X‐Ray Crystal Structures of Hexa‐oxotellurate Complexes of Ruthenium(VI) and Silver(III): Na6[RuO2{TeO4(OH)2}2]·16H2O and Na5[Ag{TeO4(OH)2}2]·16H2O

X‐ray crystal structures are reported for Na₆[RuO₂{TeO₄(OH)₂}₂]·16H₂O and Na₅[Ag{TeO₄(OH)₂}₂]·16H₂O which contain respectively Ru^VI and Ag^III coordinated to chelating bidentate tellurate ([TeO₄(OH)₂]⁴⁻) groups. Na₆[RuO₂{TeO₄(OH)₂}₂]·16H₂O: Space group P1¯, Z = 2, lattice dimensions at 120 K; a = 6.9865(1), b = 8.7196(2), c = 11.7395(2)Å, α = 74.008(1), β = 79.954(1), γ = 88.514(1)°; R1 = 0.025. Na₅[Ag{TeO₄(OH)₂}₂]·16H₂O: Space group P1¯, Z = 2, lattice dimensions at 120 K; a = 5.888(1), b = 8.932(1), c = 12.561(2)Å, α = 98.219(6), β = 97.964(9), γ = 93.238(14)°; R1 = 0.047.     

Ein Oxotellurat (VI) neuen Typs: Rb6[TeO5] [TeO4]

A New Type of Oxotellurates (VI): Rb₆[TeO₅] [TeO₄] For the first time single crystals of Rb₆Te₂O₉ was obtained by annealing intimate mixtures of the binary oxides (closed Ag-cylinder in supremax-glass ampoule, 680°C, 45 d). The structure elucidation (four-circle diffractometer, AgKα, 2083 I₀(hkl); R = 9.5%, R_w = 6.6%) confirms the space group C2/c with a = 1207.5(7), b = 1266.3(5), c = 1105.3(6) pm, β = 123.1(1)⁰, Z = 4 (Guinier-Simon photographs). Characteristic for this structure are ?isolated”? trigonal bipyramidal groups of [TeO₅] and ?isolated”? tetrahedral groups of [TeO₄], so we prefere to name the new compound Rb₆[TeO₅][TeO₄]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, the latter derived from Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Oxydation intermetallischer Phasen: CsK2[AuO2] aus CsAu + K2O2

Oxidation of Intermetallic Phases CsK₂[AuO₂] from CsAu+K₂O₂ We prepared the hitherto unknown CsK₂[AuO₂] [Heating mixtures of CsAu and K₂O_2,2; 1:1; gives single crystals (Ag-cylinder, 430°C, 6d)]. The single crystals are light blue, nearly colourless, and transparent. A new type of structure is found. The single crystal data are: Pnma; a = 1256.5(5), b = 727.3(2), c = 627.9(2)pm, Z = 4; four-circle diffractometer PW 1100, MoKα;849 out of 871 I₀(hkl), R = 7.3% and R_w = 6.3%. The Madelung Part of Lattice Energy, MAPLE, is calculated.     

Das erste quaternäre Oxocobaltat(I): CsK2[CoO2]

The First Quaternary Oxide of Monovalent Cobalt: CsK₂[CoO₂] Dark-red single crystals of CsK₂[CoO₂] were obtained via ?reaction with the cyliner surface”? by heating powders of Cs₂K₂Cd₃O₅ in closed Co-cylinders at 500°C during 48 d. Structure solution and refinement (four-circle diffractometer data, MoKα , 147 independent I_o(hkl), none was omitted, R = 3.42%, R_w = 2.24%) show close relationship with RbNa₂[NiO₂] [2]. The lattice-constants are: (powder data, standard deviations in parentheses) MAPLE calculations, investigations of magnetism and EPR measurement add to the monovalence of Co.     

Zur Kenntnis der Na5[GaO4]-Verwandtschaft: KNa4[GaO4] und CsK4[GaO4]

About the Na₅[GaO₄]-Relationship: KNa₄[GaO₄] and CsK₄[GaO₄] KNa₄[GaO₄] was newly prepared from binary oxides (powders) and also from KGaO₂/Na₂O/K₂O (colourless columnar single crystals) in a closed Ag-cylinder at 600 and 650°C. Space group Pbca with a = 1046.1(2), b = 596.3(1), c = 1871.1(3) pm, Z = 8 [Four-circle-diffractometer data, 1138 I₀(hkl), MoKα, R = 8.29, R_w = 6.76%, anisotropic refinement] (Parameter s. text). Colourless cubic single crystals of hitherto unknown CsK₄[GaO₄] are formed by reaction of K₂O, CsGaO₂, and Cs₂O (surplus) in a closed Au-tube at 580°C. Space group Pbca with a = 1154.7, b = 667.7, c = 2096.6 pm, Z = 8 [Four-circle-diffractometer data, 1798 I₀(hkl), MoKα, R = 7.62, R_w = 7.68%, anisotropic refinement] (Parameter s. text). Both crystal structures belong to the Na₅[GaO₄] type. Structural aspects, ECoN, and MAPLE of KNa₄[GaO₄] and CsK₄[GaO₄] in relation with Na₅[GaO₄] are discussed.     

Über Oxide mit dem “Butterfly-Motiv”: Rb6[Fe2O5] und K6[Fe2O5]

New Oxides with the “Butterfly-Motive”: Rb₆[Fe₂O₅] and K₆[Fe₂O₅] Rb₆[Fe₂O₅] and K₆[Fe₂O₅] were obtained for the first time by annealing intimate mixtures of “Rb₆CdO₄” with CdO (molar ratio 1 : 1.1) and KO_0.48 with CdO (molar ratio 5.9 : 1) respectively in closed Fe-cylinders. Determination and refinement of the crystalstructure confirms the space group C2/m (four-circle-diffractometer data). Rb₆[Fe₂O₅]: Ag Kα , 720 out of 1220 Io(hkl), R = 9.68%, R_w = 6.09%; a = 718.9pm, b = 1183.1 pm, c = 695.4pm, β = 95.05°, Z = 2; K₆[Fe₂O₅]: MoKα , 1214 Out of 12141_o(hkl), R = 3.20070, R_w = 2.48%, a = 691.21 pm, b = 1142.78pm, c = 665.50pm, β = 93.82°, Z = 2. The binuclear unit [O₂FeOFeO₂]^6? already known to be planar with oxoferrates(II) now was observed to be angular here and closely related to Na₆[Be₂O₅].     

Über ein neues Oxoferrat mit „Butterfly-Motiv”︁: K2Na4[Fe2O5]

A New Oxoferrate with “Butterfly-Motiv”: K₂Na₄[Fe₂O₅] Dark red-brown single-crystals of K₂Na₄[Fe₂O₅] were obtained for the first time by heating “K₃Na₃CdO₄” at 500°C in closed Fe-cylinders. Determination and refinement of the crystal structure confirms the space group P4₂/mnm (No. 136). Four-circle diffractometer data: MoKα , 373 out of 373 I_o(hkl); R = 5.3%; R_w = 4.6%; a = 645.94(5), c = 1 039.2(1) pm. In contrast to the already known oxoferrates(II) with the “Butterfly-Motiv”, Rb₆[Fe₂O₅] and K₆[Fe₂O₅] [1], we now found an isotypic structure for K₂Na₄[Fe₂O₅] with the oxocobaltates of Rb₂Na₄[Co₂O₅] and K₂Na₄[Co₂O₅] [2].     

Über „Orthoindate”︁ der Alkalimetalle: Zur Kenntnis von K5[InO4]

A New ?Orthoindate”? of an Alkali Metal: K₅[InO₄] Hitherto unknown K₅[InO₄] was prepared by heating intimate mixtures of K₂O, In₂O₃ and elementar In (molar ratio 10.0 : 1.0 : 4.0) in closed Ni-cylinders (30 days, 500°C) in form of pale red, nearly colourless, transparent, single crystals. Same crystals were obtained by heating mixtures of K₂O, CdO and elementar In (molar ratio 3.1 : 1.0 : 1.0) in closed Ag-cylinders (30 days, 450°C), too. In this case we also found yellow-brown crystals of K₁₄[In₄O₁₃] [1]. Structure determination by four circle diffractometer data (MoKα, 15279 out 17454 I_o(hkl), R = 5.60%, R_w = 5.25%). Space group P1 with a = 1827.9 pm; b = 1694.4 pm; c = 1329.4 pm; α = 113.3°; β = 111.4°; γ = 105.2°; Z = 16. Characteristic feature of the structure are isolated [InO₄]^5?-tetraeder. The Madelung Part of Lattice Energy, MAPLE, the Mean Fictive Ionic Radii, MEFIR, Effective Coordination Numbers, ECoN, and Charge Distribution, VADI, are calculated.     

La2Si2O7 im I—Typ: Gemäß La6[Si4O13][SiO4]2 kein echtes Lanthandisilicat

I‐Type La₂Si₂O₇: According to La₆[Si₄O₁₃][SiO₄]₂ not a Real Lanthanum Disilicate In attempts to synthesize lanthanum telluride silicate La₂Te[SiO₄] (from La, TeO₂, SiO₂ and CsCl, molar ratio: 1 : 1: 1 : 20, 950 °C, 7 d) or fluoride‐rich lanthanum fluoride silicates (from LaF₃, La₂O₃, SiO₂ and CsCl, molar ratio: 5 : 2 : 3 : 17, 700 °C, 7 d) in evacuated silica tubes, colourless lath‐shaped single crystals of hitherto unknown I‐type La₂Si₂O₇ (monoclinic, P2₁/c; a = 726.14(5), b = 2353.2(2), c = 1013.11(8) pm, β = 90.159(7)°) were found in the CsCl‐flux melts. Nevertheless, this new modification of lanthanum disilicate does not contain any discrete disilicate groups [Si₂O₇]^6‐ but formally three of them are dismutated into one catena‐tetrasilicate ([Si₄O₁₃]^10‐ unit of four vertex‐linked [SiO₄]^4‐ tetrahedra) and two ortho‐silicate anions (isolated [SiO₄]^4‐ tetrahedra) according to La₆[Si₄O₁₃][SiO₄]₂. This compound can be described as built up of alternating layers of these [SiO₄]^4‐ and the horseshoe‐shaped [Si₄O₁₃]^10‐ anions along [010]. Between and within the layers the high‐coordinated La ³⁺ cations (CN = 9 ‐ 11) are localized. The close structural relationship to the borosilicates M₃[BSiO₆][SiO₄](M = Ce ‐ Eu) is discussed and structural comparisons with other catena‐tetrasilicates are presented.     

Er4F2[Si2O7][SiO4]: Das erste Selten‐Erd‐Fluoridsilicat mit zwei verschiedenen Silicat‐Anionen

Er₄F₂[Si₂O₇][SiO₄]: The First Rare‐Earth Fluoride Silicate with Two Different Silicate Anions By the reaction of Er₂O₃ with ErF₃ and SiO₂ at 700 °C in sealed tantalum capsules using CsCl as flux (molar ratio 5 : 2 : 3 : 20), the compound Er₄F₂[Si₂O₇][SiO₄] (triclinic, P 1; a = 648.51(5), b = 660.34(5), c = 1324.43(9) pm, α = 87.449(8), β = 85.793(8), γ = 60.816(7)°; V_m = 148.69(1) cm³/mol, Z = 2) is obtained as pale pink platelets or lath‐shaped single crystals. It consists of disilicate anions [Si₂O₇]^6– in eclipsed conformation, ortho‐silicate anions [SiO₄]^4– and isolated [Er₄F₂]¹⁰⁺ units comprising two edge‐shared [Er₃F] triangles. Er³⁺ is surrounded by 7 + 1 (Er1) or 7 (Er2–Er4) anionic neighbors, respectively, of which two are F^– in the case of Er1 and Er4 but only one for Er2 and Er3. The other ligands recruit from oxygen atoms of the different oxosilicate groups. The crystal structure can be described as simple rowing up of the three building groups ([SiO₄]^4–, [Er₄F₂]¹⁰⁺, and [Si₂O₇]^6–) along [001]. The necessity of a large excess of fluoride for a successful synthesis of Er₄F₂[Si₂O₇][SiO₄] will be discussed.     

Über „Lithovanadate”︁: Zur Kenntnis von Rb2[LiVO4] und Cs2[LiVO4]

On ?Lithovanadates”?: Rb₂[LiVO₄] and Cs₂[LiVO₄] By heating of well ground mixtures of the binary oxides [A₂O, Li₂O, V₂O₅, A : Li: V = 2.2 : 1.1 : 1.0 (A = Rb, Cs); Ni-tube, 750° 25 d] we obtained Rb₂[LiVO₄] and Cs₂[LiVO₄] colourless, orthorhombic single crystals. We found a new type of ?Lithovanadate”?-structure: space group Cmc2₁; a = 587.9(1), b = 1170.1(1), c = 793.3(1) pm, Z = 4 (A = Rb) bzw. a = 610.5(1), b = 1222.6(3), c = 815.5(2) pm, Z = 4 (A = Cs). The structure was determined by four-circle diffractometer data [MoKα -radiation; 997 from 1157 I₀(hkl), R = 7.75%, R_w = 5.54% (A = Rb); 686 from 686 I₀(hkl), R = 6.97%, R_w = 4.20% (A = Cs)] parameters see text. The Madelung part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, have been calculated.     

Pyridinium‐Chlorometallate von Lanthanoid‐Elementen. Die Kristallstrukturen von [HPy]2[LnCl5(Py)] mit Ln = Eu,Er, Yb und von [H(Py)2][YbCl4(Py)2] · Py

Pyridinium Chlorometallates of Lanthanoid Elements. Crystal Structures of [HPy]₂[LnCl₅(Py)] mit Ln = Eu, Er, Yb und von [H(Py)₂][YbCl₄(Py)₂] · Py The pyridinium chlorometallates [HPy]₂[LnCl₅(Py)] with Ln = Eu, Er and Yb, as well as [H(Py)₂][YbCl₄(Py)₂]·Py have been obtained by the reaction of diacetone alcohol with solutions of the corresponding metal trichlorides in pyridine at 100 °C. According to the crystal structure determinations the anions [LnCl₅(Py)]^2— are linked by bifurcated Cl···H···Cl bridges with the protons of the [HPy]⁺ cations forming chains along [001]. The anions of [H(Py)₂][YbCl₄(Py)₂]·Py form discrete octahedrons with trans‐positions of the pyridine ligands. [HPy]₂[EuCl₅(Py)] ( 1a ): Space group Pnma, Z = 4, lattice dimensions at —80 °C: a = 1874.4(2), b = 1490.2(2), c = 741.5(1) pm, R₁ = 0.0466. [HPy]₂[ErCl₅(Py)] ( 1b ): Space group Pnma, Z = 4, lattice dimensions at —80 °C: a = 1864.3(1), b = 1480.7(2), c = 739.7(1) pm, R₁ = 0.0314. [HPy]₂[YbCl₅(Py)] ( 1c ): Space group Pnma, Z = 4, lattice dimensions at —80 °C: a = 1858.9(2), b = 1479.0(1), c = 736.8(1) pm, R₁ = 0.0306. [H(Py)₂][YbCl₄(Py)₂]·Py ( 2 ·Py): Space group Ia, Z = 4, lattice dimensions at —80 °C: a = 1865.5(1), b = 827.5(1), c = 1873.4(1) pm, ß = 103.97(1)°, R₁ = 0.0258.     

Das erste zweikernige Oxoferrat(II): „Cs2K4[O2FeOFeO2]”︁

The First Binuclear Oxoferrate(II): ?Cs₂K₄[O₂FeOFeO₂]”? For the first time ?Cs₂K₄[Fe₂O₅]”? was obtained by annealing intimate mixtures of Cs₂O, K₂O, and CsFeO₂ (molar ratio Cs : K : CsFeO₂ 1.3 : 2.1 : 1) in a closed Fe-cylinder (74 d; 470°C) in the form of red single crystals. The structure determination (four-circle diffractometer, MoKα , 760 out of 857 I_o(h kl); R = 5.8%, R_w = 4.6%) confirms the space group C2/m; a = 707.4, b = 1138.5, c = 699.7 pm, β = 91.76°, Z = 2. Essential part of the structure is the binuclear, planar [O(1)₂Fe? O(2)? FeO(1)₂]^6? group which is for the first time observed with oxoferrates(II). Despite different space groups the crystal structure is related to that of Rb₂Na₄[Co₂O₅].     

[PtIn6][GaO4]2 – das erste Oxid mit [PtIn6]‐Oktaedern. Darstellung,Charakterisierung und Rietveldverfeinerung – mit einer Bemerkung zur Mischkristallreihe [PtIn6][GaO4]2–x[InO4]x (0 < x ≤ 1)

[PtIn₆][GaO₄]₂ – The First Oxide Containing [PtIn₆] Octahedra. Preparation, Characterisation, and Rietveld Refinement – With a Remark to the Solid Solution Series [PtIn₆][GaO₄]_2‐x[InO₄]_x (0 < x ≤ 1) The novel oxides [PtIn₆][GaO₄]_2–x[InO₄]_x (0 < x ≤ 1) are formed by heating intimate mixtures of Pt, In, In₂O₃, and Ga₂O₃ in the corresponding stoichiometric ratio in corundum crucibles under an atmosphere of argon (1220 K, 70 h). The compounds are black, stable in air at room temperature, reveal a semiconducting behaviour, and decompose only in oxidizing acids. X‐ray powder diffraction patterns can be indexed by assuming a face centered cubic unit cell with lattice parameters ranging from a = 1001.3(1) pm (x = 0) to a = 1009.3(1) pm (x = 1). According to a Rietveld refinement [PtIn₆][GaO₄]₂ crystallizes isotypic to the mineral Pentlandite (Fm3m, Z = 4, R(profile) = 6.11%, R(intensity) = 3.95%). The characteristic building units are isolated [PtIn₆]¹⁰⁺ octahedra which are linked via [GaO₄]^5– tetrahedra to a three dimensional framework. Starting from [PtIn₆][GaO₄]₂ the substitution of Ga³⁺ ions by larger In³⁺ ions leads to the formation of a solid solution series according to the general formula [PtIn₆][GaO₄]_2–x[InO₄]_x and becomes apparent in an increase of the lattice parameter.     

Darstellung und Kristallstruktur von β-[SeCl3][MoOCl4]

Preparation and Crystal Structure of β-[SeCl₃][MoOCl₄] The reaction of Se₄[MoOCl₄] and Te₄[MoOCl₄] with SOCl₂ as solvent at 150 °C and 80 °C yields [SeCl₃][MoOCl₄] and [TeCl₃][MoOCl₄] respectively within 3 to 6 days as yellow-brown, moisture-sensitive crystals. [TeCl₃][MoOCl₄] was obtained in the already known monoclinic form, while β-[SeCl₃][MoOCl₄] crystallizes in a new polymorphic triclinic form (P1¯, Z = 2, a = 752.7(2), b = 812.8(2), c = 956.9(3) pm, α = 92.55(3)°, β = 111.63(2)°, γ = 107.39(3)°). The structure contains centrosymmetric tetranuclear units ([SeCl₃]₂[Mo₂O₂Cl₈]) which are analogous to the entities found in the structure of [SCl₃][MoOCl₄]. The packing of the molecules in β-[SeCl₃][MoOCl₄] and [SCl₃][MoOCl₄] is distinctely different.     

Das erste Oxothallat(III) vom Formeltyp AA4′[MO4]: CsK4[TlO4]

The First Oxothallate(III) with the Formula Type AA₄′[MO₄]: CsK₄[TlO₄] For the first time CsK₄[TlO₄] was obtained by heating intimate mixtures of K₂O, CdO and CsTl (molar ratio 3.1:1.0:1.0) in closed Ag-cylinders (25 days, 450°C) in form of yellow, transparent single crystals. The structure determination by four circle diffractometer data (MoKα, 1922 out of 2 094 I_o(hkl), R = 2.98, R_w = 2.49) confirms the space group Pbca with lattice constants a = 1 192.1 pm; b = 685.7 pm; c = 2 143.5 pm; Z = 8. The structure is isotypic with Na₅[GaO₄]. The Madelung Part of Lattice Energy, MAPLE, the Mean Fictive Ionic Radii, MEFIR, Effective Coordination Numbers, ECoN, and Charge Distribution, CHARDI, are calculated.     

Die ersten Oxocobaltate(II) mit zweikernigem Anion: Rb2Na4[Co2O5] und K2Na4[Co2O5]

The First Oxocobaltate(II) with Dinuclear Anion: Rb₂Na₄[Co₂O₅] and K₂Na₄[Co₂O₅] By heating of well ground mixtures of the binary oxides [A₂O, Na₂O, ?CoO”?, A:Na:Co = 1.00:2.00:1, (A = K, Rb); Ag-tube, 600°C, 14 d] we obtained Rb₂Na₄[Co₂O₅] and K₂Na₄[Co₂O₅] rough, transparent, red single crystals. We find a new type of structure with the anion [O₂CoOCoO₂]^6?. Space group P4₂/mnm; a = 634.4 pm, c = 1030.3 pm, Z = 2 (A = K) a = 647.6 pm, c = 1021.1 pm, Z = 2 (A = Rb); four-circle diffractometer data; MoKα -radiation; 360 from 364 I₀(hkl), R = 4.34%, R_w = 3.54% (A = K); 361 from 366 I₀(hkl), R = 6.54%, R_w = 2.70% (A = Rb). The anion is planar, the CN of Co is 3. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, are calculated and discussed.     

Das erste Diniobat mit ‚isolierten’︁ Anionen: KLi4[NbO5]=K2Li8[Nb2O10]

The First Diniobate with ‘Isolated’ Anions: KLi₄[NbO₅]=K₂Li₈[Nb₂O₁₀] [1] . By heating of well ground mixtures of the binary oxides [K₂O, Li₂O, Nb₂O₅, K:Li:Nb=1.1:4.4:1, Pt-tube, 1100°C, 3d] colourless, triclinic single crystals of KLi₄NbO₅ have been prepared for the first time: space group P1 (Nr. 2) with a=816.9(2) pm, b=592.2(2) pm, c=589.7(2) pm, α=121.00(2)º, β=91.78(2)°, γ=99.23(2)°, Z=2. The crystal structure was solved by four-cycle diffractometer data [Mo-Kα , 1386 from 1386 I_o(hkl), R=3.4%, R_w=2.6%], parameters see text. Characteristic for this structure are “isolated” groups of [Nb₂O₁₀] and the tetrahedral coordination of Li(1), Li(2), and Li(3). Li(4) has a tetragonal-pyramidal coordination. The structural relations are deduced by Schlegel Diagrams. The Madelung Part of Lattice Energy, MAPLE, the Effective Coordination Numbers, ECoN and the charge distribution have been calculated and discussed.     

Sm2As4O9: Ein ungewöhnliches Samarium(III)‐Oxoarsenat(III) gemäß Sm4[As2O5]2[As4O8]

Sm₂As₄O₉: An Unusual Samarium(III) Oxoarsenate(III) According to Sm₄[As₂O₅]₂[As₄O₈] Pale yellow single crystals of the new samarium(III) oxoarsenate(III) with the composition Sm₄As₈O₁₈ were obtained by a typical solid‐state reaction between Sm₂O₃ and As₂O₃ using CsCl and SmCl₃ as fluxing agents. The compound crystallizes in the triclinic crystal system with the space group (No. 2, Z = 2; a = 681.12(5), b = 757.59(6), c = 953.97(8) pm, α = 96.623(7), β = 103.751(7), γ = 104.400(7)°). The crystal structure of samarium(III) oxoarsenate(III) with the formula type Sm₄[As₂O₅]₂[As₄O₈] (≡ 2 × Sm₂As₄O₉) contains two crystallographically different Sm³⁺ cations, where (Sm1)³⁺ is coordinated by eight, but (Sm2)³⁺ by nine oxygen atoms. Two different discrete oxoarsenate(III) anions are present in the crystal structure, namely [As₂O₅]^4? and [As₄O₈]^4?. The [As₂O₅]^4? anion is built up of two Ψ¹‐tetrahedra [AsO₃]^3? with a common corner, whereas the [As₄O₈]^4? anion consists of four Ψ¹‐tetrahedra with ring‐shaped vertex‐connected [AsO₃]^3? pyramids. Thus at all four crystallographically different As³⁺ cations stereochemically active non‐binding electron pairs (“lone pairs”) are observed. These “lone pairs” direct towards the center of empty channels running parallel to [010] in the overall structure, where these “empty channels” being formed by the linkage of layers with the ecliptically conformed [As₂O₅]^4? anions and the stair‐like shaped [As₄O₈]^4? rings via common oxygen atoms (O1 – O6, O8 and O9). The oxygen‐atom type O7, however, belongs only to the cyclo‐[As₄O₈]^4? unit as one of the two different corner‐sharing oxygen atoms.     

Synthese,Kristallstrukturen und Absorptionsspektren der neuen „Cupriosilicate”︁: K6[CuSi2O8] und Rb4[CuSi2O7]

Synthesis, Crystal Structures, and Absorption Spectra of the New “Cupriosilicates”: K₆[CuSi₂O₈] and Rb₄[CuSi₂O₇] K₆[CuSi₂O₈] and Rb₄[CuSi₂O₇] were obtained by annealing intimate mixtures of K₂O and Rb₂O, respectively, CuO and SiO₂ in sealed Ag cylinders at 500°C as transparent greenish-blue single crystals. The structure solution (IPDS-data Mo Kα; K₆[CuSi₂O₈]: 1292 F²(hkl), R1 = 0.059; wR2 = 0.103 and Rb₄[CuSi₂O₇]: 763 F²(hkl), R1 = 0.049; wR2 = 0.114) confirms the space group P1 for both compounds. K₆[CuSi₂O₈]: a = 619.4(2); b = 665.5(2); c = 753.0(2) pm; α = 83.66(3); β = 87.71(3); γ = 70.19(3)°; Z = 1. Rb₄[CuSi₂O₇]: a = 631.9(9); b = 707.5(10); c = 715.2(6) pm; α = 114.2(1); β = 100.7(1); γ = 107.9(1)°; Z = 1. The Madelung Part of the Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these calculated via Mean Effective Ionic Radii, MEFIR, are given. The absorption spectra of K₆[CuSi₂O₈] and Rb₄[CuSi₂O₇] are discussed in terms of the Angular Overlap Model, AOM.