Die kubischen Phasen Na16(ARb6)Sb7, Verbindungen mit den Anionen A = Rb−, Na−, Au−, I−

The Cubic Phases Na₁₆(ARb₆)Sb₇, Compounds with the Anions A = Rb^?, Na^?, Au^?, I^? The novel compounds Na₁₆(ARb₆)Sb₇ have been synthesized from the elements in sealed Nb ampoules at 873 K (A = Rb) and 823 K (A = I, Na, Au). They form brittle cuboctahedra (silver metallic; A = Rb) and irregular polyhedra (silver metallic lustre; A = Na, I; golden metallic lustre; A = Au). They rapidly decompose in moist air to gray products. Their crystal structures have been determined by single crystal X-ray crystallography (A = Rb: a = 1565.8(2) pm; A = I: a = 1563.3(2) pm; A = Na: a = 1562.6(2) pm; A = Au: a = 1560.7(2) pm). They crystallize cubically in the space group Fm3 m (no. 225) with Z = 4 formula units and are isotypic with Sc₁₁Ir₄. The compounds are ZINTL phases and their structures can be described as an eightfold defect variant of the Li₃Bi type of structure (cF128-8; a = 2a′(Li₃Bi)). The Sb atoms form a network of cuboctahedra, centered alternatingly by a SbNa₈ cube or a ARb₆ octahedron. Main structural features are the anions A^? within the Rb₆ octahedron. Supporting the existence of A^? are the isotypical compounds with the more common anion forming elements (A = Au, I), as well as electrostatic potential considerations together with calculations of the volume increments. The semiconducting properties (E_g = 0.33 eV) of Na₁₆(RbRb₆)Sb₇, as well as the diamagnetism χ_mol = ?508 × 10^?6 cm³ mol^?1, are in accordance with those to be expected from the Zintl concept.     

Carbonat-isostere Anionen [SnX3]5− in den Verbindungen Rb6[SnX3]O0,5 und Cs6[SnX3]O0,5 mit X = As,Sb und Bi

Carbonate Isostructural Anions [SnX₃]^5? in the Compounds Rb₆[SnX₃]O_0.5 and Cs₆[SnX₃]O_0.5 with X = As, Sb, and Bi The metallic shining compounds Rb₆[SnX₃]O_0.5 and Cs₆[SnX₃]O_0.5 with X = As, Sb, and Bi were prepared from the melt starting from adequate mixtures of the elements and SnO₂. They crystallize in the hexagonal system (space group P6₃/mmc, No. 194, Z = 2) with the lattice constants mentioned in ?Inhaltsübersicht”?. In the structures of the isotypic compounds tin and the main group(V) elements build up trigonal planar anions [SnX₃]^5? with X = As, Sb, and Bi isostructural to the carbonate anion, oxygen forms isolated O^2? ions. The bond lengths Sn? X are significantly shortened with respect to the sums of Pauling covalent radii. The atoms of the units [SnX₃]^5? are coordinated by alkali metal cations forming trigonal prisms and the O^2? anions occupy octahedral holes.     

Interaction of RT3 (R=Ce, Y; T=Ni, Co) intermetallic compounds with alkaline solutions of MBH4 (M=Na, K, Rb, and Cs)

The interaction of RT₃ (R=Ce, Y; T=Ni, Co) intermetallic compounds (IMC)with alkaline solutions of MBH₄ (M=Na, K, Rb, and Cs) was studied in the temperature range of 298–318 K. For all intermetallic compounds, the reaction of catalytic hydrolysis of NaBH₄ is zero order with respect to MBH₄ and first order with respect to RT₃. The reaction rate decreases and the activation energy of the catalytic hydrolysis of MBH₄ increases in the following order. NaBH₄, KBH₄, RbBH₄, and CsBH₄. The hydride phases RT₃H_x (x2.3—3.9) were synthesized by the interaction of RT₃ IMC with alkaline solutions of MBH₄. They are similar in composition to the products formed in the reaction of RT₃ with gaseous hydrogen at high pressure. The rate of hydrogenation of RT₃ in alkaline solutions of MBH₄ decreases on going from sodium to cesium. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 921–923, May, 1997.     

Ge Pairs and Sb Ribbons in Rare‐Earth Germanium Antimonides RE12Ge7−xSb21 (RE=La–Pr)

The ternary rare‐earth germanium antimonides RE₁₂Ge_7?xSb₂₁ (RE=La–Pr; x=0.4–0.5) are synthesized by direct reactions of the elements. Single‐crystal X‐ray diffraction studies indicate that they adopt a new structure type (space group Immm, Z=2, a=4.3165(4)–4.2578(2) Å, b=15.2050(12)–14.9777(7) Å, c=34.443(3)–33.9376(16) Å in the progression from RE=La to Pr), integrating complex features found in RE₆Ge_5?xSb_11+x and RE₁₂Ga₄Sb₂₃. A three‐dimensional polyanionic framework, consisting of Ge pairs and Sb ribbons, outlines large channels occupied by columns of face‐sharing RE₆ trigonal prisms. These trigonal prisms are centered by additional Ge and Sb atoms to form GeSb₃ trigonal‐planar units. A bonding analysis attempted through a Zintl–Klemm approach suggests that full electron transfer from the RE atoms to the anionic substructure cannot be assumed. This is confirmed by band‐structure calculations, which also reveal the importance of Ge? Sb and Sb? Sb bonding. Magnetic measurements on Ce₁₂Ge_6.5Sb₂₁ indicate antiferromagnetic coupling but no long‐range ordering down to 2 K.     

Expanding the 0D Rb7M3X16 (M=Sb,Bi; X=Br,I) Family: Dual-Band Luminescence in Rb7Sb3Br16

Inorganic, lead-free metal halides are widely sought after following the rise of the halide perovskites as outstanding optoelectronic materials, due to their enhanced stability and reduced toxicity. Herein, we report on the solvothermal synthesis of Rb₇Sb₃Br₁₆, which exhibits a 0D structure comprised of [SbBr₆]³⁻ octahedra and edge-sharing bioctahedra [Sb₂Br₁₀]⁴⁻ dimers that order into layers along the c-axis. This all-inorganic material is air-stable and exhibits weak orange photoluminescence (PL) at room temperature. Low-temperature PL and PL excitation (PLE) measurements reveal the presence of two distinct emission bands that originate from these structural units, with the high-energy emission quenching as temperature rises beyond 150 K. We are also able to obtain Rb₇Bi₃Br₁₆ and Rb₇Bi₃I₁₆ which both crystallize in orthorhombic symmetry, with Rb₇Bi₃Br₁₆ presenting weak low-temperature luminescence while Rb₇Bi₃I₁₆ is non-luminescent. This work expands the library of emissive inorganic metal halides and provides further evidence for the efficacy of low-dimensional Sb−X luminescent centers based on octahedral and edge-sharing [Sb₂X₁₀]⁴⁻ dimers.     

Alkalimetallbismutide ABi und ABi2 (A = K,Rb, Cs) — Synthesen,Kristallstrukturen, Eigenschaften

Alkali Metal Bismuthides ABi and ABi₂ — Synthesis, Crystal Structure, Properties The Zintl phases ABi (A = K/Rb/Cs; monoclinic, space group, P2₁/c, a = 1422.3(2)/1474.2(2)/1523.7(3), b = 724.8(1)/750.2(1)/773.7(1), c = 1342.0(2)/1392.1(2)/1439.9(2) pm and β = 113.030(3)/113.033(2)/112.722(3)°, Z = 16) crystallize with the β‐CsSb structure type containing chains of two‐connected Bi atoms. Hence, and according to calculated electronic structures, they are semiconductors with small band gaps of approx. 0.5 eV. In contrast, the compounds ABi₂ (A = K/Rb/Cs; cubic, space group Fd3¯m, a = 952.1(2)/962.4(8)/972.0(3) pm, Z = 8) belong to the Laves phases, showing a typical metallic electrical conductivity and no band gaps.     

[{(CO)5Cr}6Ge6]2−, A Molecular Organometallic Derivative of the Unknown Zintl Ion [Ge6]2−

Octahedral clusters from p-block elements are rare ; however, the only known molecular aggregate of this kind, [{(CO)₅Cr}₆Sn₆]²⁻, has now been supplemented by the isoelectronic cluster [{(CO)₅Cr}₆Ge₆]²⁻ ( 1 ).     

Tetrahedral [Tt4]4– Zintl Anions Through Solution Chemistry: Syntheses and Crystal Structures of the Ammoniates Rb4Sn4·2NH3, Cs4Sn4·2NH3, and Rb4Pb4·2NH3

The crystalline isotypic solvates Rb₄Sn₄·2NH₃, Cs₄Sn₄·2NH₃, and Rb₄Pb₄·2NH₃ have been synthesized using the direct reduction of elemental tin or tetraphenyltin, respectively, with heavier alkali metals or the dissolution of the binary phase RbPb in liquid ammonia. These compounds contain the cluster ions [Sn₄]^4– or [Pb₄]^4– respectively. This is the first time that[Tt₄]^4– ions (Tt = tetrels) are detected as result of a solution reaction. The accommodation of the ammonia molecules, which build up ion‐dipole interactions to alkali metal cations, requires some modifications of the crystal structures compared to the binary phases RbSn, CsSn, and RbPb. The tetrahedral [Tt₄]^4– anions have a slightly lower coordination by Rb⁺ or Cs⁺ cations and, furthermore, the intercluster distances show a remarkable increase.     

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.     

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.     

[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.     

Peculiar All‐Metal σ‐Aromaticity of the [Au2Sb16]4− Anion in the Solid State

Gas‐phase clusters are deemed to be σ‐aromatic when they satisfy the 4n+2 rule of aromaticity for delocalized σ electrons and fulfill other requirements known for aromatic systems. While the range of n values was shown to be quite broad when applied to short‐lived clusters found in molecular‐beam experiments, stability of all‐metal cluster‐like fragments isolated in condensed phase was previously shown to be mainly ascribed to two electrons (n=0). In this work, the applicability of this concept is extended towards solid‐state compounds by demonstrating a unique example of a storable compound, which was isolated as a stable [K([2.2.2]crypt)]⁺ salt, featuring a [Au₂Sb₁₆]^4? cluster core possessing two all‐metal aromatic AuSb₄ fragments with six delocalized σ electrons each (n=1). This discovery pushes the boundaries of the original idea of Kekulé and firmly establishes the usefulness of the σ‐aromaticity concept as a general idea for both small clusters and solid‐state compounds.