffractometer data. The silver-sulphur distances are discussed with respect to the corresponding distances of the hitherto known alkaline earth-transition metal pnictides, also crystallizing in the CaAl₂Si₂-typ structure.     

Zur Synthese und Kristallstruktur der ternären Carbide Na2PdC2 und Na2PtC2

Syntheses and Crystal Structures of Ternary Carbides Na₂PdC₂ and Na₂PtC₂ Na₂PdC₂ and Na₂PtC₂ were synthesized by the reaction of sodium carbide with palladium and platinum respectively. The crystal structures could be solved from X-ray powder diffraction data (space group: P3 m1, Z = 1). Both compounds crystallize in a new structure type with [M(C₂)_2/2^2?] chains (M?Pd, Pt) as the characteristic structural unit. The existence of a C? C triple bond was confirmed by Raman spectroscopy.     

Syntheses, crystal and electronic structures of three new potassium cadmium(II)/zinc(II) tellurides: K2Cd2Te3, K6CdTe4 and K2ZnTe2

Three new ternary potassium(I) zinc(II) or cadmium(II) tellurides, namely, K₂Cd₂Te₃, K₆CdTe₄ and K₂ZnTe₂, were synthesized by solid-state reactions of the mixture of pure elements of K, Cd (or Zn) and Te in Nb tubes at high temperature. K₂Cd₂Te₃ belongs to a new structure type and its structure contains a novel two-dimensional [Cd₂Te₃]²⁻ layers perpendicular to the b-axis. K(5) cation is located at the center of five member rings of the 2D [Cd₂Te₃]²⁻ layer, whereas other K⁺ cations occupy the interlayer space. K₆CdTe₄ with a K₆HgS₄ type structure features a “zero-dimensional” structure composed of isolated CdTe₄ tetrahedra separated by the K⁺ ions. K₂ZnTe₂ in the K₂ZnO₂ structural type displays 1D [ZnTe₂]²⁻ anionic chains of edge sharing [ZnTe₄] tetrahedra separated by the potassium(I) ions. K₂Cd₂Te₃, K₆CdTe₄ and K₂ZnTe₂ revealed a band gap of 1.93, 2.51 and 3.0 eV, respectively.     

Neue ternäre Germanide: Die Verbindungen Ln4Zn5Ge6 (Ln: Gd,Tm, Lu)

New Ternary Germanides: The Compounds Ln ₄Zn₅Ge₆ ( Ln : Gd, Tm, Lu) Three new ternary germanides were prepared by heating mixtures of the elements. Gd₄Zn₅Ge₆ (a = 4.249(3), b = 18.663(17), c = 15.423(6) Å), Tm₄Zn₅Ge₆ (a = 4.190(1), b = 18.410(5), c = 15.105(5) Å), and Lu₄Zn₅Ge₆ (a = 4.179(1), b = 18.368(4), c = 15.050(3) Å) are isotypic and crystallize in a new structure type (Cmc2₁; Z = 4), composed of edge‐ and corner‐sharing ZnGe₄ tetrahedra. The rare‐earth atoms fill channels of the Zn,Ge network running along the a axis and predominantly have an octahedral coordination of Ge atoms or a pentagonal prismatic environment of Zn and Ge atoms. The ZnGe₄ tetrahedra are orientated to each other so that two of six Ge atoms form pairs, while the other ones have no homonuclear contacts. This is in accord with an ionic splitting of the formula: (Ln³⁺)₄(Zn²⁺)₅(Ge^3–)₂(Ge^4–)₄. LMTO band structure calculations support the interpretation of bondings derived from interatomic distances. The metallic conductivity of these compounds expected from the electronic band structure was confirmed by measurements of the electrical resistance of Tm₄Zn₅Ge₆.     

Darstellung und Kristallstrukturen von Ln2Al3Si2 und Ln2AlSi2 (Ln: Y,Tb–Lu)

Synthesis and Crystal Structures of Ln ₂Al₃Si₂ and Ln ₂AlSi₂ ( Ln : Y, Tb–Lu) Eight new ternary aluminium silicides were prepared by heating mixtures of the elements and investigated by means of single‐crystal X‐ray methods. Tb₂Al₃Si₂ (a = 10.197(2), b = 4.045(1), c = 6.614(2) Å, β = 101.11(2)°) and Dy₂Al₃Si₂ (a = 10.144(6), b = 4.028(3), c = 6.580(6) Å, β = 101.04(6)°) crystallize in the Y₂Al₃Si₂ type structure, which contains wavy layers of Al and Si atoms linked together by additional Al atoms and linear Si–Al–Si bonds. Through this there are channels along [010], which are filled by Tb and Dy atoms respectively. The silicides Ln₂AlSi₂ with Ln = Y (a = 8.663(2), b = 5.748(1), c = 4.050(1) Å), Ho (a = 8.578(2), b = 5.732(1), c = 4.022(1) Å), Er (a = 8.529(2), b = 5.719(2), c = 4.011(1) Å), Tm (a = 8.454(5), b = 5.737(2), c = 3.984(2) Å) and Lu (a = 8.416(2), b = 5.662(2), c = 4.001(1) Å) crystallize in the W₂CoB₂ type structure (Immm; Z = 2), whereas the structure of Yb₂AlSi₂ (a = 6.765(2), c = 4.226(1) Å; P4/mbm; Z = 2) corresponds to a ternary variant of the U₃Si₂ type structure. In all compounds the Si atoms are coordinated by trigonal prisms of metal atoms, which are connected by common faces so that Si₂ pairs (d_Si–Si: 2.37–2.42 Å) are formed.     

Synthese,Struktur und Thermolyse der ternären Ammoniumnitrate (NH4)3[M2(NO3)(9] (M  La?Gd)

Synthesis, Structure, and Thermolysis of the (NH₄)₃[M₂(NO₃)₉] (M ? La? Gd) The ternary ammonium nitrates (NH₄)₃[M₂(NO₃)₉] (M ? La-Gd) are obtained as single crystals from a solution of the respective sesquioxides in a melt of NH₄NO₃ and sublimation of the excess NH₄NO₃. In the crystal structure of (NH₄)₃[Pr₂(NO₃)₉] (cubic, P4₃32, Z = 4, a = 1 377.0(1) pm, R = 0.038, R_w = 0.023) Pr³⁺ is surrounded by six bidentate nitrate ligands of which three are bridging to neighbouring Pr³⁺ ions. This results in a branched folded chain, held together by the NH₄⁺ ions which occupy cavities in the structure. (NH₄)₃[Pr₂(NO₃)₉] is the first intermediate product of the thermal decomposition of (NH₄)₂[Pr(NO₃)₅(H₂O)₂] · 2H₂O.     

Binäre Lanthan‐Stannide mit Sn:La‐Verhältnissen nahe 1:1 – Synthesen,Kristallstrukturen, Chemische Bindung

Four binary lanthanum stannides close to the 1:1 ratio of Sn:La were synthesized from mixtures of the elements. The structures of the compounds have been determined by means of single‐crystal X‐ray data. The low temperature (α) form of LaSn (CrB‐type, orthorhombic, space group Cmcm, a = 476.33(6), b = 1191.1(2), c = 440.89(6) pm, Z = 4, R1 = 0.0247), crystallizes with the CrB‐type. The structure exhibits planar tin zigzag chains with a Sn–Sn bond length of 299.1 pm. In contrast to the electron precise Zintl compounds of the alkaline earth elements, additional La–Sn bonding contributions become apparent from the results of band structure calculations. In the somewhat tin‐richer region, the new compound La₃Sn₄ (orthorhombic, space group Cmcm, a = 451.45(4), b = 1190.44(9), c = 1583.8(2) pm, Z = 4, R1 = 0.0674), crystallizing with the Er₃Ge₄ structure type, exhibits Sn₃ segments of the zigzag chains of α‐LaSn together with a further Sn atom in a square planar Sn coordination with increased Sn–Sn bond lengths. In the Lanthanum‐richer region, La₁₁Sn₁₀ (tetragonal, space group I4/mmm, a = 1208.98(5), c = 1816.60(9) pm, Z = 4, R1 = 0.0325) forms the undistorted tetragonal Ho₁₁Ge₁₀ structure type. Its structure, which contains isolated Sn atoms, [Sn₂] dumbbells and planar [Sn₄] rings is related to the high temperature (β) form of LaSn. The structure of β‐LaSn (space group Cmmm, a = 1766.97(6), b = 1768.28(5), c = 1194.32(3) pm, Z = 60, R1 = 0.0453), which forms a singular structure type, can be derived from that of La₁₁Sn₁₀ by the removal of thin slabs. Due to the different stacking of the remaining layers, planar [Sn₄] chain segments and linear [Sn–Sn–Sn] anions are formed as additional structural elements. The chemical bonding (Sn–Sn covalent bonding, Sn–La contributions) is discussed on the basis of the simple Zintl concept and the results of FP‐LAPW calculations (density of states, band structure, valence electron densities and electron localization function).     

RbSb2 – Eine mit KSb2 verwandte Zintl‐Phase

RbSb₂ – A Zintl Phase related to KSb₂ The electron‐precise Zintl compound RbSb₂, which was known to melt incongruently at 418 °C, has been prepared in pure phase from elemental rubidium and antimony in sealed tantalum crucibles. In accordance with the ribbon‐shaped antimonide anions, the compound crystallizes with extremely thin intergrown, mechanically and chemically very sensitive needles of dark‐metallic lustre. The crystal structure could be determined and refined using single crystal x‐ray data (monoclinic, space group C2/m, a = 1403(2), b = 414.0(4), c = 855.7(14) pm, β = 104.45(12)°, Z = 4, R1 = 0.0901) despite the poor quality of the crystals. It shows fused six‐membered rings of two‐ and three‐bonded Sb atoms forming ribbons running along the monoclinic b axis, which can be interpreted as sections of the elemental structure of antimony (d_Sb‐Sb = 281.9(5) and 286.0(9) pm respectively). The structure of RbSb₂ is thus closely related to that of KSb₂, which exhibits identical antimony anions. Compared to the potassium compound, the ribbons are reoriented against each so that the coordination number of the A counter ions is increased from 6 + 2 (for A = K) to 8 + 2 (for A = Rb). The results of a FP‐LAPW band structure calculation of RbSb₂ are used to explain the chemical bonding in this classical Zintl phase with a calculated indirect band gap of 0.38 eV.     

Über Alkaliselenobismutate(III), mit einer Bemerkung zum Th3P4-Typ

About Alkali Seleno Bismuthates (III), with a Comment Regarding the Th₃P₄ Structure Type The synthesis and X-ray single crystal structure determination of the ternary selenides Rb₃BiSe₃, Cs₃BiSe₃, and RbK₂BiSe₃ are described. The compounds were synthesized via a reaction of Bi₂O₃ with the alkali carbonate in a selencharged hydrogen stream at 850°C. They crystallize in the Na₃AsS₃ structure type (space group P2₁3). In the discussion of the structure, the aristotypic Th₃P₄ structure is included.     

Kristallstrukturen und spektroskopische Untersuchungen ternärer CuII-Komplexe mit bicyclischen Dicarbonsäuren und N,N-Donor-Liganden

Crystal Structures and Spectroscopic Investigations of Ternary Cu^II-Complexes with Bicyclic Dicarboxylic Acids and N,N-Donor Ligands The synthesis of coordination compounds [CuLdam] · 3H₂O (H₂L = 7-oxa-bicyclo[2.2.1]heptane-2-exo,3-cis-dicarboxylic acid ( 1 ) and its 1-methyl-derivative ( 2 ); dam = ethylendiamine, 1,2- and 1,3-propylendiamine, 2,2′-dipyridyl, 1,10-phenanthroline) has been described. Results of visible and IR spectroscopy and magnetic data are given. In the result of X-ray analyses of [CuL¹dipy] · 3H₂O ( 1 d ) and [CuL²en] · 3H₂O ( 2 a ) the dicarboxylate anions of 1 and 2 proved to be tridentate chelating ligands. In 1 d the Cu atom has an approximately square-pyramidal coordination with the bridging O atom in the apical position. In 2 a , however, the coordination number is extended to six by an O atom of a second [CuL²en] unit resulting in a centrosymmetric complex dimer with octahedrally coordinated Cu atoms. The water molecules do not participate in the coordination of the Cu atoms and form a complicated system of hydrogen bonds in the crystal.     

Ba8Cu16P30 – eine neue ternäre Variante des Clathrat I-Strukturtyps

Ba₈Cu₁₆P₃₀ – a New Ternary Variant of the Clathrate I Type Structure Ba₈Cu₁₆P₃₀ (a = 14.117(1) Å, b = 10.093(1) Å, c = 28.022(2) Å) was prepared by heating a mixture of the elements (800°C; excess of Ba and P; removal of the by-products by acetic acid/H₂O₂). The compound crystallizes orthorhombically (Pbcn; Z = 4) in a new superstructure of the cubic clathrate I type structure with an ordered distribution of the atoms. The structure is characterized by a three-dimensional framework of CuP₄ tetrahedra with cavities in the form of pentagonal dodecahedra and tetrakaidecahedra, which are occupied by the Ba atoms. The compound shows semiconduction, therefore the composition should be Ba₈Cu_15.5P_30.5.     

New ternary rare-earth metal boride carbides R15B4C14 (R=Y, Gd-Lu) containing BC2 units: Crystal and electronic structures, magnetic properties

The ternary rare-earth boride carbides R₁₅B₄C₁₄ (R=Y, Gd-Lu) were prepared from the elements by arc-melting followed by annealing in silica tubes at 1270 K for 1 month. The crystal structures of Tb₁₅B₄C₁₄ and Er₁₅B₄C₁₄ were determined from single crystal X-ray diffraction data. They crystallize in a new structure type in space group P4/mnc (Tb₁₅B₄C₁₄: a=8.1251(5) Å, c=15.861(1) Å, Z=2, R₁=0.041 (wR₂=0.088) for 1023 reflections with I_o>2σ(I_o); Er₁₅B₄C₁₄: a=7.932(1) Å, c=15.685(2) Å, Z=2, R₁=0.037 (wR₂=0.094) for 1022 reflections with I_o>2σ(I_o)). The crystal structure contains discrete carbon atoms and bent CBC units in octahedra and distorted bicapped square antiprisms, respectively. In both structures the same type of disorder exists. One R atom position needs to be refined as split atom position with a ratio 9:1 indicative of a 10% substitution of the neighboring C⁴⁻ by C₂⁴⁻. The actual composition has then to be described as R₁₅B₄C_14.2. The isoelectronic substitution does not change the electron partition of R₁₅B₄C₁₄ which can be written as (R³⁺)₁₅(C⁴⁻)₆(CBC⁵⁻)₄•e⁻. The electronic structure was studied with the extended Hückel method. The investigated compounds Tb₁₅B₄C₁₄, Dy₁₅B₄C₁₄ and Er₁₅B₄C₁₄ are hard ferromagnets with Curie temperatures T_C=145, 120 and 50 K, respectively. The coercive field B_C=3.15 T for Dy₁₅B₄C₁₄ is quite remarkable.     

Thermochemische Untersuchungen zum quasibinären System YbOCl/SeO2

Thermochemical Investigations on the Pseudobinary System YbOCl/SeO₂ On the pseudobinary section YbOCl/SeO₂ four thermodynamically stable compounds exist in accordance with the thermal decomposition and the phase analysis of defined powder mixtures: YbOCl · 3 SeO₂ = YbSe₃O₇Cl, YbOCl · 2 SeO₂ = YbSe₂O₅Cl and YbOCl · SeO₂ = YbSeO₃Cl as well as the YbOCl‐rich phase Yb₂SeO₄Cl₂ (2 YbOCl · SeO₂). The phase barogram and the phase diagram of the pseudobinary section YbOCl/SeO₂ were set up by total pressure measurements and DTA. From the temperature dependence of the decomposition pressures the enthalpies of formation and the standard entropies of the phases were deduced. In addition, the enthalpies of formation of the new compounds were determined from the enthalpies of solution of YbOCl, SeO₂ and the quaternary phases.     

Struktur‐ und magnetochemische Untersuchungen an den ternären Phosphaten Ba2MII(PO4)2 (MII = Mn,Co) und Strukturverfeinerung von BaNi2(PO4)2

Structural and Magnetochemical Studies at the Ternary Phosphates Ba₂M^II(PO₄)₂ (M^II = Mn, Co) and Refinement of the Crystal Structure of BaNi₂(PO₄)₂ Single crystals of the following phosphates were grown by the floating zone technique using a mirror furnace and their crystal structures refined (0,02 < R₁ < 0,04 and 0,04 < wR₂ < 0,10, resp.): Ba₂Mn(PO₄)₂ (a = 531.1(1), b = 896.8(1), c = 1625.6(3) pm, β = 90.26(1)°), Ba₂Co(PO₄)₂ (a = 529.8(1), b = 884.4(1), c = 1614.4(3) pm, β = 90.68(2)°) and BaNi₂(PO₄)₂ (a = 480.0(1), c = 2327.3(5) pm, Z = 3, space group R3). Both compounds Ba₂M^II(PO₄)₂ crystallize with Z = 4 in space group P2₁/n of the monoclinic Ba₂Ni(PO₄)₂ type; BaNi₂(PO₄)₂ has the hexagonal‐rhombohedral structure of the BaNi₂(AsO₄)₂ type. Magnetic measurements of powders of Ba₂Mn(PO₄)₂ and Ba₂Co(PO₄)₂ yielded room temperature moments of μ_eff = 5,73 and 4,93 μ_B, resp., but only the manganese compound obeys the Curie‐Weiss law down to low temperatures. Weak antiferromagnetic interactions at both compounds only near T_M ≈ 5 K lead to a reciprocal susceptibility minimum.     

Ternäre Palladiumpnictide der Erdalkali- und Seltenen Erdmetalle mit ThCr2Si2- und CaBe2Ge2-Struktur

Fifteen compounds of compositionMPd₂ Pn ₂ (M = alkaline earth or rare earth metal,Pn = As, Sb, Bi) were prepared. TheirGuinier powder patterns show that the arsenides crystallize with the ThCr₂Si₂ type structure, the bismuthides with the closely related CaBe₂Ge₂ type structure. The antimonides most likely also have the CaBe₂Ge₂ structure as is demonstrated by a structure refinement of EuPd₂Sb₂ from single crystal X ray data (R = 0.039 for 366 independent structure factors and 15 variable parameters). The structure of SrPd₂As₂ (ThCr₂Si₂ type) was refined to a residual ofR = 0.020 for 182F values and 9 variables. EuPd₂Sb₂ is paramagnetic and a metallic conductor. A comparison of the cell volumes suggests intermediate valency for Eu in EuPd₂As₂.Chemical bonding and especially the reasons for the adoption of the ThCr₂Si₂ or CaBe₂Ge₂ type structures by these compounds are discussed. It is suggested that in going from the phosphides to the bismuthides the ThCr₂Si₂ structure is loosing and the CaBe₂Ge₂ structure is gaining stability due to decreasing Pd-Pd bonding and increasing Pd-pnictogen bonding. This trend is caused by the increasing size of the pnictogen component.

     

Synthese und Struktur des ersten ternären Blei(II)-Oxocuprats(I): PbCu2O2

Synthesis and Structure of the First Ternary Lead(II) Copper(I) Oxide: PbCu₂O₂ PbCu₂O₂ can be prepared by solid state reaction or by precipitation from a basic aqueous solution. Single crystals of the new compound were prepared by recrystallisation from a molten mixture (PbO? Cu₂O) and investigated by X-ray diffractometer technique. PbCu₂O₂ crystallizes isotypically with the homologue silver compound PbAg₂O₂ (monoclinic with a = 8.22₃ Å, b = 8.28₉ Å, c = 6.01₅ Å, β = 132.6₂°, Z = 4, space group C? C 1 2/c 1). The crystallographic data from the X-ray investigation are reported. The structure is built by endless [PbO_4/4]- and [CuO_2/4]-chains. Pb²⁺ has a one-sided asymmetric coordination with four next oxygen neighbours and Cu⁺ forms a stretched dumbbell with two oxygen atoms.