Crystal structures and magnetic properties of BaTiF5 and CaTiF5

Single crystals of BaTiF₅ and CaTiF₅ were obtained by the Czochralski and Bridgman techniques, respectively. The crystal structures were determined by X-ray diffraction; BaTiF₅: $\text{14}\text{m}\text{, a = 15.091(5)}$Å, c = 7.670(3)Å; CaTiF₅: $\text{I2}\text{c}\text{, a = 9.080(4)}$Å, b = 6.614Å, c = 7.696(3)Å, β = 115.16(3)°. Both structures are characterized by the presence of either branched or straight chains of TiF₆ octahedra. BaTiF₅ contains the unusual dimeric unit (Ti₂F₁₀)^4?. Magnetic susceptibility measurements were performed on both compounds in the temperature range 4.2 to 300 K, however, no evidence for magnetic interactions between the Ti³⁺ moments were observed.     

Neue Fluropalladate(II)

New Fluoropalladates(II) Single crystal investigations on \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{*{20}c} {[6][4]} \\ {{\rm CsPdPdF}_{\rm 5} } \\ \end{array} $\end{document} (orange brown) demonstrate the close structural relationship to the CsAgFeF₆ – and CsNiNiF₆-type, respectively. One half of the Pd²⁺ ions is surrounded octahedrally, whereas the other half, because of the “absence” of one F^?, is coordinated planar quadratically. CsPd₂F₅ crystallizes orthorhombic (Imma – D, No. 74; Z = 4) with a = 6.53₃, b = 7.86₂, c = 10.79 Å (four circle diffractometer data). From Guinier data are isotypic CsMgPdF₅ (yellow, a = 6.603(2), b = 7.415(2), c = 10.548(3) Å), CsZnPdF₅ (beige, a = 6.576(1), b = 7,483(2), c = 10.645(2) Å), CsNiPdF₅ (yellow, a = 6.499(1), b = 7.504(2), c = 10.575(3) Å) and CsCoPdF₅ (brown, a = 6.527(1), b = 7.553(1), c = 10.659(2) Å). Besides of CsPd₂F₅ there exist compounds of the composition Me₃PdF₅ on the alkali-rich side of the system MeF/PdF₂. Single crystal investigations for Rb₃PdF₃ (yellow, P4/mbm–D, No. 127; Z = 2) led to a = 7.46₇, c = 6.49₇ Å (four circle diffractometer data). Isotypic are (single crystal data) Cs₃PdF₅ (yellow, a = 7.84₈, c = 6.68₈ Å) and Rb₂CsPdF₅ (yellow, ordered distribution of the alkali ions, a = 7.57₅, c = 6.44₅ Å).     

A Novel 3D Framework Coordination Polymer based on Succinato bridged Helical Chains Connected by 4, 4' ‐ Bipyridine: [Cu(bpy)(H2O)2(C4H4O4)]?2H2O

Blue needle—shaped crystals of [Cu(bpy)(H₂O)₂(C₄H₄O₄)]· 2H₂O were obtained by slow evaporation of a methanolic aqueous solution containing a fresh Cu(C₄H₄O₄)· 2H₂O precipitate, 4, 4′—bipyridine, and ammonia. Within the complex, the six—coordinated Cu atoms are linked by bis—monodentate gauche succinate anions into chains propagating helically around the [001] axis. The chains are interconnected by 4, 4′—bipyridine ligands into a 3D framework with the crystal H₂O molecules located in the channels along the [100], [010] and [110] directions. The Cu²⁺ ions are in distorted octahedral coordination of two nitrogen and four oxygen atoms (equatorial bonds: Cu—N 1.986(5), 2.015(5)Å; Cu—O 1.950(6), 1.954(6)Å; axial bonds Cu—O: 2.524(9), 2.539(8)Å). Furthermore, the thermal and magnetic behavior of the compound will be discussed. Crystal data: hexagonal, P6₁ (no. 169), a = 11.066(2)Å, c = 24.965(5)Å, V = 2647.5(8)ų, Z = 6, R = 0.0528 and wR₂ = 0.1103 for 1426 observed reflections (F_o² > 2σ(F_o²)) out of 2170 unique reflections.     

Molecular and crystal structure of 1-amino-3,5-diphenyl-2,4,4,6,6-Pentacyano-cyclohex-1-ene and 1-amino-3,5-diphenyl-2,4,4,6-tetracyanocyclohex-1-ene

Molecular and crystal structures of 1-amino-3,5-diphenyl-2,4,4,6,6-pentacyano-cyclohex-1-ene (I) and 1-amino-3,5-diphenyl-2,4,4,6-tetracyanocyclohex-1-ene (II) are studied to examine intermolecular interactions. Crystal data for (I): space group P2₁, a=11.172(3), b=6.561(2), c=16.390(4) Å, β=100.25(2)⁰, V=1182.1 ų, Z=2, R=0.046; for (II): space group P1, a=10.756(3), b=10.890(3), c=12.999(3) Å, α=62.20(2), β=70.73(2), γ=65.42(2)⁰, V=1207.2 ų, Z=2, R=0.074. Intermolecular bonds via the aminonitrile fragment in (I) lead to formation of chains along they axis: N1…N6′ (1?x, ?1/2+y, 1?z) of 3.465(8) Å, N6…N1″ (1?x, 1/2+y, 1?z), and the contact with the solvent (acetone) O1…N1 of 2.984(7) Å. In compound (II), the intermolecular contacts N1…N5′ (?x+1, ?y, ?z+1) of 3.064(7) Å link the molecules into dimeric associates.     

Structural aspects of the metal-insulator transitions in V0.985Al0.015O2

The crystal structure of V_0.985Al_0.015O₂ has been refined from single-crystal X-ray data at four temperatures. At 373°K it has the tetragonal rutile structure. At 323°K, which is below the first metal-insulator transition, it has the monoclinic M₂ structure, where half of the vanadium atoms are paired with alternating short (2.540 Å) and long (3.261 Å) V-V separations. The other half of the vanadium atoms form equally spaced (2.935 Å) zigzag V chains. At 298°K, which is below the second electric and magnetic transition, V_0.985Al_0.015O₂ has the triclinic T structure where both vanadium chains contain V-V bonds, V(1)-V(1) = 2.547 Å and V(2)-V(2) = 2.819 Å. At 173°K the pairing of the V(1) chain remains constant: V(1)-V(1) = 2.545 Å, whereas that of the V(2) chain decreases: V(2)-V(2) = 2.747 Å. From the variation of the lattice parameters as a function of temperature it seems that these two short V-V distances will not become equal at lower temperatures. The effective charges as calculated from the bond strengths at 298 and 173°K show that a cation disproportionation has taken place between these two temperatures. About 20% of the V⁴⁺ cations of the V(1) chains have become V³⁺ and correspondingly 20% of the V⁴⁺ cations of the V(2) chains have become V⁵⁺. This disproportionation process would explain the difference between the two short V-V distances. Also it would explain why the T → M₁ transition does not take at lower temperatures.     

Darstellung und Struktur der Komplexverbindungen trans‐[CoIII(py)4F2][H2F3] und [Pd(py)4]F2 · 1,5 HF · 2 H2O

Synthesis and Crystal Structures of the Complexes trans ‐[Co^III(py)₄F₂][H₂F₃] and [Pd(py)₄]F₂ · 1.5 HF · 2 H₂O The cobalt complex trans‐[Co(III)(py)₄F₂][H₂F₃] ( 1 ) has been prepared by electrochemical oxidation of CoF₂ in a pyridine/HF mixture and the palladium complex [Pd(py)₄]F₂ · 1.5 HF · 2 H₂O ( 2 ) has been obtained via halogen exchange between Pd(py)₂Cl₂ and AgF₂ in pyridine. 1 and 2 crystallize in the space group C2/c with a = 27.928(14), b = 9.019(3), c = 18.335(8) Å, β = 113.41(3)° for 1 and a = 28.183(9), b = 9.399(3), c = 17.397(6) Å, β = 104.66(3)° for 2 , respectively. Concerning the shape and location of the M(py)₄ fragments 1 and 2 are isostructural. The metal atoms occupy special positions in their unit cells with the result that four complex atoms have C₂ symmetry and four complex cations have C_i symmetry giving a total of Z = 8. In 1 two F^– ions complete an octahedral coordination around the Co atoms (Co–F 1.820(2) to 1.834(3) Å). In 2 the shortest Pd–F distance is 3.031(2) Å. This precludes the existence of Pd–F bonds. In 1 one can identify H₂F₃^– groups. In 2 there are larger aggregates, consisting of F^–, HF, and H₂O subunits, connected by H‐bridges. In spite of these differences, both complexes belong to the same type of structure, which may be of a common type M^x+(py)₄F_x · y HF · z H₂O.     

Synthesis and characterization of the new 22-π aromatic furan-containing macrocycle, “ozaphyrin”

The new 22-π, aromatic “pentaplanar” macrocycle, ozaphyrin ( 6 ), has been synthesized by a McMurry coupling of 5,5′-diformyl-4,4′-dipropyl-2,2′-bipyrrole ( 1 ) with 2,5-bis(5-formyl-4-propyl-2-pyrrolyl)furan ( 5 ). This synthetic pathway to ozaphyrin and its characterization by ¹H nmr spectroscopy, uv-visible spectroscopy, cyclic voltammetry, and X-ray crystallography are described. The structure consists of layers of planar, staggered macrocycles stacked perpendicular to the α-axis. Ozaphyrin crystallizes with four formula units in the monoclinic space group C⁵_2h-P2₁/n in a cell of dimensions a = 10.481(7) Å, b = 17.353(17) Å, c = 18.726(12) Å, and β = 102.84(5)° (108 K). The structure has been refined on F² (5171 unique reflections, 411 variables) to R_w(F_o²) = 0.165. The conventional agreement index R(F) is 0.074 for the 3289 reflections have F_o²>2o(F_o²).     

The crystal structure of a complex cerium(III) molybdate; Ce6(MoO4)8(Mo2O7)

Ce₆Mo₁₀O₃₉ crystallizes in the triclinic system with unit-cell dimensions (from single-crystal data) a = 10.148(5), Å, b = 18.764(6), Å, c = 9.566(5), Å, α = 103.12(7)°, β = 78.07(7)°, γ = 107.69(7)°, and space group $\text{P}\text{1}\text{, z = 2}$. The structure was solved using direct methods with 3113 countermeasured reflections (MoKα radiation), and refined using Fourier and least-squares techniques to a conventional R of 0.039 (ωR = 0.047). Ce₆Mo₁₀O₃₉ has a structure that consists of isolated MoO₄ tetrahedra together with one corner-shared pair of tetrahedra, linked to irregular eight-coordinate Ce(III) polyhedra. The average MoO distance of 1.77 Å, and average CeO distance of 2.52 Å are in good agreement with previously reported values.     

Pentanuclear heterobimetallic 3d-4f complexes of Ln<Subscript>2</Subscript>M<Subscript>3</Subscript>-type — structure and magnetism

From a series of pentanuclear, heterobimetallic complexes of the general composition [{Ln(H₂O)_n}₂{Ni(dto)₂}₃] · xH₂O, four complexes (Ln = Gd(III) with n = 4; Ln = Dy(III), Ho(III), or Er(III), with n = 5; x = 9–12; dto = 1,2-dithiooxalate) were studied due to their large magnetic moments (up to 14.65 B.M.). The magnetic properties of these complete series were measured at room temperature and the temperature dependent magnetic properties of the complexes Gd₂Ni₃, Dy₂Ni₃, Ho₂Ni₃, and Er₂Ni₃ were studied at room temperature down to 1.8 K. Whereas the intramolecular metal-metal distances were rather long (Ni1-Ni2: 11.0–11.5 Å; Ln-Ni: 6.0–6.3 Å), relatively short intermolecular metal-metal distances (Ni1-Ni2′: 3.5 Å; Er-Er′: 6.0 Å) were found in the crystal lattice, giving rise to weak intermolecular metal-metal interactions. These weak spin interactions were also supported by the EPR spectrum of a powdered sample of the diamagnetically undiluted Gd₂Ni₃ complex.     

One‐dimensionally linked Chain Crown Ether Complexes. Syntheses and Crystal Structures of Complexes [K(18‐Crown‐6)]2[M(SeCN)4](H2O) (M = Pd,Pt)

18‐crown‐6(18‐C‐6) complexes with K₂[M(SeCN)₄] (M = Pd, Pt): [K(18‐C‐6)]₂[Pd(SeCN)₄] (H₂O) ( 1 ) and [K(18‐C‐6)]₂[Pt(SeCN)₄](H₂O) ( 2 ) have been isolated and characterized by elemental analysis, IR spectroscopy and single crystal X‐ray analysis. The complexes crystallize in the monoclinic space group P2₁/n with cell dimensions: 1 : a = 1.1159(3) Å, b = 1.2397(3) Å, c = 1.6003(4) Å, β = 92.798(4)°, V = 2.2111(8) ų, Z = 2, F(000) = 1140, R₁ = 0.0418, wR₂ = 0.0932 and 2 : a = 1.1167(3) Å, b = 1.2394(3) Å, c = 1.5968(4) Å, β = 92.945(4)°, V = 2.2071(9) ų, Z = 2, F(000) = 1204, R₁ = 0.0341, wR₂ = 0.0745. Both complexes form one‐dimensionally linked chains of [K(18‐C‐6)]⁺ cations and [M(SeCN)₄]^2— (M = Pd, Pt) anions bridged by K‐O‐K interactions between adjacent [K(18‐C‐6)]⁺ units.     

Crystal and molecular structure of cis- and trans-2,4-dihydroxy-2,4-dimethylcyclohexanetrans-1-acetic acid γ-lactone

During the transformation process of limonene to tetrahydrofuran derivatives, the title compounds (±)-( 4 ) have been obtained as crystalline products and subjected to X-ray analysis. The crystals of trans-( 4 ) are orthorhombic, space group P2₁2₁2₁, with the lattice constants a = 7.0445(5) Å, b = 10.0908(4) Å, c = 14.0309(6) Å; the absolute configuration at atoms C1, C2, and C4 is R_c1, S_c2, and R_c4, respectively. The isomeric form cis-( 4 ) crystallizes in the monoclinic system, space group P2₁, with the following unit-cell parameters: a = 10.8275(4) Å, b = 8.6994(5) Å, c = 16.4722(6) Å, β = 106.515(3)°. The asymmetric part of the unit cell of cis-( 4 ) contains three independent molecules. Each of these three molecules has the identical absolute configuration at all centers of chirality: S_c1, S_c2, and R_c4. © John Wiley & Sons, Inc.     

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.     

Zur Kenntnis der Fluoride zweiwertiger Lanthanoide. III. Neue Fluoroperowskite vom Typ CsLn1−xLn′xF3 und RbLn1−xLn′xF3 mit Ln = Eu2+ bzw. Sm2+ und Ln′ = Yb2+

On Fluorides of Divalent Lanthanoids. III. New Fluoroperovskites of the MLn_1?xLn′_xF₃ Type with M = Cs, Rb; Ln = Eu²⁺, Sm²⁺; Ln′ Yb²⁺ New fluoroperovskites with divalent lanthanoids have been prepared. They are: CsEu_1?xYb_xF₃, yellow, with x = 0.25, a = 4.737(1) Å; x = 0.50, a = 4.696(1) Å; x = 0.75, a = 4.653(1) Å; CsSm_xYb_1?xF₃, violet, with x = 0.25, a = 4.656(1) Å; x = 0.18, a = 4.645(1) Å, the latter mixed with Sm_0.68Yb_0.32F₃, a = 5.781(1) Å; RbEu_xYb_1?xF₃, orange, with x = 0.25, a = 4.573(1) Å; x = 0.23, a = 4.568(1) Å, the latter mixed with Eu_0.94Yb_0.06F₂, a = 5.827(1) Å; RbSm_0.13Yb_0.87F₃, brown, a = 4.555(1) Å.     

Crystal structure refinement for trans-[Pd(NO3)2(H2O)2]

Single crystals of trans-[Pd(NO₃)₂(H₂O)₂] were obtained, and the crystal structure of this complex, previously obtained for polycrystals, was refined. Crystal data (BRUKER X8APEX diffractometer): a = 4.9973(7) Å, b = 10.5982(14) Å, c = 11.7008(17) Å, V = 619.70(15) ų, space group Pbca, Z = 4, d _calc = 2.856 g/cm³. The structure is composed of neutral complexes with a trans configuration. The square plane environment of the Pd atom is formed by four oxygen atoms (Pd-O(NO₃) 1.999(5) Å, Pd-O(H₂O) 2.030(5) Å) and completed to a distorted bipyramid by two intramolecular contacts (Pd…O(NO₃) 2.926 Å). The shortest hydrogen bonds are O…H 2.72 Å.     

Struktur und magnetische Eigenschaften von Bis{3‐amino‐1,2,4‐triazolium(1+)}pentafluoromanganat(III): (3‐atriazH)2[MnF5]

Structure and Magnetic Properties of Bis{3‐amino‐1,2,4‐triazolium(1+)}pentafluoromanganate(III): (3‐atriazH)₂[MnF₅] The crystal structure of (3‐atriazH)₂[MnF₅], space group P1, Z = 4, a = 8.007(1) Å, b = 11.390(1) Å, c = 12.788(1) Å, α = 85.19(1)°, β = 71.81(1)°, γ = 73.87(1)°, R = 0.034, is built by octahedral trans‐chain anions [MnF₅]^2–_∞ separated by the mono‐protonated organic amine cations. The [MnF₆] octahedra are strongly elongated along the chain axis (<Mn–F_ax> 2.135 Å, <Mn–F_eq> 1.842 Å), mainly due to the Jahn‐Teller effect, the chains are kinked with an average bridge angle Mn–F–Mn = 139.3°. Below 66 K the compound shows 1D‐antiferromagnetism with an exchange energy of J/k = –10.8 K. 3D ordering is observed at T_N = 9.0 K. In spite of the large inter‐chain separation of 8.2 Å a remarkable inter‐chain interaction with |J′/J| = 1.3 · 10^–5 is observed, mediated probably by H‐bonds. That as well as the less favourable D/J ratio of 0.25 excludes the existence of a Haldene phase possible for Mn³⁺ (S = 2).     

Polychalcogenoaurates(I) with pseudo-onedimensional structures: Preparation and crystal structure of Cs2Au2Se3

Cs₂Au₂Se₃ was obtained as red platelike crystals by reacting a stoichiometric mixture of Cs₂Se, Au and Se at 670K. It crystallizes in space group C2/c, Z = 4 with a = 9.769(5) Å, b = 13.44(1) Å, c = 7.178(3) Å, β = 90.69(1)°. The crystal structure was determined from single crystal data and refined to a conventional R of 0.042 for 674 Fo's and 34 variables. The characteristic structural feature of this new selenoaurate is the formation of infinite helical anionic chains, _∞¹-[AuSeAuSe₂]²⁻ which run parallel to [001] and are separated by the alkali cations. The average Au-Se bond length is 2.402 Å, the bond length in the Se₂-unit is 2.436 Å. Au…Au contacts of 3.200 Å, are formed within the anionic chains. The cesium atoms are coordinated to seven Se in an irregular configuration.     

The effect of oxygen vacancy on the magnetic properties in the system SrCoO3−δ (0 < δ < 0.5)

The cubic perovskite SrCoO_3?δ (0.05 ? δ ? 0.26) was prepared under high oxygen pressures of 50–2600 bars, and its crystallographic and magnetic properties were examined. From the results, it was found that oxygen deficiency strongly influences the unit-cell parameters and the Curie temperatures. The unit-cell parameter a₀ = 3.836 Å and the Curie temperature 222°K for SrCoO₃ were determined.     

Complex Topology of Uranyl Polyphosphate Frameworks: Crystal Structures of α‐, β‐K[(UO2)(P3O9)] and K[(UO2)2(P3O10)]

Three new uranyl polyphosphates, α‐K[(UO₂)(P₃O₉)] ( 1 ), β‐K[(UO₂)(P₃O₉)] ( 2 ), and K[(UO₂)₂(P₃O₁₀)] ( 3 ), were prepared by high‐temperature solid‐state reactions. The crystal structures of the compounds have been solved by direct methods: 1 – monoclinic, P2₁/m, a = 8.497(1), b = 15.1150(1), c = 14.7890(1) Å, β = 91.911(5)°, V = 1898.3(3) ų, Z = 4, R₁ = 0.0734 for 4181 unique reflections with |F₀| ≥ 4σ_F; 2 – monoclinic, P2₁/n, a = 8.607(1), b = 14.842(2), c = 14.951(1) Å, β = 95.829(5)°, V = 1900.0(4) ų, Z = 4, R₁ = 0.0787 for 3185 unique reflections with |F₀| ≥ 4σ_F; 3 – Pbcn, a = 10.632(1), b = 10.325(1), c = 11.209(1) Å, V = 1230.5(2) ų, Z = 4, R₁ = 0.0364 for 1338 unique reflections with |F₀| ≥ 4σ_F. In the structures of 1 and 2 , phosphate tetrahedra share corners to form infinite [PO₃]^? chains, whereas, in the structure of 3 , tetrahedra form linear [P₃O₁₀]^5? trimers. The structures are based upon 3‐D frameworks of U and P polyhedra linked by sharing common O corners. The infinite [PO₃]^? chains in the structures of 1 and 2 are parallel to [100] and [–101], respectively. The uranyl polyphosphate frameworks are occupied by host K⁺ cations.     

Crystal Structure of the Coordinatively Unsaturated 2-Pyridylphosphine Pd(0) Complex Pd(PPh2Py)3

The three-coordinate tris(2-pyridylphosphine)palladium(0) complex is the first example of a group 10 metal complex bearing pyridine substituted phosphine ligand, whose crystal structure is determined. Pd(PPh₂py)₃ crystallizes in the triclinic space group $ {\rm P}\bar 1 $, with a = 12.874(4) Å, b = 14.162(3) Å, c = 14.912(3) Å, α = 87.76(2)°, β = 66.50(2)°, γ = 63.17(2)°, Z = 2, and V = 2191(1) ų. Full-matrix least-squares refinement of 523 variables using 4911 data (F²_o > 3σF²_o) gave R = 0.033 and R_w = 0.033. The pyridine ring is disordered. Possible weak interactions among Ph rings or Py rings and Pd center are discussed. Close approach of the ortho hydrogen on phenyl rings to the Pd center may imply facile ortho metallation.     

K2Br(OH) und Rb2Br(OH): Zwei neue ternäre Alkalimetallhalogenidhydroxide mit ausgeprägter Strukturverwandtschaft zu KOH bzw. RbOH

K₂Br(OH) and Rb₂Br(OH): Two New Ternary Alkali Metal Halide Hydroxides with a Pronounced Structural Relationship to KOH resp. RbOH Two isotypic compounds K₂Br(OH) and Rb₂Br(OH) were prepared in the systems KOH/KBr and RbOH/RbBr. Their structures were determined by single crystal X-ray methods: K₂Br(OH): P2₁/m, Z = 2, a = 6.724(1) Å, b = 4.272(4) Å, c = 8.442(2) Å, β = 108.14(2)°, Z(F_o) = 651 with (F_o)² ≥ 3σ(F_o)², Z(parameter) = 28, R/R_w = 0.041/0.047 Rb₂Br(OH): P2₁/m, Z = 2, a = 6.918(3) Å, b = 4.483(2) Å, c = 8.850(5) Å, β = 108.08(6)°, Z(F_o) = 326 mit (F_o)² ≥ 3σ(F_o)², Z(parameter) = 27, R/R_w = 0.074/0.082. The compounds are built up by chains of [M₂(OH)⁺] connected via Br^?. The structure of the chains as well as their orientation to one another show a pronounced relationship to the structures of the room temperature modifications of the isotypic binary hydroxides KOH and RbOH.