Neue Alkalioxoarsenate (V) Zur Kenntnis von Rb2Li[AsO4] und Cs2Li[AsO4]

New Alkalioxoarsenates (V). On Rb₂Li[AsO₄] and Cs₂Li[AsO₄] By heating of well-grounded mixtures of the binary oxides (A₂O, Li₂O₂, and As₂O₃; A : Li : As = 2 : 1 : 1; Ni-tube, 550°C, 21 d; A = Rb, Cs) colourless single crystals of Rb₂Li[AsO₄] and Cs₂Li[AsO₄] were obtained for the first time. These new orthoarsenates(V) crystalize orthorhombic (space group C mc2₁? C, No. 36) with Z = 4. As expected they are isotypic with the according orthovanadates(V) [2] A₂Li[VO₄], A = Rb, Cs. The lattice constants of Rb₂Li[AsO₄]: a = 582.1(4) pm, b = 1171.1(7) pm, c = 792.4(5) pm and Cs₂Li[AsO₄]: a = 596.4(2) pm, b = 1223.4(2) pm, c = 819.7(3) pm were taken from Guinier-Simon powder data. The structure was determined by four-circle-diffractometer data [Siemens AED II, MoKα , 6290 I₀ (hkl), R = 3.5%, R_w = 3.2% to Rb₂Li[AsO₄]; 3518 I₀ (hkl), R = 2.8%, R_w = 2.6% to Cs₂Li[AsO₄]; parameters see text]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these calculated via Mean Fictive Ionic Radii, MEFIR, as well as charge distribution CHARDI are calculated and discussed.     

Das erste „Lithovanadat”︁: K2{LiVO4}.

The First ?Lithovanadate”?: K₂{LiVO₄} By heating of well ground mixtures of the binary oxides [K₂O, Li₂O, V₂O₅, K:Li: V = 2.2:1.1:1.0; Ni-tube, 900°C, 46 d] colourless monoclinic single crystals of K₂[LiVO₄] have been prepared for the first time: space group C2/m; a = 835.7(1) pm, b = 774.5(1) pm, c = 753,3(1) pm, β = 90.23(1)°. The structure was determined by four-circle diffractometer data [MoKα, 1018 form 1262 I₀ (hkl), R = 8.65%, R_w = 5.67%], 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.     

Über Cs2Li2[GeO4]

About Cs₂Li₂[GeO₄] By heating of a well-ground mixture of the binary oxides CsO_0.55, Li₂O and GeO₂ (Cs:Li:Ge=2,6:2,2:1; Ni-tube; 600 °C; 49d) we got single crystals of Cs₂Li₂[GeO₄] for the first time. Cs₂Li₂[GeO₄] is isotypic to Rb₂Li₂[MO₄] [M = Si, Ti, Ge] [2] and Cs₂Li₂[MO₄] (M = Si, Ti) [3]: according to this Cs₂Li₂[GeO₄] crystallizes triclinic, in the spacegroup P1 with a = 968.7(4) pm, b = 586.0(2) pm, c = 571.4(2) pm, α = 92.71(4)°, β = 110.95(3)° and γ = 94.34(4)° (Guinier-Simon data), Z = 2. The structure was determined by four-circle diffractometer data (Ag? K_α ; 2381 I_o(hkl); R = 8,4%; R_w = 5.0%), parameters see text. Further the Madelung Part of Lattice Energy (MAPLE), Effective Coordination Numbers (ECoN) and the Mean Fictive Ionic Radii (MEFIR), have been 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.     

Neue Metalloxide mit Tetraeder-Doppel als Baugruppe: Rb6[Tl2O6] und Cs6[In2O6]

New Metal Oxides with Doubles of Tetrahedra as Building Units: Rb₆[Tl₂O₆] and Cs₆[In₂O₆] We prepared the hitherto unknown Rb₆[Tl₂O₆] and Cs₆[In₂O₆] by heating mixtures of Tl₂O₃ and RbO_0.60 (Rb:Tl = 3.5:1) as well as In₂O₃ and CsO_0.53 (Cs:In = 3.5:1) as single crystals [closed Ag-cylinder, 650°C, 14 d]. The single crystals of Rb₆[Tl₂O₆] are yellow, those of Cs₆[In₂O₆] pale yellow, all transparent and rude. The new type of structure was elucidated by 4-circle-diffractometer (PW 1100) data. Rb₆[Tl₂O₆]: P2₁/a; a = 1145,7(3), b = 713,3(1), c = 783,9(2) pm, β = 93,73° (2), Z = 2; Ag–Kα, 2100 out of 2531 I₀(hkl), R = 9,6% and R_w = 8,9%. Cs₆[In₂O₆]: P2₁/a; a = 1178,5(4), b = 730,7(2), c = 816,3(2) pm, β = 95,38° (3), Z = 2; Mo–Kα, 1584 out of 2032 I₀(hkl), R = 9,25%, and R_w = 8,44%. The Madelung Part of Lattice Energy, MAPLE, is calculated and 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].     

Cs4[IrO4], ein neues Iridat mit planarem Anion [IrO4]4−

Cs₄[IrO₄], a New Iridate with Planar Anion [IrO₄]^4? For the first time we obtained black single crystals of Cs₄[IrO₄] by heating intimate mixtures of CsO_0.52 and IrO₂ (molar ratio Cs : Ir = 4.30 : 1.00; “Ag-bomb”, 740°C/86 d). Cs₄[IrO₄] crystallizes monocline, C 2/m, with a = 1031.66(8) pm, b = 671.61(4) pm, c = 660.44(6) pm, b? = 108.118(7)° and Z = 2 in the K₄[IrO₄]-type. The structure has been determined by four-circle-diffractometer data (PW 1100 from Phillips, Ag? Kα , graphite) with 841 I₀(hkl) with I ≥ 3s?(F) (from 947 I₀(hkl) out of 3529 measured reflexes). The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Zur Konstitution von Cs2[FeO4]

On the Constitution of Cs₂[FeO₄] For the first time black, spherical single crystals of Cs₂[FeO₄] were prepared by an “oxydative exchange reaction” of NaFeO₂ with CsO_1,8 (molar ratio Fe:Cs = 1.00:2.10, Au-tube, 250°C 3d, 480°C 24d, 360°C 5d): Spacegroup Pnma with a = 842.86(12) pm, b = 628.12(10) pm, c = 1105.33(17) pm. Cs₂[FeO₄] is isotypic to β-K₂SO₄. The structure was determined by four circle diffractometer data [MoKα , 1384 of 1387 I_o(hkl), R = 3.36%, R_w = 3.08%]; parameters as given in the text. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, and the Charge-distribution will be calculated and discussed.     

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].     

Ein Oxostannat neuen Strukturtyps: Cs4[SnO4]

An Oxostannate of a New Structure Type: Cs₄[SnO₄] In order to prepare Cs₃LiSnO₄ by heating of a well ground mixture of the binary oxides [CsO_0.67, Li₂O, SnO₂; Cs:Li:Sn = 3.3:1.0:1.0; 450°C; 28 d; Ni-tube] colourless, monoclinic single crystals of Cs₄[SnO₄] have been yielded for the first time: space group P2₁/c with a = 1180.8 pm. b = 728.2 pm, c = 1166,7 pm, β = 111.79°, Z = 4. The crystal structure was solved by fourcycle-diffractometer data [Siemens AED2, 2299 from 2708 I₀(hkl), R = 7.0%, R_w = 5.6%], parameters see text. Characteristic for the complicated structure are “isolated” [SnO₄]^4? tetrahedra. Mean Fictive Ionic Radii, MEFIR, Effective Coordination Numbers, ECoN and the Madelung Part of Lattice Energy, MAPLE, have been calculated.     

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.     

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.     

Neue Oxoferrate(III). Na2Li3[FeO4] und K2Li3[FeO4]

New Oxoferrates (III). Na₂Li₃[FeO₄] and K₂Li₃[FeO₄] . Na₂Li₃[FeO₄] and K₂Li₃[FeO₄] (transparent, pink or light yellow single crystals) have been prepared by heating mixtures of the oxides (Na:Li:Fe = 2.2:3.3:1; Ag-tube, 720°C, 27 d or K:Li:Fe = 2.2:3.3:1; analogous, 700°C, 40 d). Na₂Li₃[FeO₄] is isotypic with Na₂Li₃[GaO₄] (a = 832.2(1), b = 796.0(1), c = 656.3(1)pm, Pnnm) and K₂Li₃[FeO₄] with K₂Li₃[GaO₄] (a = 557.7(1), b = 880.6(1), c = 1101.8(2)pm, β = 111.51(2)°, P2₁/c). Four cycle diffractometer data: MoK_α, 525 out of 686 I₀(hkl), R = 9.36%, R_w = 5.97% or 1424 out of 1424 I₀(hkl), R = 8.45%, R_w = 5.66%. Parameters see text. The structures are characterized by calculations of the Madelung Part of Lattice Energy, MAPLE. The Effective Coordination Numbers, ECoN, which are calculated by means of Mean Fictive Ionic Radii, MEFIR, are compared with the analogous gallates.     

Ein neues Oxouranat(VI): K2Li4[UO6]. Mit einer Bemerkung über Rb2Li4[UO6] und Cs2Li4UO6

A New Oxouranate(VI): K₂Li₄[UO₆]. With a Remark about Rb₂Li₄[UO₆] and Cs₂Li₄[UO₆] For the first time K₂Li₄UO₆ has been prepared by an exchange reaction of α-Li₆UO₆ with K₂O [K:U = 2.0:1, sealed au-tube; 750°C; 30 d single crystals; 680°C, 10 d powder]. The irregular shaped single crystals, which are of yellow color and sensitive to moisture crystallize in P3 m1 (Z = 1) with a = 619.27(5), c = 533.76(6) pm. The structure determination (PW 1100, AgKα R = 4.80%, R_w = 4.81% for 220 unique reflexions) reveals a new type of structure. The characteristic elements are the isolated group [UO₆] and the C.N. = 12 for K⁺. While Li(1) has a nearly regular square of 4 O^2? as coordination polyhedron, Li(2) is octahedrally surrounded. The Madelung Part of Lattice Energy (MAPLE) is calculated and discussed. In addition to K₂Li₄[UO₆] the new oxides Rb₂Li₄[UO₆] and Cs₂Li₄[UO₆] are prepared as pale yellow powders which are little sensitive to moisture (both: au-tube, 680°C, 10 d). According to powder datas both compounds are isotypic with K₂Li₄[UO₆] [Rb₂Li₄[UO₆]: a = 622.91(5), c = 535.93(6) pm; Cs₂Li₄[UO₆]: a = 626.70(6), c = 539.92(6) pm].     

Über „Gemischt-Koordinierte”︁ einkernige Anionen. 2. Ein Oxoruthenat(VI) neuen Typs: CsK5Ru2O9 = CsK5[RuO5][RuO4]

On ?Mixed-coordinated”? isolated Anions. 2. A New Type of Oxoruthenates(VI): CsK₅Ru₂O₉ = CsK₅[RuO₅][RuO₄] By heating of intimate mixtures of the oxides [KO_1.1, CsO_1.2, RuO₂; K:Cs:Ru = 2.2:1:1; Ag-tube, 750°C, 34d] dark-green single crystals of CsK₅Ru₂O₉ = CsK₅[RuO₅][RuO₄] were obtained for the first time. Ru⁶⁺ shows two different polyhedra in this oxide (tetrahedron, trigonal bipyramid). Untill now Rb₆[TeO₅][TeO₄] [1] next to ?Mg₄GeO₆”? [3] and the isotypic high-pressure silicate [4] was the only examples known. The structure was determined by four-circle diffractometer data [Mo? Kα , 1824 from 1949 I₀(hkl), SG: Pnma, R equals; 12.6%, R_w = 4.5%], parameters see text. Guinier-Simon data gave a = 1701.6(3), b = 827.6(1), c = 905.7(1) pm, Z = 4. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these calculated via Mean Fictive Ionic Radii, MEFIR, were calculated and discussed.     

Neue Oxozincate mit Inselstruktur: K4[ZnO3] Mit einem Anhang über Rb7Na[ZnO3]2

New Nesozincates: K₄[ZnO₃], Rb₇Na[ZnO₃]₂ For the first time A) K₄[ZnO₃] and B) Rb₇Na[ZnO₃]₂ have been prepared (from the binary oxides). They represent the first oxozincates of the alkali metals in which the coordination number of Zn²⁺ is exclusively 3 (carbonate-like groups [ZnO₃]). Both oxides crystallize triclinic, space group P1 with A): a = 1103.3(3), b = 881.3(3), c = 698.2(2) pm, α = 109.65(2)°, β = 89.56(2)°, γ = 102.41(3)° and Z = 4, and B): a = 1128.3(3), b = 974.5(3), c = 711,8(2) pm, α = 114.12(2)β, = = 88.46(3)°,γ = 106.48(2)° and Z = 4. Their crystal structures have been determined from single crystal data (four circle diffractometer) and refined to R = 10.1%, R_w = 7.8% (2905 unique I₀(hkl)) and R = 19.5%, R_w = 17.3% (2269 unique I₀(hkl)), respectively. The Madelung Part of Lattice Energy (MAPLE), Effective Coordination Numbers (ECoN) and Mean Fictive Ionic Radii (MEFIR) have been calculated.     

Über quaternäre Oxoplumbate(IV). Zur Kenntnis von Rb2Li14[Pb3O14] und Cs2Li14[Pb3O14]

On Quaternary Oxoplumbates(IV). On the Knowledge of Rb₂Li₁₄[Pb₃O₁₄] and Cs₂Li₁₄[Pb₃O₁₄] For the first time, Rb₂Li₁₄[Pb₃O₁₄] and Cs₂Li₁₄[Pb₃O₁₄] have been prepared by heating of mixtures of Li₂O, β-?PbO₂”? and Rb₂PbO₃, Cs₂PbO₃ respectively with Li:Pb:A = 14:3:2, (A = Rb, Cs). [Ag-cylinders, sealed under vacuum in Duran-glass ampoule, 590 and 550°C, 40 d, powder (650°C, 200 d, single crystals of Rb₂Li₁₄[Pb₃O₁₄])]. Rb₂Li₁₄[Pb₃O₁₄] is nearly colourless with ivory nuance, Cs₂Li₁₄[Pb₃O₁₄] is pale yellow. According to powder and single crystal investigations, both are isotypic with K₂Li₁₄[Pb₃O₁₄]. Structure refinement of Rb₂Li₁₄[Pb₃O₁₄]: 1015 symmetry independent reflexions, four-circle-diffraktometer PW 1100 (Fa. Philips), ω-scan, MoKα, R = 5.73%, R_W = 5.33%, absorption not considered, space group Immm with a = 1284.71(9), b = 793.90(4), c = 727,35(5) pm, d_x-ray = 4.99 g · cm^?3, d_pyc = 5.01 g · cm^?3, Z = 2. Cs₂Li₁₄[Pb₃O₁₄]: a = 1295.28(12), b = 796.69(8), c = 732.44(7) pm, d_x-ray = 5.31 g · cm^?3, d_pyc = 5.28 g · cm^?3, Z = 2. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Effective Ionic Radii, MEFIR, are calculated.     

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.     

Das erste gemischt-valente Oxocobaltat(I,II): Rb5Co2O4 [1]

A New Mixed-Valent Oxide of Cobalt(I, II): Rb₅Co₂O₄ For the first time we obtained a new mixed-valent oxide of mono- and divalent Cobalt. Black-red single-crystals of Rb₅Co₂O₄ were prepared by heating powders of “Rb₆CdO₄” in closed Co-cylinders at 500° during 48 days. Structure solution and refinement are covered by two measurements with four-circle diffractometers. MoKα : 2 145 I_o(hkl), out of 2 818 I_o(hkl), R = 9.85%, R_w = 5.93% AgKα : 1 813 I_o(hkl) out of 4 007 I_o(hkl), R = 9.46%, R_w = 6.51%) and confirm the space-group P1 . The lattice constants are a = 696.4(1) pm, b = 922.2(3) pm, c = 958.9(3) pm , α = 117.99(2)°, β = 89.96(2)°, γ h= 108.12(2)°, Z = 2 According to its composition Rb₁₀[OCoO]₂[OCoO₂CoO] the structure is built up by two Co atoms of chemically and crystallographically different nature. We find isolated dumb-bell-like anions [O? Co? O]^3? being already known with monovalent Co (e. g. K₃CoO₂) together with units [OCoO₂CoO]^4? of two connected triangles CoO₃ being well-known from K₂BeO₂ ? K₄[Be₂O₄]. ECoN/mEFIR calculations are made starting with values obtained by a new procedure called “MEFIR-FIT”.     

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.