Die Perthioborate RbBS3, TIBS3 und TI3B3S10

The Perthioborates RbBS₃, TIBS₃, and Tl₃B₃S₁₀ . RbBS₃ (P2₁/c, a=7.082(2) Å, b=11.863(4) Å, c=5.794(2) Å, β=106.54(2)°) was prepared as colourless, plate-shaped crystals by reaction of stoichiometric amounts of rubidium sulfide, boron, and sulfur at 600°C and subsequent annealing. TlBS₃ (P2₁/c, a=6.874(3) Å, b=11.739(3) Å, c=5.775(2) Å, β=113.08(2)°) which is isotypic with RbBS₃ was synthesized from a sample of the composition Tl₂S · 2 B₂S₃. The glassy product which was obtained after 7 h at 850°C was annealed in a two zone furnace for 400 h at 400→350°C. Yellow crystals of TlBS₃ formed at the warmer side of the furnace. Tl₃B₃S₁₀ (P1 , a=6.828(2) Å, b=7.713(2) Å, c=13.769(5) Å, α=104.32(2)°, β=94.03(3)°, γ=94.69(2)°) was prepared as yellow plates from stoichiometric amounts of thallium sulfide, boron, and sulfur at 850°C and subsequent annealing. All compounds contain tetrahedrally coordinated boron. The crystal structures consist of polymeric anion chains. In the case of RbBS₃ and TlBS₃ nonplanar five-membered B₂S₃ rings are spirocyclically connected via the boron atoms. To obtain the anionic structure of Tl₃B₃S₁₀ every third B₂S₃ ring of the polymeric chains of MBS₃ is to be substituted by a six-membered B(S₂)₂B ring.     

Magnetic Structure of CsPd2F5

The structure of CsPd₂F₅ has been confirmed from neutron diffraction data on powdered sample. CsPd₂F₅ crystallizes in the orthorhombic Imma space group. At 100 K, the unit-cell constants are a = 6.473(2) Å, b = 7.853(5) Å, c = 10.718(3) Å and the calculation carried out using the Rietveld method leads to R₁ = 0.020. The network is formed of PdF₆ octahedra chains containing half of Pd in high-spin configuration, connected one to each other by square planes containing the other half of Pd in low-spin configuration. CsPd₂F₅ orders antiferromagnetically below T_N = 38 K. In the ordered state a weak ferromagnetic component occurs (σ₀ = 0.098 μ_B at 2 K). The magnetic structure determined at 4 K is consistent with the magnetization data and can be described in the Im′m′a′ magnetic group without any doubling of the unit-cell parameters. Within the chains, Pd²⁺ are coupled antiparallel. The magnetic moments are located in the (x0z) plane, the angle between the moments and the z axis being 18°.     

Crystal Structure and Ionic Conductivity of Cesium Trifluoromethyl Sulfonate,CsSO3CF3

The crystal structures of the room and the high temperature modifications of cesium trifluoromethyl sulfonate were solved from high resolution X‐ray powder diffraction data. At room temperature, α‐CsSO₃CF₃ crystallizes in the monoclinic space group P2₁ with lattice parameters a = 9.7406(2) Å, b = 6.1640(1) Å, c = 5.4798(1) Å, and β = 104.998(1)°; Z = 2. At temperatures above T = 380 K, a second order phase transformation towards a disordered C‐centered orthorhombic phase in space group Cmcm occurs with lattice parameters at T = 492 K of a = 5.5074(3) Å, b = 19.4346(14) Å, and c = 6.2978(4) Å; Z = 4. Within the crystal structures, the triflate anions are arranged in double layers with the apolar CF₃‐groups pointing towards each other. The cesium ions are located between the SO₃‐groups. CsSO₃CF₃ shows a specific ion conductivity ranging from σ = 1.06·10^?8 Scm^?1 at T = 393 K to σ = 5.18·10^?4 Scm^?1 at T = 519 K.     

Neutron powder diffraction and magnetic measurements on RbTil3, RbVI3, and CsVI3

CsVI₃ (a = 8.124(1) c = 6.774(1)Å,Z = 2, P6₃/mmc at 293 K) adopts the BaNiO₃ structure. Three-dimensional magnetic ordering takes place atT_c = 32(1)K. At 1.2 K the magnetic moment is 1.64(5) μ_B and it forms a 120° spin structure in the basal plane. RbVI₃ (a = 13.863(2) c = 6.807(1) Å,Z = 6, P6₃cmor P3¯c1 at 293 K) and RbTiI₃ (a = 14.024(3) Å,c = 6.796(2) Å,Z = 6, P6₃cm orP3¯c1 at 293 K) adopt a distorted BaNiO₃ structure, probably isostructural with KNiCl₃.T_c of RbVI₃ is 25(1) K. At 1.2 K, RbVI₃ has a spin structure similar to the one of CsVI₃ with a magnetic moment of 1.44(6) μ_B. RbTiI₃ shows no magnetic ordering at 4.2 K. It is shown that a deviation from the 120° structure is expected for compounds with a distorted BaNiO₃ structure such as RbVI₃. The cell dimensions of CsTiI₃ are reported.     

Neutronenpulverdiffraktionsmessungen an [Zn(ND3)4]I2 bei 1,5 K, 10 K und 293 K: Wasserstoff-Brückenbindungen und Bewegungen von ND3-Molekülen

Neutron Powder Diffraction Measurements on [Zn(ND₃)₄]I₂ at 1.5 K, 10 K, and 293 K: Hydrogen Bonds and Dynamic of ND₃ Molecules Microcrystalline powder of [Zn(ND₃)₄]I₂ can be prepared by the reaction of gaseous NH₃ with dry ZnI₂ at room temperature within 8 h. Neutron powder diffraction measurements at 1.5 K, 10 K and 293 K were used to localize all hydrogen atoms. Isolated [Zn(ND₃)₄]²⁺ tetrahedra are three dimensionally linked with 2- and 3-centre (bent and bifurcated) N? D …? I^?-hydrogen bonds. Ammonia molecules are ordered at 1.5 K. Room temperature high thermal displacement parameters for D hint to the fact that NH₃-dynamics take place. Lattice parameters 300 K [10 K; 1,5 K]: a = 10.3783(8) Å [10.3407(4) Å; 10.3381(5)], b = 7.5239(6) Å [7.3960(2) Å; 7.3935(4) Å], c = 13.088(1) Å [12.9731(4) Å; 12.9695(6) Å], space group: Pnma.     

Einkristallstrukturaufklärung und elektronenmikroskopische Untersuchungen an einem neuen Uranniobat: γ-UNbO5

X-Ray Single Crystal and Electron Microscopic Investigations on a New Uranium Niobate: γ-UNbO₅ Black cuboid formed crystals of γ-UNbO₅ were obtained (at T₁) by chemical transport in a temperature gradient (T₂ → T₁; 1000 °C → 980 °C) using UNb₂O₇ as starting material (at T₂) and a combination of NbCl₅ and Cl₂ as transport agent. They were examined by X-rays and electron microscopy. The new modification of γ-UNbO₅ crystallizes orthorhombically (space group Pmma) with a = 7.492(3) Å, b = 4.124(4) Å and c = 6.434(4) Å. The compound is isostructural to UVO₅ and UMoO₅. The crystal structure shows parallel layers formed by edge sharing UO₇ and NbO₆ polyhedra. Polyhedra of neighbouring layers (distance = b) are mutually corner linked.     

Neutron powder diffraction on RbCrl3 and magnetic measurements on RbCrl3 and CsCrl3

β-RbCrI₃ (a = 13.772(3), b = 8.000(2), c = 7.069(2) Å β = 95.85(1)°, $\text{Z = 4,}\text{C2}\text{m}$ at 293 K) and γ-RbCrI₃ (a = 13.586(2), b = 7.923(2), c = 14.094(3) Å, β = 96.88(1)°, Z = 8, C2 at 1.2 K) are isostructural to β-RbCrCl₃ and γ-RbCrCl₃ and are both Jahn-Teller distorted BaNiO₃ structures. In both compounds elongated octahedra occur. γ-RbCrI₃ most probably has a magnetic spiral structure at 4.2 and 1.2 K. Theoretically, a spiral propagating along the b axis is expected. A model with k = 9/19b1 yielded the best result. However, no good fit was obtained possibly because of a misfit in k and canting of the magnetic moments due to anisotropy. χ vs T single-crystal measurements on β-CsCrI₃ are in accordance with its magnetic structure. The three-dimensional magnetic ordering temperature T_c is estimated as 27(1) K. From the χ vs T curves of γ-RbCrI₃, T_c could not be determined. From fits to χ vs T powder data $\text{J}\text{k}$ of CsCrI₃ and RbCrI₃ are estimated to be ?14(2) and ?11(1) K, respectively.     

Structural phase transition,thermal analysis,and spectroscopic studies in an organic–inorganic hybrid crystal: [(CH3)2NH2]2ZnBr4

An organic–inorganic hybrid compound [(CH₃)₂NH₂]₂ZnBr₄ has been prepared at room temperature under the slow evaporation method. Its structure was solved at 150 K using the single-crystal X-ray diffraction method. [(CH₃)₂NH₂]₂ZnBr₄ crystallizes in the monoclinic system – a = 8.5512 (12) Å, b = 11.825 (2) Å, c = 13.499 (2) Å, β = 90.358 (6)°, V = 1365 (4) ų, and Z = 4, space group P2₁/n. In the structure of [(CH₃)₂NH₂]₂ZnBr₄, tetrabromozincate anions are connected to organic cations through N–H⋯ Br hydrogen bonds. Differential scanning calorimetry (DSC) measurements indicate that [(CH₃)₂NH₂]₂ZnBr₄ undergoes four phase transitions at T₁ = 281 K, T₂ = 340 K, T₃ = 377 K, and T₄ = 408 K. Meanwhile, several studies including DSC measurements and variable-temperature structural analyses were performed to reveal the structural phase transition at T = 281 K in [(CH₃)₂NH₂]₂ZnBr₄. Conductivity and dielectric study as a function of temperature (378 < T [K] < 423) and frequency (10⁻¹ < f [Hz] < 10⁶) were investigated. Analysis of equivalent circuit, alternating current conductivity, and dielectric studies confirmed the phase transition at T₄. Conduction takes place by correlated barrier hopping in each phase.     

Ordered Magnetic Frustration. XI. Refinement of the Crystal and Frustrated Magnetic Structures of the Direct Weberite Na2NiCrF7 by Neutron Powder Diffraction

The nuclear and magnetic structures of the ferrimagnetic (T_c = 4 K) weberite Na₂NiCrF₇ were solved by neutron powder diffraction experiments at T>4 K, 2.13 and 1.5 K respectively. The cell is orthorhombic (Space group Imma, a = 7.183(1) Å, b = 10.224(1) Å, c = 7.414(1) Å, Z = 4). The nuclear and the magnetic cells are identical. An anomaly in the thermal variation of the intensity of some magnetic reflections at 2 K is due to the disparity between the thermal variation of the magnetization of the two sublattices of Ni²⁺ and Cr³⁺. The former is already close to its maximum value at 2 K (μ_Ni²⁺ = 1.65(2) μB at 2.13 K and 1.75(2) μB at 1.5 K) whereas the latter continues to increase below this temperature (μ _cr³⁺ = 1.84(5) μB at 2.13 K and 2.22(6) μB at 1.5 K.)     

Co(NH3)2Cl2 and Co(ND3)2Cl2: Order‐Disorder Behaviour of N(H, D)3 and Antiferromagnetic Structure

Diammine cobalt(II) chloride, Co(N(H, D)₃)₂Cl₂ was prepared by decomposition of the corresponding hexaammines at 120 °C in dynamical vacuum. Crystal structures and magnetic properties of these materials were characterised by X‐ray and neutron powder diffraction, and heat capacity measurements. At ambient temperatures Co(N(H, D)₃)₂Cl₂ crystallises in the Cd(NH₃)₂Cl₂ type structure: space group Cmmm, Z = 2, a = 8.0512(2) Å, b = 8.0525(2) Å, c = 3.73318(9) Å (X‐ray data of the H compound). This structure consists of chains of edge‐sharing octahedra [CoCl_4/2(NH₃)₂] running along the c‐axis. Neutron diffraction confirms that that the ND₃ groups are rotationally disordered at ambient temperatures. At 1.5 K and 20 K neutron diffraction data reveal rotational ordering of the ND₃ groups leading to doubling of the c‐axis and to Ibmm symmetry: a = 7.9999(6) Å, b = 7.9911(5) Å, c = 7.4033(3) Å (Z = 4, values for T = 1.5 K). Furthermore, antiferromagnetic ordering is present at these temperatures. It is caused by a ferromagnetic coupling of the magnetic moments at Co²⁺ (3.60(5) μ_B at 1.5 K, 3.22(5) μ_B at 20 K) along the octahedra chains [CoCl_4/2(NH₃)₂] and antiferromagnetic coupling between neighbouring chains. According to heat capacity measurements the phase transition antiferromagnetic‐paramagnetic takes place at T_N = 26 K.     

Syntheses,and Crystal Structures of Indium Complexes with η2‐Piperidinyldithiocarbamate and η2‐Pyridine‐2‐Thionate Containing Ligands: Structures of [In(η2‐S2CNC5H10)3] and [In(η2‐pyS)3]

The η²‐thio‐indium complexes [In(η²‐thio)₃] (thio = S₂CNC₅H₁₀, 2 ; SNC₄H₄, (pyridine‐2‐thionate, pyS, 3 ) and [In(η²‐pyS)₂(η²‐acac)], 4 , (acac: acetylacetonate) are prepared by reacting the tris(η²‐acac)indium complex [In(η²‐acac)₃], 1 with HS₂CNC₅H₁₀, pySH, and pySH with ratios of 1:3, 1:3, and 1:2 in dichloromethane at room temperature, respectively. All of these complexes are identified by spectroscopic methods and complexes 2 and 3 are determined by single‐crystal X‐ray diffraction. Crystal data for 2 : space group, C2/c with a = 13.5489(8) Å, b = 12.1821(7) Å, c = 16.0893(10) Å, β = 101.654(1)°, V = 2600.9(3) ų, and Z = 4. The structure was refined to R = 0.033 and Rw = 0.086; Crystal data for 3 : space group, P2₁ with a = 8.8064 (6) Å, b = 11.7047 (8) Å, c = 9.4046 (7) Å, β = 114.78 (1)°, V = 880.13(11) ų, and Z = 2. The structure was refined to R = 0.030 and Rw = 0.061. The geometry around the metal atom of the two complexes is a trigonal prismatic coordination. The piperidinyldithiocarbamate and pyridine‐2‐thionate ligands, respectively, coordinate to the indium metal center through the two sulfur atoms and one sulfur and one nitrogen atoms, respectively. The short C‐N bond length in the range of 1.322(4)–1.381(6) Å in 2 and C‐S bond length in the range of 1.715(2)–1.753(6) Å in 2 and 3 , respectively, indicate considerable partial double bond character.     

Crystal structure and magnetic properties of tetra(monomethylammonium)hexachloroytterbatochloride(CH3NH3)4YbCl7

(CH₃NH₃)₄YbCl₇ has been synthesized from a solution of CH₃NH₃Cl and YbCl₃ in a mixture of ethnole/acetonitrile. The structure was solved from 1464 single crystal data by Patterson methods and refined to a final R_w = 0.035 space group P2, a = 9.972(6) Å, b = 7.605(5) Å, c = 12.866(6) Å, β = 90.53(4)°. The structure consists of alternating [YbCl₆]^3? octahedra and of tetrahedrally arranged [(CH₃NH₃)₄Cl]³⁺ units. Raman spectra display a splitting of frequencies related to the CH₃NH₃⁺ group in agreement with the structure determination. The magnetic susceptibility shows a remarkable deviation from a Curie-Weiss law below 170 K which may be explained by crystal field effects of Yb³⁺.     

Crystal Structures of {[Cd(phen)](C6H8O4)3/3} and {[Cd(phen)](C7H10O4)3/3} · 2H2O with C6H10O4 = Adipic Acid and C7H12O4 = Pimelic Acid

Two coordination polymers {[Cd(phen)](C₆H₈O₄)_3/3} ( 1 ) and {[Cd(phen)](C₇H₁₀O₄)_3/3} · 2H₂O ( 2 ) were structurally characterized by single crystal X‐ray diffraction methods. In 1 (C2/c (no. 15), a = 16.169(2)Å, b = 15.485(2)Å, c = 14.044(2)Å, β = 112.701(8)°, U = 3243.9(7)ų, Z = 8), the Cd atoms are coordinated by two N atoms of one phen ligand and five O atoms of three adipato ligands to form mono‐capped trigonal prisms with d(Cd‐O) = 2.271‐2.583Å and d(Cd‐N) = 2.309, 2.390Å. The [Cd(phen)] moieties are bridged by adipato ligands to generate {[Cd(phen)](C₆H₈O₄)_3/3} chains, which, via interchain π—π stacking interactions, are assembled into layers. Complex 2 (P1¯(no. 2), a = 9.986(1)Å, b = 10.230(3)Å, c = 11.243(1)Å, α = 66.06(1)°, β = 87.20(1)°, γ = 66.71(1)°, U = 955.7(2)ų, Z = 2) consists of {[Cd(phen)](C₇H₁₀O₄)_3/3} chains and hydrogen bonded H₂O molecules. The Cd atoms are pentagonal bipyramidally coordinated by two N atoms of one phen ligand and five O atoms of three pimelato ligands with d(Cd‐O) = 2.213—2.721Å and d(Cd‐N) = 2.329, 2.372Å. Through interchain π—π stacking interactions, the {[Cd(phen)](C₇H₁₀O₄)_3/3} chains resulting from [Cd(phen)] moieties bridged by pimelato ligands are assembled in to layers, between which the hydrogen bonded H₂O molecules are sandwiched.     

Synthesis and Structure of the Centered Cluster Compound Ba3(Zr6Cl18Be)

Reaction of powdered Zr with ZrCl₄, BaCl₂ and Be in suitable proportions in a Ta container at 800°C produces the title compound. Suitable monocrystals for X-ray diffraction were obtained from reactions to which a comparable amount of Hg₂Cl₂ had been added. The structure of Ba₃Zr₆Cl₁₈Be is a superstructure of the K₂ZrCl₆ · Zr₆Cl₁₈H type (R3 c, Z = 6; a = 9.6852 (9) Å, c = 52.52 (1) Å; R, R_w = 2.7, 3.2% for 826 independent reflections, 2θ ≤ 50°). Trigonally compressed [Zr₆(Be)Cl₁₂ⁱ]Cl₆^a clusters are interconnected by six-coordinate barium atoms that lie in Cl^a antiprisms (a twisted version of the Zr^IV site) while (9 + 3)-coordinate barium substitutes for potassium within chlorine layers. Distortions associated with the size and field of barium are responsible for the superstructure and for differences from other analogues.     

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 Lithiummesitolat [{LiOC6H2-2,4,6-(CH3)3}4(THF)3]

X-Ray Structure of [{LiOC₆H₂-2,4,6-(CH₃)₃}₄(THF)₃] The title compound crystallized from a THF/OEt₂ solution. Its crystal structure (monoclinic, P2₁/c, a = 21.362(3), b = 13.441(2), c = 17.188(2) Å, β = 98.39(1)°, Z = 4, R = 0,0911, wR² = 0,2562) is built up by cuban-like tetrameric units. Three of the four Li cations attain a coordination number of four by binding to an additional THF molecule. Li(4) without THF coordination has a short distance to one ortho-methyl group (Li(4)…C(27) 2.669(10) Å). The Li–O_ph bonding distances vary from 1.869(10) to 2.051(10) Å (average 1.97 Å); the average bonding distance for Li–O_THF is 2.012(10) Å. Averaged bonding angles for Li–O_ph–Li′ and O_ph–Li–O′_ph amount to 84.4(4)° and 95.4(4)°, respectively. The Li…Li distances significantly differ from each other. They range from 2.556(12) to 2.739(11) Å (average 2.65(1) Å).     

The Crystal Structure of MnF3 Revisited

We correct the crystal structure of MnF₃, of which the space group was reported as monoclinic C2/c (no. 15) with a = 8.9202, b = 5.0472, c = 13.4748 Å, β = 92.64°, V = 606.02 ų, Z = 12, mS48, T not given, likely 298 K. In the structure model proposed here, we use a unit cell of one third of the former volume. The ruby red crystals of MnF₃ were synthesized by a high-pressure/high-temperature method, where MnF₄ was used as a starting material. As determined on a single crystal, MnF₃ crystallizes in the monoclinic space group I2/a (no. 15) with a = 5.4964(11), b = 5.0084(10), c = 7.2411(14) Å, β = 93.00(3)°, V = 199.06(7) ų, Z = 4, mS16, T = 183(2) K. The crystal structure of MnF₃ is related by a direct group-subgroup transition to the VF₃ structure-type. We performed quantum chemical calculations on the crystal structure to allow the assignment of bands of the obtained vibrational spectra.     

Notiz zum Magnetischen Verhalten von Li3CrO4

Notice on the Magnetic Behaviour of Li₃CrO₄ Li₃CrO₄, a smaragd green powder, is due to powder photographs (Guinier-Simon-technique) isotypic with orthorhombic HT? Li₃PO₄, a = 6.30₉, b = 10.85₁, c = 4.95₂ Å, Z = 4. Between 298 and 10K the Curie-Weiss-Law is obeyed with μ=1.60 B.M. and Θ=+10 K. Below 5 K ferromagnetism is observed. ESR measurements at 4.2 K and more pronounced at 1.8 K show anisotropy of the ligand field.     

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).