Über Hexafluoroferrate(III): Cs2TlFeF6, Cs2KFeF6, Rb2KFeF6, Rb2NaFeF6 und Cs2NaFeF6

On Hexafluoroferrates(III): Cs₂TlFeF₆, Cs₂KFeF₆, Rb₂KFeF₆, Rb₂NaFeF₆, and Cs₂NaFeF₆ New prepared are the compounds Cs₂TlFeF₆ (a = 9.21₁ Å), Cs₂KFeF₆ (a = 9.04₁ Å), Rb₂KFeF₆ (a = 8.86₈ Å) and Rb₂NaFeF₆ (a = 8.46 ₄Å) all cubic Elpasolithes as well as Cs₂NaFeF₆ (Cs₂NaCrF₆?type, hexagonal with a = 6.28₁, c = 30.53₂ Å), all colourless. Cs₂KFeF₆ was measured magnetically (70–297,2 K). The spectra of reflection were measured (9000–36000 cm^?1). The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.     

Neue Hexafluoromolybdate(III). Cs2MMoF6, Rb2MMoF6, TI2MMoF6 (M = K,Na) und Cs2TIMof6. Mit einer Notiz über MoF3

Novel Hexafluoromolybdates(III): Cs₂MMoF₆, Rb₂MMoF₆, TI₂MMoF₆ (M = K, Na), and Cs₂TIMoF₆. With a Notice on MoF₃ MoF3, light yellow, hexag., a = b = 5.21, c = 14.41 Å, pure prepared by a new method, forms at higher temperatures with the corresponding Fluorides AF the hitherto unknown compounds Cs₂KMoF₆ (a = 9.2₀ Å), Cs₂TlMoF₆ (a = 9.39₂ Å). Rb₂KMoF₆ (a = 8.91₁ Å), Rb₂NaMoF₆ (a = 8.63₂ Å), Tl₂KMoF₆ (a = 8,97₇ Å), Tl₂NaMoF₆ (a = 8.64₉ Å) and K₂NaMoF₆ (a = 8.50₁ Å), all cubic Elpasolithes and all light yellow. The magnetic properties of MoF₃ (100.4–295.2 K) and Tl₂NaMoF₆ (81.4–251.3 K) are investigated. The spectra of reflection were measured (15000–36000 cm^?1). The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.     

Über Hexafluorovanadate(III). Cs2MVF6 und Rb2MVF6 (MTl,K und Na); mit einer Bemerkung über Na3VF6

On Hexafluorovanadates(III). Cs₂MVF₆ and Rb₂MVF₆ (M?Tl, K. and Na); with a Remark on Na₃VF₆ By heating the binary fluorides in a closed system we obtained Cs₂TlVF₆ (a = 9.23₄ Å), Cs₂KVF₆ (a = 9.04₇ Å), Rb₂KVF₆ (a = 8.85₅ Å) and Rb₂NaVF₆ (a = 8.46₈ Å), all cubic Elpasolithes of soft green colour as well as Cs₂NaVF₆ (hexagonal a = 6.24 Å, c = 30.58 Å, isotypic with Cs₂NaCrF₆) and Na₃VF₆ (monoclinic a = 5.51₃ Å, b = 5.72₁ Å, c = 7.96₃ Å, β = 90.4₇°, isotypic with Na₃AlF₆). VF₃ (3.0–296.2°K), Cs₂TlVF₆, Cs₂KVF₆ and Rb₂KVF₆ (all from 70–299°K) have been measured magnetically. The spectra of reflection in the range of 9 000 to 33 000 cm^?1 of VF₃ and the new quaternary fluorides are measured and discussed. The Madelung Part of Lattice Energy (MAPLE) is calculated and discussed.     

Uber Hexafluorotitanate (III). Cs2MTiF6 und Rb2MTiF6 (M  K bzw. Na); mit einer Bemerkung über Tl3TiF6

On Hexafluorotitantes (III). Cs₂MTIF₄ and Rb₂MTIF₄(M?K, Na); with a Remark on TI₃TIF₆ By heating the binary fluorides in a closed system we obtained Cs₂KTiF₆ (a = 9.12₄ Å), Rb₂KTiF₆ (a = 8.93₂ Å) and Rb₂NaTiF₆ (a = 8.53₃ Å), all cubic Elpasolithes of light blue colour as well as Cs₂NaTiF₆ (hexagonal a = 6.27₂, c = 30.91 Å, isotypic with Cs₂NaCrF₆) and Tl₃TiF₆ TiF₃ (3.1–295.5°K) and Cs₂KTiF₆ (74.9–297.7°K) have been measured magnetically. The spectra of reflection in the range of 10 000 to 30 000 cm^?1 of TiF₃ and the new quaternary fluorides are similar. The Madelung Part of Lattice Energy (MAPLE) is calculated and discussed.     

Zur Kenntnis der Hexafluororhodate(III): Über Cs2K[RhF6], Rb2K[RhF6], K2Na[RhF6], Rb2Na[RhF6] und Tl2Na[RhF6]

On the Knowledge of Hexafluororhodates(III): Cs₂K[RhF₆], Rb₂K[RhF₆], K₂Na[RhF₆], Rb₂Na[RhF₆] and Tl₂Na[RhF₆]. New prepared are the compounds Cs₂KRhF₆ (a = 9.04₉ Å), Rb₂NaRhF₆ (a = 8.49₂ Å), Rb₂KRhF₆ (a = 8.87₆ Å), K₂NaRhF₆ (a = 8.36₂ Å) and Tl₂NaRhF₆ (a = 8.52₆ Å), all cubic Elpasoliths of pink colour. The Madelung-Part of lattice energy, MAPLE, is calculated and discussed.     

Die Kristallstruktur von Cs2PrO3, sowie über Cs2CeO3, Cs2TbO3, Rb2CeO3 und Rb2TbO3

Crystal Structure of Cs₂PrO₃ and also about Cs₂CeO₃, Cs₂TbO₃, Rb₂CeO₃, and Rb₂TbO₃ New prepared Cs₂PrO₃ (dark brown) is orthorhombic due to single crystal data, K₂PbO₃ type of structure (Cmc2₁) with a = 11.4₇, b = 7.72₂, c = 6.42₇ Å and Z = (4). Cs₂CeO₃ (colourless, a = 11.49₅, b = 7.75₃, c = 6.43₇ Å), Cs₂TbO₃ (red-brown, a = 11.3₇, b = 7.72₆, c = 6.14₂ Å), and the low-temperature form of (LT-) Rb₂TbO₃ (red-brown, a = 10.9₁, b = 7.39₀, c = 6.09₉ Å) are isotypic. Hitherto unknown HT-Rb₂CeO₃ (high-temperature form, colourless, a = 3.83₇, c = 18.4₇ Å, Z = 2, hexagonal) and “HT-Rb₂TbO₃” (red-brown, a = 3.77₃, c = 18.0₀ Å) correspond according to powder-data to the α-NaFeO₂ type of structure. Cs₂PrO₃ has been measured magnetically (100–300 K). The Madelung Part of Lattice Energy (MAPLE) is calculated and discussed.     

Goldreiche Auride mit Caesium: Cs1,34Rb0,66RbAu7 und Cs1,60Rb0,40RbAu7

Gold-rich Aurides with Caesium: Cs_1.34Rb_0.66RbAu₇ and Cs_1.60Rb_0.40RbAu₇ Cs_1,60Rb_0,40RbAu₇, Raumgruppe Cmmm, Z = 2, a = 5,677(1) Å, b = 13,273(3) Å, c = 7,288(1) Å, R1/wR2 = 0,0392/0,0892, Z(F) ≥ 2σ(F) = 700 and Z(Var.) = 23. Silver coloured, brittle single crystals of Cs_1.34Rb_0.66RbAu₇ and Cs_1.60Rb_0.40RbAu₇ were obtained by the reaction of CsN₃, RbN₃ and gold sponge at 903 K. The structures were determined from X-ray single-crystal diffractometry data: Cs_1.34Rb_0.66RbAu₇, space group Cmmm, Z = 2, a = 5.657(1) Å, b = 13.265(4) Å, c = 7.281(2) Å, R1/wR2 = 0.0373/0,0628, N(F) ≥ 2σ(F) = 818 and N(var.) = 23.     

Neues über K2[MnF6], Rb2[MnF6] und Cs2[MnF6]

News on K₂[MnF₆], Rb₂[MnF₆], and Cs₂[MnF₆] Cs₂[MnF₆] (a = 8.97₂ Å) and Rb₂[MnF₆] (a = 8.53₁ Å) as well as this with K₂[MnF₆] (a = 8.22₁ Å and hexagonal a = 5.72₂, c = 9.33₁ Å) form mixed crystals of the K₂PtCl₆ type of structure. Calculations of the Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, lead contrary to former assumptions to distances Mn? F of about 1.86 Å (CN 6).     

Über Hexafluoroindate(III): A2TllnF6 (A=Rb,Cs), (RbTI)BlnF6 (B= Na,Ag, K) und A2AglnF6 (A=Rb,TI,Cs)

On Hexafluoroindates(II1): A₂TlInF₆ (A = Rb, Cs), (RbTI)BInF₆ (B = Na, Ag, K), and A₂AgInF₆ (A = Rb, TI, Cs) By heating the binary components in a closed system are new prepared the compounds Rb₂AgInF₆, Rb₂CsInF₆, (RbTl)NaInF₆ (RbTI)AgInF₆, (RbTI)KInF₆, Tl₂AgInF₆, Cs₂AgInF₆ and Cs₂TlInF₆, all cubic, colourless Elpasolithes, as well as Rb₂TlInF₆, according to powder photographs tetragonal. The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.     

Drei neue Selenoborato-closo-dodekaborate: Synthesen und Kristallstrukturen von Rb8[B12(BSe3)6], Rb4Hg2[B12(BSe3)6] und Cs4Hg2[B12(BSe3)6]

Three Novel Selenoborato- closo -dodecaborates: Syntheses and Crystal Structures of Rb₈[B₁₂(BSe₃)₆], Rb₄Hg₂[B₁₂(BSe₃)₆], and Cs₄Hg₂[B₁₂(BSe₃)₆] The three selenoborates Rb₈[B₁₂(BSe₃)₆] (P1, a = 10.512(5) Å, b = 10.450(3) Å, c = 10.946(4) Å, α = 104.53(3)°, β = 91.16(3)°, γ = 109.11(3)°, Z = 1), Cs₄Hg₂[B₁₂(BSe₃)₆] (P1, a = 9.860(2) Å, b = 10.740(2) Å, c = 11.078(2) Å, α = 99.94(3)°, β = 90.81(3)°, γ = 115.97(3)°, Z = 1), and Rb₄Hg₂[B₁₂(BSe₃)₆] (P1, a = 9.593(2) Å, b = 10.458(2) Å, c = 11.131(2) Å, α = 99.25(3)°, β = 91.16(3)°, γ = 116.30(3)°, Z = 1) were prepared from the metal selenides, amorphous boron and selenium by solid state reactions at 700 °C. These new chalcogenoborates contain B₁₂ icosahedra completely saturated with six trigonal-planar BSe₃ entities functioning as bidentate ligands to form a persubstituted closo-dodecaborate anion. The two isotypic compounds Rb₄Hg₂[B₁₂(BSe₃)₆] and Cs₄Hg₂[B₁₂(BSe₃)₆] are the first selenoborate structures containing a transition metal which are characterized by single crystal diffraction.     

Über Oxoniccolate(II) der Alkalimetalle:K2NiO2, Rb2NiO2 und Cs2NiO2

On Oxoniccolates(II) of Alkali Metals: K₂NiO₂, Rb₂NiO₂, and Cs₂SiO₂. The hitherto unknown K₂NiO₂ (dichroic single crystals: redviolet/green, a=3.95₃, c=12.85₃ Å), Rb₂NiO₂ (analogous yellowred/green, a=4.17₄, c=13.18₆ Å) and Cs₂NiO₂ (analogous: darkgreen/green, a=4.41₃, c=13.59₀ Å) have been obtained, which surprisingly crystallize in the tetragonal Na₂HgO₂-type of structure with [O–-Xi –-O]-dump-bells. The distance Ni –-O is very short: 1.68 Å. The K₂SiO₂-structure was determined using single crystal data, R=7.98% and R′=10.6% for 131 reflections hhl–- (h+3)hl. The magnetic datas for K₂NiO₂ and Cs₂NiO₂ obey the CURIE -WEISS -law (μ=3,0 μ_B. Θ ? ?30°K). The Madelung Part of Lattice Energy (MAPLE) is calculated and discussed.     

Neue Fluorperowskite mit Cr‴ und Mn‴: A(B03Cr0.5)F3 und A(B05Mn0,5)F3; A,B=Alkalimetall

New fluoroperovskites with Cr^III and Mn^III: A(B_0.5Cr_0.5)F₃ and A(B_0.5Mn_0.5)F₃; A, B = alkali We obtained Cs₂KCrF₆ (a = 9.00₄ Å), Rb₂KCrF₆ (a = 8.81₇ Å), Rb₂NaCrF_e(a = 8.41₈ Å) (all green, K₂NaCrF₆-type) and Cs₂NaCrF₈ as well as Rb₂NaMnF₆ (tetragonally distorted K₂NaCrF₆-type; a = 8.36₅, c = 8.66₀ Å; F4/mmm), and Rb₂KMnF₆ and Cs₂NaMnF₆, all violet. Jahn-Teller-distortion and lattice energy of Rb₂NaMnF₆ and K₂NaMnF₆ are discussed.     

One‐Dimensional Zinc Selenophosphates: A2ZnP2Se6 (A = K,Rb, Cs)

The new compounds A₂ZnP₂Se₆ (A = K, Rb, Cs) were synthesized via molten salt flux syntheses. The crystals feature one‐dimensional ¹/_∞[ZnP₂Se₆]^2– chains charge balanced by alkali metal ions between the chains. K₂ZnP₂Se₆ crystallizes in the monoclinic space group P2₁/c; cell parameters a = 12.537(3) Å, b = 7.2742(14) Å, c = 14.164(3) Å, β = 109.63(3)°, Z = 4, and V = 1216.7(4) ų. Rb₂ZnP₂Se₆ and Cs₂ZnP₂Se₆ are isotypic, crystallizing in the triclinic space group P$\bar{1}$ . Rb₂ZnP₂Se₆ has cell parameters of a = 7.4944(15) Å, b = 7.6013(15) Å, c = 12.729(3) Å, α = 96.57(3)°, β = 105.52(3)°, γ = 110.54(3)°, Z = 2, and V = 636.6(2) ų. Cs₂ZnP₂Se₆ has cell parameters of a = 7.6543(6) Å, b = 7.7006(6) Å, c = 12.7373(11) Å, α = 97.007(7)°, β = 104.335(7)°, γ = 109.241(6)°, Z = 2, and V = 669.54(10) ų.     

Neue Oxoplumbate(II) A2PbO2 (A = K,Rb, Cs) mit zweikernigen Gruppen [OPbO2PbO]

New Oxoplumbates(II) A₂PbO₂ (A = K, Rb, Cs), with Binuclear Groups [OPbO₂PbO] Unknown K₂PbO₂, Rb₂PbO₂ and Cs₂PbO₂ (yellowish powder, yellowish transparent single crystals, respectively) have been prepared, The compounds crystallize triclinic with a = 10.90₁ Å, b = 7.60₆ Å, c = 7.32₈ Å, α = 119.3₅°, β = 88.4₂°, γ =117,7₃°, (K₂PbO₂); a = 10.90₇ Å, b = 8.51₀ Å, c = 7.81₅ Å, α = 124.0₀°, β = 84.9₇°, γ = 120.6₈° (Rb₂PbO₂) and a = 11.64₄ Å, b = 8.90₅ Å, c = 8.04₀ Å, α = 123.3₂°, β = 85.7₀°, γ = 120.4₉° Z = 4, space group P1 -C/_i¹. For K₂PbO₂ we find R = 8.6₅% and R_w = 9.3₂% (2283 independent reflections). Parameters see text. There are isolated [Pb₂O₄]groups, which are connected in a complicated way by mutual K⁺ ions forming layers. The Madelung Part of the Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these by means of mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

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.     

Die Kristallstruktur von Cs2S. mit einer Bemerkung über Cs2Se,Cs2Te,Rb2Se und Rb2Te

The Crystal Structure of Cs₂S and a Remark about Cs₂Se, Cs₂Te, Rb₂Se, and Rb₂Te Cs₂S crystallizes orthorhombic, a = 8.57₁, b = 5.38₃, c = 10.3₉ Å, Z = 4, d_rö = 4.13, d_pyk = 4.19 g · cm^?3, D–Pnma with \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {{\rm Cs}}\limits^|,\mathop {{\rm Cs}}\limits^\parallel $\end{document} and S in 4(c) each, for parameter see text. It is R = 10,4% for 202 of 222 possible reflexes. There is a sequence of S^2? corresponding to the hexagonal closest packing of sphares. Cs occupies half of “tetrahedron” and all “octahedron vacancies”; the deviation of \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {{\rm Cs}}\limits^|, $\end{document} in ?oktahedron vacancies”? is noticeable. Effective Coordination Numbers, ECoN, and the Madelung Part of Lattice Energy, MAPLE, are calculated and discussed.     

Syntheses and Crystal Structures of Rb2B2Se7, Tl2B2Se7, Cs3B3Se10, and Tl3B3Se10: New Perseleno‐selenoborates with Polymeric Anionic Chains

The perseleno‐selenoborates Rb₂B₂Se₇ and Cs₃B₃Se₁₀ were prepared from the metal selenides, amorphous boron and selenium, the thallium perseleno‐selenoborates Tl₂B₂Se₇ and Tl₃B₃Se₁₀ directly from the elements in evacuated carbon coated silica tubes by solid state reactions at temperatures between 920 K and 950 K. All structures were refined from single crystal X‐ray diffraction data. The isotypic perseleno‐selenoborates Rb₂B₂Se₇ and Tl₂B₂Se₇ crystallize in the monoclinic space group I 2/a (No. 15) with lattice parameters a = 12.414(3) Å, b = 7.314(2) Å, c = 14.092(3) Å, β = 107.30(3)°, and Z = 4 for Rb₂B₂Se₇ and a = 11.878(2) Å, b = 7.091(2) Å, c = 13.998(3) Å, β = 108.37(3)° with Z = 4 for Tl₂B₂Se₇. The isotypic perseleno‐selenoborates Cs₃B₃Se₁₀ and Tl₃B₃Se₁₀ crystallize in the triclinic space group P1 (Cs₃B₃Se₁₀: a = 7.583(2) Å, b = 8.464(2) Å, c = 15.276(3) Å, α = 107.03(3)°, β = 89.29(3)°, γ = 101.19(3)°, Z = 2, (non‐conventional setting); Tl₃B₃Se₁₀: a = 7.099(2) Å, b = 8.072(2) Å, c = 14.545(3) Å, α = 105.24(3)°, β = 95.82(3)°, γ = 92.79(3)°, and Z = 2). All crystal structures contain polymeric anionic chains of composition ([B₂Se₇]^2–)_n or ([B₃Se₁₀]^3–)_n formed by spirocyclically fused non‐planar five‐membered B₂Se₃ rings and six‐membered B₂Se₄ rings in a molar ratio of 1 : 1 or 2 : 1, respectively. All boron atoms have tetrahedral coordination with corner‐sharing BSe₄ tetrahedra additionally connected via Se–Se bridges. The cations are situated between three polymeric anionic chains leading to a nine‐fold coordination of the rubidium and thallium cations by selenium in M₂B₂Se₇ (M = Rb, Tl). Coordination numbers of Cs⁺ (Tl⁺) in Cs₃B₃Se₁₀ (Tl₃B₃Se₁₀) are 12(11) and 11(9).     

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.     

Neue Oxozincate der Alkalimetalle: Rb2[ZnO2] und Cs2[ZnO2]

New Oxozineates of Alkali Metals: Rb₂[ZnO₂] and Cs₂[ZnO₂] Colorless single crystals of the hitherto unknown Rb₂[ZnO₂] (a = 9.55₈, b = 6.33₅, c = 15.91 Å, β = 118.6°, z = 8, d_pyk = 4.11, d_rö = 4.21 g · cm^?3) and Cs₂[ZnO₂] (a = 9.85₁, b = 6.61₉, c = 16.26 Å, β = 116.8°) have been prepared, which crystallize monoclinic, P2₁/c – D. (For parameters see text.) Unexpected there are “isolated” groups [Zn₄O₈]. Half of the Zn atoms exhibit the unusual coordination number 3 towards O^2?. The Madelung Part of Lattice Energy, MAPLE, and the Effective Coordination Number, ECoN, the latter by means of Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Über Ordnungsvarianten des NaCl-Typs. Neue kubische Formen von NaMO2 (M=Sc,Y, Dy,Tm, Yb,Lu), K2MO3 Rb2MO3, (M = Ce,Pr, Th) und Cs2ThO3

On Ordered Variants of the NaCl Type of Structure: New Cubic Forms of NaMO₂ (M = Sc, Y, Dy, Tm, Yb, Lu), K₂MO₃, Rb₂MO₃ (M = Ce, Pr, Th), and Cs₂ThO₃ We obtained hithertoo unknown cubic forms of NaScO₂ (a = 4.52₅ Å), NaYO₂ (a = 4.79₁ Å), NaDyO₂ (a = 4.80₀ Å), NaTmO₂ (a = 4.74₃Å), NaYbO₂ (a = 4.73₀ Å), NaLuO₂ (a = 4.71₅ Å) [all colourless], K₂CeO₃ (a = 5.20₃ Å), K₂PrO₃ (a = 5.18₅ Å), K₂ThO₃ (a = 5.30₈ Å), Rb₂CeO₃ (a = 5.39₇ Å), Rb₂PrO₃ (a = 5.36₇ Å), Rb₂ThO₃ (a = 5.47₅ Å), and Cs₂ThO₃ (a = 5.70₄ Å) [colour see ins.] by heating mixtures of the binary oxides AO_x (A = Na, K, Rb, Cs) with active forms of M₂O₃, respectively. It is discussed MO₂, how one may understand the existence of the cubic forms, which according to powder data show a statistical distribution of cations (with different charge and ionic radius).