Die Undecaarsenide A3As11 (A = Rb,Cs) — Synthesen und Kristallstrukturen

Alkaline Metal Arsenides A₃As₁₁ (A = Rb, Cs): Preparation and Crystal Structures Rb₃As₁₁ and Cs₃As₁₁ were synthesized from the elements and the crystal structures of the ordered room temperature form were characterized via single crystal x‐ray studies. In the Zintl phases the As atoms form chiral ufosan‐anions As with As‐As distances ranging from 238 to 248 pm. Like K₃As₁₁ Rb₃As₁₁ crystallizes with the Na₃P₁₁ structure type (orthorhombic, space group Pbcn, a = 1108.2(2), b = 1533.5(3), c = 1060.1(2) pm, Z = 4), whereas the Cs compound (monoclinic, space group C2/c, a = 1324.5(7), b = 1524.5(9), c = 1937.2(11) pm, β = 95.29(1)°, Z = 8) forms a new structure type. The crystallographic relationship between the two structure types and the anion packings in the plastic crystalline high temperature forms are discussed.     

Bismuth Polyanions in Solution: Synthesis and Structural Characterization of (2, 2, 2‐crypt‐A)2Bi4 (A = K,Rb) and the Formation of the Laves Phases ABi2 (A = K,Rb, Cs) from Solution

The possibility to synthesize and isolate different types of bismuth polyanions by dissolving various intermetallic precursors (binary samples from A‐Bi or ternary samples from A‐A'‐Bi systems, A and A' = K, Rb, Cs) in ethylenediamine or dimethylform amide in the presence of sequestering agents (2, 2, 2‐crypt or 18‐crown‐6) was investigated. The crystals of (2, 2, 2‐crypt‐K)₂Bi₄ ( 1 ) and (2, 2, 2‐crypt‐Rb)₂Bi₄ ( 2 ) compound were obtained from such solutions, the latter for the first time, and their structures were determined. The two compounds are isostructural (P1, Z=1, a = 11.052(2) Å, b = 11.370(2) Å, c = 11.698(2) Å, α = 61.85(3) °, β = 82.58(3) °, γ = 81.87(3) °, R₁ = 0.058, wR² = 0.149 for 1 and a = 11.181(2) Å, b = 11.603(2) Å, c = 11.740(2) Å, α = 61.96(3) °, β = 81.45(3) °, γ = 82.26(3) °, R₁ = 0.041, wR² = 0.109) and contain Bi₄^2— square planar cluster anions and cryptated alkali metal cations. In the case of the presence of 18‐crown‐6 the Laves phases ABi₂ (A = K, Rb, Cs) could be isolated from the solutions. A mechanism for the formation of ABi₂ is proposed.     

Alkalimetall‐Oxoantimonate: Synthesen,Kristallstrukturen und Schwingungsspektren von ASbO2 (A = K,Rb), A4Sb2O5 (A = K,Rb, Cs) und Cs3SbO4

Alkaline Metal Oxoantimonates: Synthesis, Crystal Structures, and Vibrational Spectroscopy of ASbO₂ (A = K, Rb), A₄Sb₂O₅ (A = K, Rb, Cs), and Cs₃SbO₄ The compounds ASbO₂ (A = K/Rb; monoclinic, C2/c, a = 785.4(3)/799.6(1) pm, b = 822.1(4)/886.32(7) pm, c = 558.7(3)/559.32(5) pm, β = 124.9(1)/123.37(6)°, Z = 4) are isotypic with CsSbO₂ and the corresponding bismutates. The structures of the antimonates A₄Sb₂O₅ (A = K/Rb: orthorhombic, Cmcm, a = 394.9(1)/407.34(7) pm, b = 1807.4(1)/1893.5(1) pm, c = 636.34(9)/655.60(8) pm, Z = 2) and Cs₄Sb₂O₅ (monoclinic, Cm, a = 1059.81(7) pm, b = 692.68(8) pm, c = 811.5(1) pm, β = 98.7(1)°, Z = 2) both contain the anion [O₂SbOSbO₂]^4–. Cs₃SbO₄ (orthorhombic, Pnma, a = 1296.1(1) pm, b = 919.24(8) pm, c = 679.95(6) pm, Z = 4) crystallizes with the K₃NO₄ structure type.     

Das Zintl-Konzept als Syntheseprinzip: Darstellung und Kristallstrukturen von K2Ba3Sb4 und KBa4Sb3O

Starting from the Zintl-Concept: Syntheses and Crystal Structures of K₂Ba₃Sb₄ and KBa₄Sb₃O The black, metallic lustrous, air sensitive compounds K₂Ba₃Sb₄ and KBa₄Sb₃O were prepared from melts of mixtures of the elements, in case of KBa₄Sb₃O with a stoichiometric amount of Sb₂O₃. K₂Ba₃Sb₄ crystallizes in the orthorhombic system, space group Pnma (a = 870.5(1) pm, b = 1770.2(2) pm, c = 923.6(1) pm, Z = 4) and is the first Sb compound with only [Sb₂]^4– dumbbells in the anionic partial structure. The compound KBa₄Sb₃O crystallizes in the tetragonal system, space group I4/mcm (a = 882.4(1) pm, c = 1659.4(2) pm, Z = 4). In this structure antimony forms [Sb₂]^4–-dumbbells and isolated ions Sb^3–. Each antimony ion of the dumbbells – in K₂Ba₃Sb₄ as well as in KBa₄Sb₃O – is coordinated in form of a bicapped skew trigonal prism. The isolated Sb^3– ions in KBa₄Sb₃O center bicapped tetragonal antiprisms, the O^2– ions occupy tetrahedral voids.     

Zintl‐Verbindungen mit Gold und Germanium: M3AuGe4 mit M = K,Rb und Cs

Zintl‐Compounds with Gold and Germanium: M₃AuGe₄ with M = K, Rb, Cs Black, brittle single crystals of M₃AuGe₄ with M = K, Rb, Cs were synthesized by reactions of alkali metal azides (MN₃) with gold sponge and germanium powder at T = 1120 K. The structures of the compounds (space group Pmmn, Z = 2, K₃AuGe₄: a = 6.655(1)Å, b = 11.911(2)Å, c = 6.081(1)Å; Rb₃AuGe₄: a = 6.894(1)Å, b = 12.421(1)Å, c = 6.107(1)Å; Cs₃AuGe₄: a = 7.179(1)Å, b = 12.993(2)Å, c = 6.112(2)Å) were determined from X‐ray single‐crystal diffractometry data. The semiconducting compounds contain equation/tex2gif-stack-2.gif[AuGe₄]‐chains with P₄‐analogous Ge₄‐tetrahedra which are connected by μ₂‐bridging gold atoms in a distorted tetrahedral Ge‐coordination.     

Cs5Sb8 und β‐CsSb: Zwei neue binäre Zintl‐Phasen

Cs₅Sb₈ and β‐CsSb: Two New Binary Zintl Phases The anion in the crystal structure of the new Zintl phase Cs₅Sb₈ synthesized from the elements (monoclinic, space group P2₁/c, a = 724.4(2) pm, b = 1135.2(3) pm, c = 2750.9(8) pm, β = 96.663(5)°, Z = 4) consists of two and three bonded Sb atoms, which are connected to form puckered nets with 5 and 28 membered rings. β‐CsSb (monoclinic, space group P2₁/c, a = 1519.4(3) pm, b = 734.0(2) pm, c = 1432.2(2) pm, β = 113.661(3)°, Z = 4) crystallizes with a superstructure of the LiAs structure type. As in the α phase (NaP type), twobonded Sb^‐ atoms form neary ideal 4₁ screx chains. In contrast to the α phase the helices have opposite chirality.     

Vibrational Spectra of Cluster Anions. 2. Vibrational Spectra of Compounds with the Cluster Anions [E4]4−: M4E4 (M = K,Rb, Cs; E = Ge,Sn) and β‐Na4Sn4

Vibrational spectra of the compounds M₄E₄ (M = K, Rb, Cs; E = Ge, Sn) and of β‐Na₄Sn₄ with the cluster anions [E₄]^4? were analysed based on the point group of isolated tetrahedranide units. The lower individual symmetry of the anions in the real structure being more patterned and complex primarily affects the spectra of the tetrahedro‐tetragermanides. ν₃(F₂) clearly splits both in Raman and IR and in the case of K₄Sn₄ only in IR. Rb₄Sn₄ and Cs₄Sn₄ exhibit very simple spectra with three bands in Raman and one band in IR. The breathing mode ν₁(A₁) for the quasi isolated [E₄]^4? cluster appears only in the Raman spectrum and is hardly influenced by the structural environment and by the nature of the alkali metal cations: ν₁(A₁) = 274 cm^?1 ([Ge₄]^4?) and 183‐187 cm^?1 ([Sn₄]^4?), respectively. The calculated valence force constants f_d(E–E) are: [Ge₄]^4? : f_d = 0.89 Ncm^?1 ( K ), 0.87 Ncm^?1 ( Rb ), 0.86 Ncm^?1 ( Cs ) and [Sn₄]^4? : 0.67 Ncm^?1 ( Na ), 0.66 Ncm^?1 ( K ), 0.67 Ncm^?1 ( Rb ), 0.68 Ncm^?1 ( Cs ). Both, the frequencies and the force constants fit well into the range previously reported.     

Pniktogenidostannate(IV) mit isolierten Tetraeder‐Anionen: Neue Vertreter (E1)4(E2)2[Sn(E15)4] (mit E1 = Na,K; E2 = Ca,Sr, Ba; E15 = P,As, Sb,Bi) vom Na6[ZnO4]‐Typ und die Überstrukturvariante von K4Sr2[SnAs4]

Pnictogenidostannates(IV) with Discrete Tetrahedral Anions: New Representatives (E1)₄(E2)₂[Sn(E15)₄] (with E1 = Na, K; E2 = Ca, Sr, Ba; E15 = P, As, Sb, Bi) of the Na₆[ZnO₄] Type and the Superstructure Variant of K₄Sr₂[SnAs₄] The silvery to dark metallic lustrous compounds (E1)₄(E2)₂[Sn(E15)₄] (E1 = Na, K; E2 = Ca, Sr, Ba; E15 = P, As, Sb, Bi) were prepared from melts of stoichiometric mixtures of the elements. They crystallize in the Na₆[ZnO₄]‐type structure (hexagonal, space group: P6₃mc, Z = 2; Na₄Ca₂[SnP₄]: a = 938.94(7), c = 710.09(8) pm; K₄Sr₂[SnAs₄]: a = 1045.0(2), c = 767.0(1) pm; K₄Ba₂[SnP₄]: a = 1029.1(6), c = 780.2(4) pm; K₄Ba₂[SnAs₄]: a = 1051.3(1), c = 795.79(7) pm; K₄Ba₂[SnSb₄]: a = 1116.9(2), c = 829.2(1) pm; K₄Ba₂[SnBi₄]: a = 1139.5(2), c = 832.0(2) pm). The anionic partial structure consists of tetrahedra [Sn(E15)₄]^8– orientated all in the same direction along [001]. In the cationic partial structure one of the two cation positions is occupied statistically by alkali and alkaline earth metal atoms. Up to now only for K₄Sr₂[SnAs₄] a second modification could be isolated, forming a superstructure type with three times the unit cell volume (hexagonal, space group: P6₃cm, Z = 6; a = 1801.3(2), c = 767.00(9) pm) and an ordered cationic partial structure.     

The Silicides M4Si4 with M = Na,K, Rb,Cs, and Ba2Si4 – NMR Spectroscopy and Quantum Mechanical Calculations

The Zintl phases M₄Si₄ with M = Na, K, Rb, Cs, and Ba₂Si₄ feature a common structural unit, the Si₄^4– anion. The coordination of the anions by the cations varies significantly. This allows a systematic investigation of the bonding situation of the anions by ²⁹Si NMR spectroscopy. The compounds were characterized by powder X‐ray diffraction, differential thermal analysis, magnetic susceptibility measurements, ²³Na, ²⁹Si, ⁸⁷Rb, ¹³³Cs NMR spectroscopy, and quantum mechanical calculation of the NMR coupling parameter. The chemical bonding was investigated by quantum mechanical calculations of the electron localizability indicator (ELI). Synthesis of the compounds results for all of them in single phase material. A systematic increase of the isotropic ²⁹Si NMR signal shift with increasing atomic number of the cations is observed by NMR experiments and quantum mechanical calculation of the NMR coupling parameter. The agreement of experimental and theoretical results is very good allowing an unambiguous assignment of the NMR signals to the atomic sites. Quantum mechanical modelling of the NMR shift parameter indicates a dominant influence of the cations on the isotropic ²⁹Si NMR signal shift. In contrast to this a negligible influence of the geometry of the anions on the NMR signal shift is obtained by these model calculations. The origin of the systematic variation of the isotropic NMR signal shift is not yet clear although an influence of the charge transfer estimated by calculation using the QTAIM approach is indicated.     

Alkalimetalltetraethinylozincate und ‐cadmate AI2M(C2H)4 (AI = Na — Cs,M = Zn,Cd): Synthese,Kristallstruktur und spektroskopische Eigenschaften

Alkali Metal Tetraethinylozincates and ‐cadmates A^I₂M(C₂H)₄ (A^I = Na — Cs, M = Zn, Cd): Synthesis, Crystal Structures, and Spectroscopic Properties By reaction of A^IC₂H (A^I = Na — Cs) with divalent zinc and cadmium salts in liquid ammonia the alkali metal tetraethinylozincates and ‐cadmates A^I₂M(C₂H)₄ (M = Zn, Cd) were accessible as polycrystalline powders. While Na₂M(C₂H)₄ is amorphous to X‐rays and the crystal structure of Cs₂Zn(C₂H)₄ could not be solved up to now, the remaining compounds are isotypic to the already known crystal structures of the potassium compounds, as was deduced from powder diffraction with X‐rays and synchrotron radiation. They crystallise in the tetragonal space group I4₁a, contain [M(C₂H)₄]^2— tetrahedra and show structural relationships to the scheelit and anatas structure types. Raman spectroscopic investigations confirm the existence of tetrahedral fragments with C‐C triple bonds in the alkali as well as in the amorphous alkaline earth metal compounds A^IIM(C₂H)₄ (A^II = Mg — Ba, M = Zn, Cd).     

A New Family of Binary Layered Compounds of Platinum with Alkali Metals (A = K,Rb, Cs)

By reacting platinum with alkali metals (A = K, Rb, Cs) a new family of binary alkali metal platinides has been synthesized and characterized by chemical analysis, X‐ray powder diffraction, thermal analysis (DTA and DSC), and magnetic measurements. All three compounds exhibit similar XRD‐patterns with strong reflections that can be indexed on the basis of a rhombohedral crystal system (K_xPt: a = 2.6462(1), c = 17.123(1); Rb_xPt: a = 2.6415(1) Å, c = 17.871(1) Å; Cs_xPt: a = 2.6505(1) Å, c = 18.536(1) Å; x < ½. The a lattice constant is independent on the alkali metal used and of value close to the Pt–Pt distance in NaPt₂ (2.645Å). The c parameter increases monotonically with the growing atomic radius of the alkali metal. The average structure of the alloys consists of cubic close packed layers of platinum atoms with layers of disordered alkali metals in between. For all compounds besides the strong reflections small satellites are observed which cannot be indexed together with the rhombohedral peaks in any rational 3‐dimensional lattice. However, these satellites can be indexed as incommensurate modulations within the ab plane (found propagation vectors k = (0.1011, 0.2506, 0) for Cs_xPt, and k = (0.0168, 0.2785, 0) for Rb_xPt).     

Zur Kenntnis von Alkalimetaselenoarseniten Darstellung und Kristallstrukturen von MAsSe2, M = K,Rb, Cs

Concerning Alkali Metal Metaselenoarsenites. Preparation and Crystal structures of MAsSe₂, M = K, Rb, Cs The metaselenoarsenites MAsSe₂, M = K, Rb, Cs were prepared by methanolothermal reaction of M₂CO₃ with As₂Se₃ at a temperature of 130°C. Their X-ray structural analyses demonstrated that the compounds contain polymetaselenoarsenite anions [AsSe₂^?]_∞, in which the basic units are ψ-AsSe₃ tetrahedra, which are linked via shared corners into infinite chains. Vierer single chains are observed for KAsSe₂ and RbAsSe₂, zweier single chains for CsAsSe₂. The stretching units s are respectively 3,157, 2.336 and 3,378 Å. The relationship between the conformation of metaselenoarsenite chains and cation size is discussed.     

Synthesis and structural characterization of the type‐I clathrates K8AlxSn46–x and Rb8AlxSn46–x (x ≃ 6.4–9.7)

Exploratory studies in the systems A–Al–Sn (A = K and Rb) yielded the clathrates K₈Al_xSn_46–x (potassium aluminium stannide) and Rb₈Al_xSn_46–x (rubidium aluminium stannide), both with the cubic type‐I structure (space group Pmn, No. 223; a ? 12.0 Å). The Al:Sn ratio is close to the idealized A₈Al₈Sn₃₈ composition and it is shown that it can be varied slightly, in the range of ca ±1.5, depending on the experimental conditions. Both the (Sn,Al)₂₀ and the (Sn,Al)₂₄ cages in the structure are fully occupied by the guest alkali metal atoms, i.e. K or Rb. The A₈Al₈Sn₃₈ formula has a valence electron count that obeys the valence rules and represents an intrinsic semiconductor, while the experimentally determined compositions A₈Al_8±xSn_38?x suggest the synthesized materials to be nearly charge‐balanced Zintl phases, i.e. they are likely to behave as heavily doped p‐ or n‐type semiconductors.     

Die Heptabromodigermanate(II) A3Ge2Br7 (A = Rb,NH4) Synthesen,Charakterisierung und Kristallstrukturen

Heptabromodigermanates(II) A₃Ge₂Br₇ (A ? Rb, NH₄) — Syntheses, Characterization, and Crystal Structures Heptabromodigermanates(II) A₃Ge₂Br₇ (A ? Rb, NH₄) have been obtained by crystallization from aqueous ABr? GeBr₂? HBr solutions. The compounds can be characterized as double salts ABr · 2 AGeBr₃, because the crystal structures (monoclinic, space group P2₁/c, Z = 4) consist of pyramidal GeBr₃ groups.     

Synthesis,Crystal and Electronic Structure of Layered AMSb Compounds (A = Rb,Cs; M = Zn,Cd)

Synthesis, crystal structure, thermal stability, and electronic band structure of four new metal antimonides AMSb (A = Rb, Cs; M = Zn, Cd) are reported. CsZnSb and RbZnSb crystallize in the hexagonal ZrBeSi structure type, in a P6₃/mmc space group (no. 194, Z = 2) and unit cell dimensions of a = 4.5588(2)/4.5466(4) Å and c = 11.9246(6)/11.0999(10) Å. CsCdSb and RbCdSb crystallize in the tetragonal PbFCl structure type in a P4/nmm space group (no. 129; Z = 2) and unit cell parameters of a = 4.8884(5)/4.8227(3) Å and c = 8.8897(9)/8.5492(7) Å. All four compounds are air- and water-sensitive and are shown through DSC measurements to decompose between 975 K and 1060 K. Analysis of the calculated electronic band structure shows that the Zn-containing antimonides are topologically trivial narrow bandgap semiconductors, whereas Cd-containing compounds exhibit a band inversion along Γ-Z direction.     

Phasenbeziehungen im System LiGa?Sn und die Kristallstrukturen der intermediären Phasen LiGaSn und Li2Ga2Sn

Phase Relations in the System LiGa? Sn and the Crystal Structures of the Intermediate Compounds LiGaSn and Li₂Ga₂Sn The quasibinary system LiGa? Sn contains the intermediate ternary phases Li₇Ga₇Sn₃, Li₂Ga₂Sn, Li₅Ga₅Sn₃, Li₃Ga₃Sn₂ and LiGaSn. Single crystals of LiGaSn (a = 632.9(4) pm, Fd3m, Z = 4), Li₃Ga₃Sn₂ (a = 445.4(3), c = 1 090.0(2) pm, hP*), Li₅Ga₅Sn₃ (a = 447.0(4), c = 4 220.0(9) pm, hP*) and Li₂Ga₂Sn (a = 441.1(2), c = 2 164.5(7) pm, P6₃/mmc, Z = 4) have been grown from the melt. The crystal structures of LiGaSn and Li₂Ga₂Sn have been determined by single crystal X-ray methods (R = 0.029 bzw. 0.107 respectively). The crystal structure of LiGaSn contains a sphalerite-type Ga/Sn-arrangement, the Ga/Sn-arrangement of Li₂Ga₂Sn corresponds to a stacking variant of the wurtzite- and sphalerite-type. The compounds can be classified in terms of the Zintl concept.     

[Rb4Sn9] — A Low Dimensional Arrangement of Zintl Ions in [Rb(18‐crown‐6)]2Rb2[Sn9](en)1.5

The compound [Rb(18‐crown‐6)]₂Rb₂[Sn₉](en)_1.5 ( 1 ) was synthesized from an alloy of formal composition K₂Rb₂Sn₉ by dissolving in ethylenediamine (en) followed by the addition of 18‐crown‐6 and toluene. 1 crystallizes in the monoclinic space group P2₁/n with a = 10.557(2), b = 25.837(5), c = 20.855(4)Å, β = 102.39°, and Z = 4. The structure consists of [Sn₉]^4— cluster anions, which are connected via Rb atoms to infinite [Rb₄Sn₉] layers. The layers of binary composition are separated by the crown ether molecules. The crown ether molecules are bound by one side via the Rb atoms to the [Sn₉]^4— anions. The other side, which is turned away from the Rb atoms, shows only weak van der Waals interactions to the crown ether molecules of the next layer. Comparison with other compounds of similar composition shows, that the variation of the alkali metals and the complexing organic molecules leads to the low dimensional arrangement of the clusters.     

Die Kristallstrukturen von KNdTe4, RbPrTe4 und RbNdTe4 — Untersuchungen zur thermischen Stabilität von KNdTe4 sowie Bemerkungen zu einigen anderen Vertretern der Zusammensetzung ALnTe4 (A = K,Rb, Cs und Ln = Seltenerd‐Metall)

Crystal Structures of KNdTe₄, RbPrTe₄, and RbNdTe₄ — Investigations concerning the Thermal Stability of KNdTe₄ as well as some Remarks concerning Additional Representatives of the Composition ALnTe₄ (A = K, Rb, Cs and Ln = Rare Earth Metal) Of the compounds ALnQ₄ (A = Na, K, Rb, Cs; Ln = Lanthanoid; Q = S, Se and Te) the crystal structures of the three new tellurides KNdTe₄, RbPrTe₄ and RbNdTe₄ were determined by X‐ray single‐crystal structure analysis and of the three additional new ones KCeTe₄, KPrTe₄ and CsNdTe₄ by X‐ray powder diffraction experiments. All six new compounds are isotypic with KCeSe₄. Characteristic for the crystal structure of the compounds mentioned above are layers built from (Q₂)^2— dumbbells in form of 4.3².4.3 nets with embedded cations A⁺ and Ln³⁺ between them, which are coordinated eightfold in form of square‐shaped antiprisms by Q ions. The distances Te‐Te within the dumbbells were found to be 277.8(2) pm for all investigated tellurides. By combination of X‐ray diffraction and DTA measurements it was shown that the compound KNdTe₄ is metastable at ambient temperature with a limited existence range between the temperatures 260 and 498 °C.     

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.