Synthesis,Structure and Thermodynamic Property of a New Lithium Borate: Li4[B8O13(OH)2]·3H2O

A new hydrated lithium borate, Li₄[B₈O₁₃(OH)₂]·3H₂O, has been hydrothermally synthesized and characterized by single crystal X‐ray diffraction, FT‐IR spectroscopy, simultaneous TGA‐DTA and chemical analysis. It crystallizes in the triclinic, space group , a=8.4578(5) Å, b=8.7877(5) Å, c=10.8058(7) Å, α=87.740(3)°, β=71.819(3)°, γ=61.569(3)°, Z=2, V=665.26(7) ų, D_c=2.043 g/cm³. Its crystal structure features polyborate anionic layers with the larger odd 13‐membered boron rings constructed by [B₈O₁₃(OH)₂]^4? FBBs. Through designing the thermochemical cycle, the standard molar enthalpy of formation of this borate was determined to be ?(7953.8±6.6) kJ·mol^?1 by using a heat conduction microcalorimeter.     

Structural Patterns and Dimensionality in Magnesium Borophosphates: The Crystal Structures of Mg2(H2O)[BP3O9(OH)4] and Mg(H2O)2[B2P2O8(OH)2]·H2O

Hydrothermal investigations in the system MgO/B₂O₃/P₂O₅(/H₂O) yielded two new magnesium borophosphates, Mg₂(H₂O)[BP₃O₉(OH)₄] and Mg(H₂O)₂[B₂P₂O₈(OH)₂]·H₂O. The crystal structures were solved by means of single crystal X‐ray diffraction. While the acentric crystal structure of Mg₂(H₂O)[BP₃O₉(OH)₄] (orthorhombic, P2₁2₁2₁ (No. 19), a = 709.44(5) pm, b = 859.70(4) pm, c = 1635.1(1) pm, V = 997.3(3) × 10⁶ pm³, Z = 4) contains 1D infinite chains of magnesium coordination octahedra interconnected by a borophosphate tetramer, Mg(H₂O)₂[B₂P₂O₈(OH)₂]·H₂O (monoclinic, P2₁/c (No. 14), a = 776.04(5) pm, b = 1464.26(9) pm, c = 824.10(4) pm, β = 90.25(1)°, V = 936.44(9) × 10⁶ pm³,Z = 4) represents the first layered borophosphate with 6³ net topology. The structures are discussed and classified in terms of structural systematics.     

Das erste Vanadium(III)‐Borophosphat: Darstellung und Kristallstruktur von CsV3(H2O)2[B2P4O16(OH)4]

The First Vanadium(III) Borophosphate: Synthesis and Crystal Structure of CsV₃(H₂O)₂[B₂P₄O₁₆(OH)₄] CsV₃(H₂O)₂[B₂P₄O₁₆(OH)₄] was prepared under mild hydrothermal conditions (T = 165 °C) from mixtures of CsOH_(aq), VCl₃, H₃BO₃, and H₃PO₄ (molar ratio 1 : 1 : 1 : 2). The crystal structure was determined by X‐ray single crystal methods (monoclinic; space group C2/m, No. 12): a = 958.82(15) pm, b = 1840.8(4) pm, c = 503.49(3) pm; β = 110.675(4)°; Z = 2. The anionic partial structure contains oligomeric units [BP₂O₈(OH)₂]^5–, which are built up by a central BO₂(OH)₂ tetrahedron and two PO₄ tetrahedra sharing common corners. V^III is octahedrally coordinated by oxygen of adjacent phosphate tetrahedra and OH groups of borate tetrahedra as well as oxygen of phosphate tetrahedra and H₂O molecules, respectively (coordination octahedra VO₄(OH)₂ and VO₄(H₂O)₂). The oxidation state +3 for vanadium was confirmed by measurements of the magnetic susceptibility. The trimeric borophosphate groups are connected via vanadium centres to form layers with octahedra‐tetrahedra ring systems, which are likewise linked via V^III‐coordination octahedra. Overall, a three‐dimensional framework constructed from VO₄(OH)₂ and VO₄(H₂O)₂ octahedra as well as BO₂(OH)₂ and PO₄ tetrahedra results. The structure contains channels running along [001], which are occupied by Cs⁺ in a distorted octahedral coordination (CsO₄(H₂O)₂).     

Isotype Borophosphate MII(C2H10N2)[B2P3O12(OH)] (MII = Mg,Mn, Fe,Ni, Cu,Zn): Verbindungen mit Tetraeder‐Schichtverbänden

Isotypic Borophosphates M^II(C₂H₁₀N₂)[B₂P₃O₁₂(OH)] (M^II = Mg, Mn, Fe, Ni, Cu, Zn): Compounds containing Tetrahedral Layers The isotypic compounds M^II(C₂H₁₀N₂) · [B₂P₃O₁₂(OH)] (M^II = Mg, Mn, Fe, Ni, Cu, Zn) were prepared under hydrothermal conditions (T = 170 °C) from mixtures of the metal chloride (chloride hydrate, resp.), Ethylenediamine, H₃BO₃ and H₃PO₄. The orthorhombic crystal structures (Pbca, No. 61, Z = 8) were determined by X‐ray single crystal methods (Mg(C₂H₁₀N₂)[B₂P₃O₁₂(OH)]: a = 936.81(2) pm, b = 1221.86(3) pm, c = 2089.28(5) pm) and Rietveld‐methods (M^II = Mn: a = 931.91(4) pm, b = 1234.26(4) pm, c = 2129.75(7) pm, Fe: a = 935.1(3) pm, b = 1224.8(3) pm, c = 2088.0(6) pm, Ni: a = 939.99(3) pm, b = 1221.29(3) pm, c = 2074.05(7) pm, Cu: a = 941.38(3) pm, b = 1198.02(3) pm, c = 2110.01(6) pm, Zn: a = 935.06(2) pm, b = 1221.33(2) pm, c = 2094.39(4) pm), respectively. The anionic part of the structure contains tetrahedral layers, consisting of three‐ and nine‐membered rings. The M^II‐ions are in a distorted octahedral or tetragonal‐bipyramidal [4 + 2] (copper) coordination formed by oxygen functions of the tetrahedral layers. The resulting three‐dimensional structure contains channels running along [010]. Protonated Ethylenediamine ions are fixed within the channels by hydrogen bonds.     

RbFe[BP2O8(OH)]: Ein neues Borophosphat mit offen-verzweigten Vierer-Einfach-Tetraederketten

RbFe[BP₂O₈(OH)]: A New Borophosphate Containing Open-Branched Tetrahedral Vierer-Einfach Chains RbFe[BP₂O₈(OH)] is formed under mild hydrothermal conditions (T = 165–170 °C) from a mixture of RbOH_(aq), FeCl₂ · 4 H₂O, H₃BO₃ and H₃PO₄. The crystal structure of the monoclinic compound was solved by x-ray single crystal methods (space group P2₁/c, No. 14): a = 935.8(5) pm, b = 833.9(6) pm, c = 965.6(5) pm; β = 101.69(4)°; Z = 4. The anionic partial structure contains open-branched vierer-einfach chains [BP₂O₈(OH)]^4–, which are formed by alternating borate and phosphate tetrahedra sharing common corners. Fe³⁺ is in an octahedral coordination (FeO₅(OH)), while Rb⁺ is irregularly coordinated by ten oxygen-functions of neighbouring tetrahedra.     

Synthesis,Crystal Structure of a New Structure Type,and Thermal Analysis of the Ammonium Borophosphate (NH4)2[B2P3O11(OH)]

(NH₄)₂[B₂P₃O₁₁(OH)] was synthesized as a crystalline colorless powder by reaction of (NH₄)₂HPO₄, H₃BO₃, and H₃PO₄ under hydrothermal conditions at 180 °C. According to X‐ray single‐crystal investigations (NH₄)₂[B₂P₃O₁₁(OH)] crystallizes in a new structure type in the orthorhombic space group P2₁2₁2₁ (no. 19) [Z = 4, a = 4.509(3), b = 14.490(11), c = 16.401(12) Å, R₁ = 0.046, wR₂ = 0.093, 1682 data, 200 parameters]. The crystal structure comprises infinite layers of corner‐sharing borate, phosphate and hydroxo‐phosphate tetrahedra with ammonium ions in‐between. The loop‐Branched (lB) zweier‐single layer reveals an open‐Branched (oB) vierer‐single ring as fundamental building unit (FBU), which was observed in (NH₄)₂Mn^II[B₂P₃O₁₁(OH)₂]Cl^[1] for the first time. Besides the spectroscopic properties the thermal behavior is presented as well.     

A new hydrated ammonium hydroxy­borate, (NH4)2[B10O14(OH)4]·H2O

The structure of a new synthetic compound, di­ammonium tetra­hydroxy­deca­borate monohydrate, has been determined by single‐crystal X‐ray diffraction. It crystallizes in triclinic space group and all atoms occupy general sites. The title compound is composed of [B₁₀O₁₅(OH)₄]⁴⁻ ions as the fundamental building blocks, and these are linked end‐to‐end by sharing two common O atoms, thus producing infinite chains of composition [B₁₀O₁₄(OH)₄]_n^2n–. These chains are linked by hydrogen bonds, thus forming borate sheets. Water mol­ecules and ammonium ions between these sheets connect adjacent sheets via hydrogen bonds.     

(Ni3–xMgx)[B3P3O12(OH)6] · 6 H2O (x ≈ 1.5): A Novel BorophosphateHydrate Containing Isolated Six‐Membered Rings of Tetrahedra

A novel borophosphate‐hydrate, (Ni_3–xMg_x)[B₃P₃O₁₂(OH)₆] · 6 H₂O (x ≈ 1.5), has been prepared by hydrothermal synthesis (T = 170 °C) from a mixture of NiCl₂ · 6 H₂O, Mg(OH)₂, B₂O₃ and H₃PO₄. The crystal structure was determined at 293 K from single‐crystal X‐ray diffraction data (trigonal, R3c (no. 167), a = 14.957(10) Å, c = 13.812(6) Å, V = 2676(2) ų, Z = 6, R₁ = 0.0276, wR₂ = 0.0714 for 779 observed reflections with I > 2σ(I)). The crystal structure contains unbranched six‐membered rings [B₃P₃O₁₂(OH)₆]^6– of alternating corner linked borate and phosphate tetrahedra, which are stacked along [001] and connected via M^IIO₂(OH)₂(H₂O)₂ coordination polyhedra. Hydrogen bonding between the tetrahedral six‐membered rings and M^IIO₂(OH)₂(H₂O)₂ octahedra leads to a further cross‐linking. With respect to the arrangement of isolated six‐membered tetrahedral rings the crystal structure of this borophosphate‐hydrate is closely related to the cyclo‐hexasilicate dioptase, Cu₆[Si₆O₁₈] · 6 H₂O.     

Zwei Dodekahydro‐closo‐Dodekaborate mit Lone‐Pair‐Kationen der 6. Periode im Vergleich: Tl2[B12H12] und Pb(H2O)3[B12H12]·3H2O

During the reaction of an aqueous solution of (H₃O)₂[B₁₂H₁₂] with Tl₂CO₃ anhydrous thallium(I) dodecahydro‐closo‐dodecaborate Tl₂[B₁₂H₁₂] is obtained as colorless, spherical single crystals. It crystallizes in the cubic system with the centrosymmetric space group Fm$\bar{3}$ (a = 1074.23(8) pm, Z = 4) in an anti‐CaF₂ type structure. Four quasi‐icosahedral [B₁₂H₁₂]^2– anions (d(B–B) = 180–181 pm, d(B–H) = 111 pm) exhibit coordinative influence on each Tl⁺ cation and provide a twelvefold coordination in the shape of a cuboctahedron (d(Tl–H) = 296 pm). There is no observable stereochemical activity of the non‐bonding electron pairs (6s² lone pairs) at the Tl⁺ cations. By neutralization of an aqueous solution of the acid (H₃O)₂[B₁₂H₁₂] with PbCO₃ and after isothermic evaporation colorless, plate‐like single crystals of lead(II) dodecahydro‐closo‐dodecaborate hexahydrate Pb(H₂O)₃[B₁₂H₁₂] · 3H₂O can be isolated. This compound crystallizes orthorhombically with the non‐centrosymmetric space group Pna2₁ (a = 1839.08(9), b = 1166.52(6), c = 717.27(4) pm, Z = 4). The crystal structure of Pb(H₂O)₃[B₁₂H₁₂] · 3H₂O is characterized as a layer‐like arrangement. The Pb²⁺ cations are coordinated in first sphere by only three oxygen atoms from water molecules (d(Pb–O) = 247–248 pm). But a coordinative influence of the [B₁₂H₁₂]^2– anions (d(B–B) = 173–181 pm, d(B–H) = 93–122 pm) on lead has to be stated, too, as three hydrogen atoms from three different hydroborate anions are attached to the Pb²⁺ cations (d(Pb–H) = 258–270 pm) completing their first‐sphere coordination number to six. These three oxygen and three hydrogen ligands are arranged as quite irregular polyhedron leaving enough space for a stereochemical lone‐pair activity (6sp) at each Pb²⁺ cation. Since additional intercalating water of hydration is present as well, both classical H–O^δ– ··· ^+δH–O‐ and unconventional B–H^δ– ··· ^+δH–O hydrogen bonds play a significant role in the stabilization of the entire crystal structure.     

Synthesis,Crystal Structure,and Characterization of a Novel Metallo‐Organically‐Templated Pentaborate with Mixed Ligands

A novel metallo‐organically templated pentaborate with layered framework, [Cd(TETA)(C₂H₃O₂)][B₅O₆(OH)₄] ( 1 ) (TETA = triethylenetramine), was synthesized under mild solvothermal conditions. The structure was determined by single‐crystal X‐ray diffraction and further characterized by FT‐IR spectroscopy, elemental analysis, thermogravimetric analysis, and photoluminescence spectroscopy. The structure consists of an isolated polyborate anion [B₅O₆(OH)₄]^– and the cadmium complex cation of [Cd(TETA)(C₂H₃O₂)]⁺, which contains both organic amine and organic acid ligands. The [B₅O₆(OH)₄]^– units are connected together by hydrogen bonds, and a 2D sheet‐like framework with rectangle‐like 12‐membered boron rings are formed. The [Cd(TETA)(C₂H₃O₂)]⁺ complex cations are located in the free space between the layers and connect the adjacent borate layers through hydrogen bonds to form a three‐dimensional supramolecular network. The luminescent properties of the compound were studied for the first time in the series of metallo‐organically‐templated pentaborates, and a blue luminescence occurs with an emission maximum at 468 nm upon excitation at 397 nm.     

Synthesis,Crystal Structure,Vibrational Spectroscopy and Thermal Behavior of the First Alkali Metal Hydrated Hexaborate： K2[B6O9（OH）2]

New hydrated potassium hexaborate K2[B6O9（OH）2] has been synthesized under mild solvothermal conditions. The structure was determined by single-crystal X-ray diffraction and further characterized by FT-IR, Rarnan spectra and DTA-TG. It crystallizes in the monoclinic system with space group P21/n, a=0.9036（2） nm, b=0.66052（18） nm, c=1.5997（4） nm, β=91.862（4）°, V=0.9543（4） nm^3 and Z=4. Its crystal structure consists of K-O polyhedra and 1-D stepped polyborate chains constructed by new [B6O9（OH）2]2- fundamental building blocks. 1-D polyborate chains contain 3,8-membered boron rings. Adjacent chains are further linked via H-bonding interactions into 2-D layers. The K^＋ cations reside not only between the layers but also in the 8-membered boron rings of the chains, compensating the negative charges of the borate chains and holding the layers together into the 3-D structure through bonding with oxygen atoms of the chains.     

High‐Pressure Synthesis and Single‐Crystal Structure Elucidation of the Indium Oxide‐Borate In4O2B2O7

The indium oxide‐borate In₄O₂B₂O₇ was synthesized under high‐pressure/high‐temperature conditions at 12.5 GPa/1420 K using a Walker‐type multianvil apparatus. Single‐crystal X‐ray structure elucidation showed edge‐sharing OIn₄ tetrahedra and B₂O₇ units building up the oxide‐borate. It crystallizes with Z = 8 in the monoclinic space group P2₁/n (no. 14) with a = 1016.54(3), b = 964.55(3), c = 1382.66(4) pm, and β = 109.7(1)°. The compound was also characterized by powder X‐ray diffraction and vibrational spectroscopy.     

Synthesis,Crystal Structure and Vibrational Spectroscopy of NH4[Co(NH3)5(H2O)][B4O5(OH)4]2·6H2O

A novel hydrated cobalt tetraborate complex NH₄[Co(NH₃)₅(H₂O)][B₄O₅(OH)₄]₂·6H₂O, was synthesized by the reaction of NH₄‐borate aqueous with CoCl₂ and its structure was determined by single crystal X‐ray diffraction. The crystal system of this complex is orthorhombic, the space group is Pnma, and the unit cell parameters are a=1.2901(2) nm, b=1.6817(3) nm, c=1.1368(2) nm, α=β=γ=90°, V=2.4742(8) nm³, and Z=4. This compound contains infinite borate layers constructed from [B₄O₅(OH)₄]^2? units via hydrogen bonds. The adjacent polyborate anion layers are further linked together with the octahedral [Co(NH₃)₅(H₂O)]³⁺ groups through hydrogen bonds to form 3D framework. The groups and guest water molecules are deposited in the empty space of this framework and interact with the layers by extensive hydrogen bonds. Infrared and Raman spectra (4000–400 cm^?1) of NH₄[Co(NH₃)₅(H₂O)][B₄O₅(OH)₄]₂·6H₂O were recorded at room temperature and analyzed. Fundamental vibrational modes were identified and band assignments were made. The middle band observed at 575 cm^?1 in Raman spectrum is the pulse vibration of [B₄O₅(OH)₄]^2?.     

Complex Borides RERu4B4 (RE = Ce,Pr, Nd,Sm) – Bonding Peculiarities and Magnetic Properties

The rare earth borides RERu₄B₄ (RE = Ce, Pr, Nd, Sm) were synthesized from the elements by arc‐melting and their crystal structures were studied on the basis of X‐ray powder and single‐crystal diffraction: LuRu₄B₄ type, I4₁/acd, a = 747.47(8), c = 1506.4(3) pm, wR₂ = 0.0579, 362 F² values for CeRu₄B₄, a = 751.3(2), c = 1507.1(5) pm, wR₂ = 0.0724, 471 F² values for PrRu₄B₄, a = 751.0(2), c = 1506.9(6) pm, wR₂ = 0.0598, 384 F² values for NdRu₄B₄, and a = 749.1(1), c = 1506.0(3) pm, wR₂ = 0.0759, 413 F² values for SmRu₄B₄, with 18 variables per refinement. Striking structural motifs of the RERu₄B₄ structures are Ru₄ tetrahedra and B₂ dumbbells with Ru–Ru and B–B distances of 271 and 180 pm in CeRu₄B₄. The intermediate valence of cerium leads to shorter Ce–Ru distances of 292 pm. CeRu₄B₄ behaves like a Pauli paramagnet with a small room temperature susceptibility of 1.5 × 10^–4 emu · mol^–1. Chemical bonding analyses shows substantial Ru–B and B–B bonding within the [Ru₄B₄] substructure.     

Syntheses,Crystal Structures,and Thermal Behaviors of Two New Metallo‐Organically Templated Pentaborates

Two new cadmium borates, [Cd(en)₃][B₅O₆(OH)₄]₂ · 2H₂O (en = ethylenediamine) ( 1 ) and [Cd(DETA)₂][B₅O₆(OH)₄]₂ (DETA = diethylenetriamine) ( 2 ) were synthesized in a novel procedure under mild solvothermal conditions and characterized by single‐crystal X‐ray diffraction, IR spectroscopy, elemental analysis, and TG–DTA. The compound 1 crystallizes in monoclinic system, space group P2₁/c (No. 14) with a = 8.526(2) Å, b = 23.127(6) Å, c = 15.438(4) Å, β = 94.320(3) °, V = 3035.5(13) Å³, Z = 4. Compound 2 is triclinic, space group P$\bar{1}$ (No. 2), a = 8.632(5) Å, b = 9.418(6) Å, c = 27.856(18) Å, α = 95.415(8) °, β = 91.891(7) °, γ = 93.563 (7) °, V = 2248(2) Å³, Z = 3. The anionic units of the both structures, [B₅O₆(OH)₄]^– are linked by hydrogen bonds to form a three‐dimensional framework with large channels, in which the templating cadmium complex cations are located. The thermal decomposition performance of compound 1 requires three steps, whereas only two steps are needed for compound 2 , which all lead to amorphous phases. These processes are well explained considering the structure and the change in the Cd²⁺ coordination during heating.     

Syntheses,Characterizations, and Crystal Structures of Two New Organically Templated Borates

Two new organically templated borates, [H₂DAB][B₇O₉(OH)₅]·2H₂O ( 1 ) and [H₂DAB][B₇O₁₀(OH)₃] ( 2 ), have been synthesized under mild conditions in the presence of DAB acting as structure‐directing agent (DAB = 1,4‐diaminobutane). The structures were determined by single crystal X‐ray diffraction and further characterized by FTIR, elemental analysis, and thermogravimetric analysis. Both 1 and 2 crystallize in the same triclinic system, space group (No. 2); 1: a = 8.238(4) Å, b = 8.348 (5) Å, c = 14.574(8) Å, a = 101.050(3)°, β = 92.313(7)°, γ = 112.694(5)°, V = 900.3(8) ų, Z = 2; 2: a = 8.8769(3) Å, b = 9.3204(2) Å, c = 10.2204(5) Å, α = 74.474(2)°, β = 85.292(5)°, γ = 72.730(2)°, V = 778.01(5) ų, Z = 2. The structure of 1 consists of [B₇O₉(OH)₅]^2? groups, which represents the first example of organically templated heptaborate. The structure exhibits interesting hydrogen‐bonded network formed by borate polyanion [B₁₄O₂₀(OH)₆]^4?, which can be regarded as being constructed from the dehydration of the FBBs in 1 . The diprotonated organic amines are filled in the free space of the hydrogen‐bonded network and interact with the inorganic framework by extensive hydrogen bonds.     

Pb2(OH)2[p‐O2C‐C6H4‐CO2]: Synthese und Kristallstruktur

Pb₂(OH)₂[p‐O₂C‐C₆H₄‐CO₂]: Synthesis and Crystal Structure Single crystals of Pb₂(OH)₂[p‐O₂C‐C₆H₄‐CO₂] ( 1 ) were obtained by hydrothermal reaction of terephthalic acid and PbCO₃ at 180 °C (10 days). 1 crystallizes in the monoclinic space group P2₁/c with Z = 2 (a = 1115.6(2) pm, b = 380.10(4) pm, c = 1141.3(2) pm, β = 93.39(1)°, V = 0.4831(1) nm³). The crystal structure is characterized by ladder‐type Pb(OH)_3/3 double chains, which are connected to a three‐dimensional framework by terephthalate dianions.     

High‐Pressure Synthesis and Characterization of New Actinide Borates,AnB4O8 (An=Th,U)

New actinide borates ThB₄O₈ and UB₄O₈ were synthesized under high‐pressure, high‐temperature conditions (5.5 GPa/1100 °C for thorium borate, 10.5 GPa/1100 °C for the isotypic uranium borate) in a Walker‐type multianvil apparatus from their corresponding actinide oxide and boron oxide. The crystal structure was determined on basis of single‐crystal X‐ray diffraction data that were collected at room temperature. Both compounds crystallized in the monoclinic space group C2/c (Z=4). Lattice parameters for ThB₄O₈: a=1611.3(3), b=419.86(8), c=730.6(2) pm; β=114.70(3)°; V=449.0(2) ų; R₁=0.0255, wR₂=0.0653 (all data). Lattice parameters for UB₄O₈: a=1589.7(3), b=422.14(8), c=723.4(2) pm; β=114.13(3)°; V=443.1(2) ų; R₁=0.0227, wR₂=0.0372 (all data). The new AnB₄O₈ (An=Th, U) structure type is constructed from corner‐sharing BO₄ tetrahedra, which form layers in the bc plane. One of the four independent oxygen atoms is threefold‐coordinated. The actinide cations are located between the boron–oxygen layers. In addition to Raman spectroscopic investigations, DFT calculations were performed to support the assignment of the vibrational bands.     

Rb2Co3(H2O)2[B4P6O24(OH)2]: Ein Borophosphat mit ‐Tetraeder‐Anionenteilstruktur und Oktaeder‐Trimeren (CoO12(H2O)2)

Rb₂Co₃(H₂O)₂[B₄P₆O₂₄(OH)₂]: A Borophosphate with ‐Tetrahedral Anionic Partial Structure and Trimers of Octahedra (Co O₁₂(H₂O)₂) Rb₂Co₃(H₂O)₂[B₄P₆O₂₄(OH)₂] is formed under mild hydrothermal conditions (T = 165 °C) from mixtures of RbOH_(aq), CoCl₂, H₃BO₃, and H₃PO₄ (molar ratio 1 : 1 : 1 : 2). The crystal structure (orthorhombic system) was solved by X‐ray single crystal methods (space group Pbca, No. 61; R‐values (all data): R1 = 0.0699, wR2 = 0.0878): a = 950.1(1) pm, b = 1227.2(2) pm, c = 2007.4(2) pm; Z = 4. The anionic partial structure consists of tetrahedral [B₄P₆O₂₄(OH)₂^8–] layers, which contain three‐ and nine‐membered rings. Co^II is octahedrally coordinated by oxygen and oxygen and H₂O ligands, respectively (coordination octahedra CoO₆ and CoO₄(H₂O)₂). Three adjacent coordination octahedra are condensed via common edges to form trimeric units (CoO₁₂(H₂O)₂). The oxidation state +2 of cobalt was confirmed by magnetic measurements. The octahedral trimers are quasi‐isolated. No long‐range magnetic ordering occurs down to 2 K. Rb⁺ is disordered over three crystallographically independent sites within channels of the structure running parallel [010]; the coordination sphere of Rb⁺ is formed by nine oxygen species of the tetrahedral layers, one OH group and one H₂O molecule.     

Synthesis, characterization and thermochemistry of K2B5O8(OH)·2H2O

A pure hydrated potassium borate K₂B₅O₈(OH)·2H₂O has been synthesized under mild hydrothermal conditions and characterized by single-crystal X-ray diffraction, XRD, FT-IR, Raman spectra and DTA-TG. The crystal structure consists of two K-O polyhedra and [B₅O₈(OH)]²⁻ polyborate anion. The enthalpy of formation was determined to be −4772.6 ± 4.0 kJ mol⁻¹ by solution calorimetry.