Synthese und Kristallstruktur von Terbium(III)‐meta‐Oxoborat Tb(BO2)3 (≡ TbB3O6)

Synthesis and Crystal Structure of Terbium(III) meta‐Oxoborate Tb(BO₂)₃ (≡ TbB₃O₆) The terbium meta‐oxoborate Tb(BO₂)₃ (≡ TbB₃O₆) is obtained as single crystals by the reaction of terbium, Tb₄O₇ and TbCl₃ with an excess of B₂O₃ in gastight sealed platinum ampoules at 950 °C after three weeks. The compound appears to be air‐ and water‐resistant and crystallizes as long, thin, colourless needles which tend to growth‐twinning due to their marked fibrous habit. The crystal structure of Tb(BO₂)₃ (orthorhombic, Pnma; a = 1598.97(9), b = 741.39(4), c = 1229.58(7) pm; Z = 16) contains strongly corrugated oxoborate layers {(BO₂)^‐} built of vertex‐linked [BO₄]^5‐ tetrahedra (d(B‐O) = 143 ‐ 154 pm, ?(O‐B‐O) = 102‐115°) which spread out parallel (100). The four crystallographically different Tb³⁺ cations all exhibit coordination numbers of eight towards the oxygen atoms (d(Tb‐O) = 228‐287 pm). The corresponding metal cation polyhedra [TbO₈]¹³⁺ too convene to layers (composition: {(Tb₂O₁₁)^16‐}) which are likewise oriented parallel to the (100) plane.     

La3OCl[AsO3]2: Ein Lanthan‐Oxidchlorid‐Oxoarsenat(III) mit “lone‐pair”‐Kanalstruktur

La₃OCl[AsO₃]₂: A Lanthanum Oxide Chloride Oxoarsenate(III) with a “Lone‐Pair” Channel Structure La₃OCl[AsO₃]₂ was prepared by the solid‐state reaction between La₂O₃ and As₂O₃ using LaCl₃ and CsCl as fluxing agents in evacuated silica ampoules at 850 °C. The colourless crystals with pillar‐shaped habit crystallize tetragonally (a = 1299.96(9), c = 558.37(5) pm, c/a = 0.430) in the space group P4₂/mnm (no. 136) with four formula units per unit cell. The crystal structure contains two crystallographically different La³⁺ cations. (La1)³⁺ is coordinated by six oxygen atoms and two chloride anions in the shape of a bicapped trigonal prism (CN = 8), whereas (La2)³⁺ carries eight oxygen atoms and one Cl^? anion arranged in the shape of tricapped trigonal prism (CN = 9). The isolated pyramidal [AsO₃]^3? anions (d(As–O) = 175–179 pm) consist of three oxygen atoms (O2 and two O3), which surround the As³⁺ cations together with the free, non‐binding electron pair (lone pair) Ψ¹‐tetrahedrally (?(O–As–O) = 95°, 3×). One of the three crystallographically independent oxygen atoms (O1), however, is exclusively coordinated by four (La2)³⁺ cations in the shape of a real tetrahedron (d(O–La) = 236 pm, 4×). These [(O1)(La2)₄]¹⁰⁺ tetrahedra form endless chains in the direction of the c axis through trans‐edge condensation. Empty channels, constituted by the lone‐pair electrons of the Cl^? anions and the As³⁺ cations in the Ψ¹‐tetrahedral oxoarsenate(III) anions [AsO₃]^3?, run parallel to [001] as well.     

Über den H‐ und A‐Typ von La2[Si2O7]

On the H‐ and A‐Type Structure of La₂[Si₂O₇] By thermal decomposition of La₃F₃[Si₃O₉] at 700 °C in a CsCl flux single crystals of a new form of La₂[Si₂O₇] have been found which is called H type (triclinic, P1; a = 681.13(4), b = 686.64(4), c = 1250.23(8) pm, α = 82.529(7), β = 88.027(6), γ = 88.959(6)°; V_m = 87.223(9) cm³/mol, D_x = 5.113(8) g/cm³, Z = 4) continuing Felsche's nomenclature. It crystallizes isotypically to the triclinic K₂[Cr₂O₇] in a structure closely related to that of A–La₂[Si₂O₇] (tetragonal, P4₁; a = 683.83(7), c = 2473.6(4) pm; V_m = 87.072(9) cm³/mol, D_x = 5.122(8) g/cm³, Z = 8). For comparison, the latter has been refined from single crystal data, too. Both the structures can be described as sequence of layers of each of two crystallographically different [Si₂O₇]^6– anions always built up of two corner‐linked [SiO4] tetrahedra in eclipsed conformation with non‐linear Si–O–Si bridges (∢(Si–O–Si) = 128–132°) piled up in [001] direction and aligned almost parallel to the c axis. They differ only in layer sequence: Whereas the double tetrahedra of the disilicate units are tilted alternating to the left and in view direction ([010]; stacking sequence: AB) in H–La₂[Si₂O₇], after layer B there follow due to the 4₁ screw axis layers with anions tilted to the right and tilted against view direction ([010]; stacking sequence: ABA′B′) in A–La₂[Si₂O₇]. The extremely irregular coordination polyhedra around each of the four crystallographically independent La³⁺ cations in both forms (H and A type) consist of eight to ten oxygen atoms in spacing intervals of 239 to 330 pm. The possibility of more or less ordered intermediate forms will be discussed.     

Er2S[SiO4]: Ein Erbiumsulfid‐ortho‐Oxosilicat mit ungewöhnlicher Sulfidionen‐Koordination

During the reaction of cadmium sulfide with erbium and sulfur in evacuated silica ampoules pink lath‐shaped crystals of Er₂S[SiO₄] occur as by‐product which were characterized by X‐ray single crystal structure analysis. The title compound crystallizes orthorhombically in the space group Cmce (a = 1070.02(8), b = 1235.48(9), c = 683.64(6) pm) with eight formula units per unit cell. Besides isolated ortho‐oxosilicate units [SiO₄]^4?, the crystal structure contains two crystallographically independent Er³⁺ cations which are both eightfold coordinated by six oxygen and two sulfur atoms. The sulfide anions are surrounded by four erbium cations each in the shape of very distorted tetrahedra. These excentric [SEr₄]¹⁰⁺ tetrahedra build up layers according to by vertex‐ and edge‐connection. They are piled parallel to (010) and separated by the isolated ortho‐oxosilicate tetrahedra.     

Sm2As4O9: Ein ungewöhnliches Samarium(III)‐Oxoarsenat(III) gemäß Sm4[As2O5]2[As4O8]

Sm₂As₄O₉: An Unusual Samarium(III) Oxoarsenate(III) According to Sm₄[As₂O₅]₂[As₄O₈] Pale yellow single crystals of the new samarium(III) oxoarsenate(III) with the composition Sm₄As₈O₁₈ were obtained by a typical solid‐state reaction between Sm₂O₃ and As₂O₃ using CsCl and SmCl₃ as fluxing agents. The compound crystallizes in the triclinic crystal system with the space group (No. 2, Z = 2; a = 681.12(5), b = 757.59(6), c = 953.97(8) pm, α = 96.623(7), β = 103.751(7), γ = 104.400(7)°). The crystal structure of samarium(III) oxoarsenate(III) with the formula type Sm₄[As₂O₅]₂[As₄O₈] (≡ 2 × Sm₂As₄O₉) contains two crystallographically different Sm³⁺ cations, where (Sm1)³⁺ is coordinated by eight, but (Sm2)³⁺ by nine oxygen atoms. Two different discrete oxoarsenate(III) anions are present in the crystal structure, namely [As₂O₅]^4? and [As₄O₈]^4?. The [As₂O₅]^4? anion is built up of two Ψ¹‐tetrahedra [AsO₃]^3? with a common corner, whereas the [As₄O₈]^4? anion consists of four Ψ¹‐tetrahedra with ring‐shaped vertex‐connected [AsO₃]^3? pyramids. Thus at all four crystallographically different As³⁺ cations stereochemically active non‐binding electron pairs (“lone pairs”) are observed. These “lone pairs” direct towards the center of empty channels running parallel to [010] in the overall structure, where these “empty channels” being formed by the linkage of layers with the ecliptically conformed [As₂O₅]^4? anions and the stair‐like shaped [As₄O₈]^4? rings via common oxygen atoms (O1 – O6, O8 and O9). The oxygen‐atom type O7, however, belongs only to the cyclo‐[As₄O₈]^4? unit as one of the two different corner‐sharing oxygen atoms.     

La2Si2O7 im I—Typ: Gemäß La6[Si4O13][SiO4]2 kein echtes Lanthandisilicat

I‐Type La₂Si₂O₇: According to La₆[Si₄O₁₃][SiO₄]₂ not a Real Lanthanum Disilicate In attempts to synthesize lanthanum telluride silicate La₂Te[SiO₄] (from La, TeO₂, SiO₂ and CsCl, molar ratio: 1 : 1: 1 : 20, 950 °C, 7 d) or fluoride‐rich lanthanum fluoride silicates (from LaF₃, La₂O₃, SiO₂ and CsCl, molar ratio: 5 : 2 : 3 : 17, 700 °C, 7 d) in evacuated silica tubes, colourless lath‐shaped single crystals of hitherto unknown I‐type La₂Si₂O₇ (monoclinic, P2₁/c; a = 726.14(5), b = 2353.2(2), c = 1013.11(8) pm, β = 90.159(7)°) were found in the CsCl‐flux melts. Nevertheless, this new modification of lanthanum disilicate does not contain any discrete disilicate groups [Si₂O₇]^6‐ but formally three of them are dismutated into one catena‐tetrasilicate ([Si₄O₁₃]^10‐ unit of four vertex‐linked [SiO₄]^4‐ tetrahedra) and two ortho‐silicate anions (isolated [SiO₄]^4‐ tetrahedra) according to La₆[Si₄O₁₃][SiO₄]₂. This compound can be described as built up of alternating layers of these [SiO₄]^4‐ and the horseshoe‐shaped [Si₄O₁₃]^10‐ anions along [010]. Between and within the layers the high‐coordinated La ³⁺ cations (CN = 9 ‐ 11) are localized. The close structural relationship to the borosilicates M₃[BSiO₆][SiO₄](M = Ce ‐ Eu) is discussed and structural comparisons with other catena‐tetrasilicates are presented.     

Synthese und Kristallstruktur des Fluorid‐ino‐Oxosilicats Cs2YFSi4O10

Synthesis and Crystal Structure of the Fluoride ino‐Oxosilicate Cs₂YFSi₄O₁₀ The novel fluoride oxosilicate Cs₂YFSi₄O₁₀ could be synthesized by the reaction of Y₂O₃, YF₃ and SiO₂ in the stoichiometric ratio 2 : 5 : 3 with an excess of CsF as fluxing agent in gastight sealed platinum ampoules within seventeen days at 700 °C. Single crystals of Cs₂YFSi₄O₁₀ appear as colourless, transparent and water‐resistant needles. The characteristic building unit of Cs₂YFSi₄O₁₀ (orthorhombic, Pnma (no. 62), a = 2239.75(9), b = 884.52(4), c = 1198.61(5) pm; Z = 8) comprises infinite tubular chains of vertex‐condensed [SiO₄]^4? tetrahedra along [010] consisting of eight‐membered half‐open cube shaped silicate cages. The four crystallographically different Si⁴⁺ cations all reside in general sites 8d with Si–O distances from 157 to 165 pm. Because of the rigid structure of this oxosilicate chain the bridging Si–O–Si angles vary extremely between 128 and 167°. The crystallographically unique Y³⁺ cation (in general site 8d as well) is surrounded by four O^2? and two F^? anions (d(Y–O) = 221–225 pm, d(Y–F) = 222 pm). These slightly distorted trans‐[YO₄F₂]^7? octahedra are linked via both apical F^? anions by vertex‐sharing to infinite chains along [010] (?(Y–F–Y) = 169°, ?(F–Y–F) = 177°). Each of these chains connects via terminal O^2? anions to three neighbouring oxosilicate chains to build up a corner‐shared, three‐dimensional framework. The resulting hexagonal and octagonal channels along [010] are occupied by the four crystallographically different Cs⁺ cations being ten‐, twelve‐, thirteen‐ and fourteenfold coordinated by O^2? and F^? anions (viz.[(Cs1)O₁₀]^19?, [(Cs2)O₁₀F₂]^21?, [(Cs3)O₁₂F]^24?, and [(Cs4)O₁₂F₂]^25? with d(Cs–O) = 309–390 pm and d(Cs–F) = 360–371 pm, respectively).     

Einkristalle von La[AsO4] im Monazit‐ und Sm[AsO4] im Xenotim‐Typ

Single Crystals of La[AsO₄] with Monazite‐ and Sm[AsO₄] with Xenotime‐Type Structure Brick‐shaped, transparent single crystals of colourless monazite‐type La[AsO₄] (monoclinic, P2₁/n, a = 676.15(4), b = 721.03(4), c = 700.56(4) pm, β =104.507(4)°, Z = 4) and pale yellow xenotime‐type Sm[AsO₄] (tetragonal, I4₁/amd, a = 718.57(4), c = 639.06(4) pm, Z = 4) emerge as by‐products from alkali and rare‐earth metal chloride fluxes whenever the synthesis of lanthanide(III) oxoarsenate(III) derivatives from admixtures of the corresponding sesquioxides in sealed, evacuated silica ampoules is accompanied by air intrusion and subsequent oxidation. Nine oxygen atoms from seven discrete [AsO₄]^3? tetrahedra recruit the rather irregular coordination sphere of La³⁺ (d(La³⁺?O^2?) = 248 – 266 pm plus 291 pm) and even a tenth ligand could be considered at a distance of 332 pm. The trigonal dodecahedral figure of coordination consisting of eight oxygen atoms at distances of 236 and 248 pm (4× each) about Sm³⁺ is provided by only six isolated tetrahedral [AsO₄]^3? units. Alternating trans‐edge condensation of the latter with the [LaO₉₊₁] polyhedra of monazite‐type La[AsO₄] and the [SmO₈] polyhedra of xenotime‐type Sm[AsO₄] constitutes the main structural chain features along [100] or [001], respectively. The bond distances and angles of the complex [AsO₄]^3? anions range within common intervals (d(As⁵⁺?O^2?) = 167 – 169 pm, ?(O–As–O) = 100 – 116°) for both lanthanide(III) oxoarsenates(V) presented here.     

Thiosilicate der Selten‐Erd‐Elemente: III. KLa[SiS4] und RbLa[SiS4] – Ein struktureller Vergleich

Thiosilicates of the Rare‐Earth Elements: III. KLa[SiS₄] and RbLa[SiS₄] – A Structural Comparison Pale yellow, platelet shaped, air‐ and water resistant single crystals of KLa[SiS₄] derived from the reaction of lanthanum (La) and sulfur (S) with silicon disulfide (SiS₂) in a molar ratio of 2 : 3 : 1 with an excess of potassium chloride (KCl) as flux and source of potassium ions in evacuated silica ampoules at 850 °C within seven days. The analogous reaction utilizing a melt of rubidium chloride (RbCl) instead also leads to yellow comparable single crystals of RbLa[SiS₄]. The potassium lanthanum thiosilicate crystallizes monoclinically with the space group P2₁/m (a = 653.34(6), b = 657.23(6), c = 867.02(8) pm, β = 107.496(9)°) and two formula units per unit cell, while the rubidium lanthanum thiosilicate has to be assigned orthorhombically with the space group Pnma (a = 1728.4(2), b = 667.23(6), c = 652.89(6) pm) and four formula units in its unit cell. In both compounds the La³⁺ cations are surrounded by 8+1 sulfide anions in the shape of tricapped trigonal prisms. The Rb⁺ cations in RbLa[SiS₄] show a coordination number of 9+2 relative to the S^2? anions, which form pentacapped trigonal prisms about Rb⁺. This coordination number, however, is apparently too high for the K⁺ cations in KLa[SiS₄], so that they only exhibit a bicapped trigonal prismatic environment built up by eight S^2? anions. The isolated thiosilicate tetrahedra [SiS₄]^4? of the rubidium compound are surrounded by La³⁺ both edge‐ and face‐capping, but terminal as well as edge‐ and face‐spanning by Rb⁺. In the potassium compound there is no change for the La³⁺ environment about the [SiS₄]^4? tetrahedra, but the K⁺ cations are only able to attach terminal and via edges. The whole structure is built up by anionic equation/tex2gif-stack-1.gif{La[SiS₄]}^? layers that are separated by the alkali metal cations. In direct comparison the two thiosilicate structures can be regarded as stacking variants.     

Das Lanthan‐Dodekahydro‐closo‐Dodekaborat‐Hydrat [La(H2O)9]2[B12H12]3·15 H2O und sein Oxonium‐Chlorid‐Derivat [La(H2O)9](H3O)Cl2[B12H12]·H2O

The Lanthanum Dodecahydro‐closo‐Dodecaborate Hydrate [La(H₂O)₉]₂[B₁₂H₁₂]₃·15 H₂O and its Oxonium‐Chloride Derivative [La(H₂O)₉](H₃O)Cl₂[B₁₂H₁₂]·H₂O By neutralization of an aqueous solution of the free acid (H₃O)₂[B₁₂H₁₂] with basic La₂O₃ and after isothermic evaporation colourless, face‐rich single crystals of a water‐rich lanthanum(III) dodecahydro‐closo‐dodecaborate hydrate [La(H₂O)₉]₂[B₁₂H₁₂]₃·15 H₂O are isolated. The compound crystallizes in the trigonal system with the centrosymmetric space group (a = 1189.95(2), c = 7313.27(9) pm, c/a = 6.146; Z = 6; measuring temperature: 100 K). The crystal structure of [La(H₂O)₉]₂[B₁₂H₁₂]₃·15 H₂O can be characterized by two of each other independent, one into another posed motives of lattice components. The [B₁₂H₁₂]²⁻ anions (d(B–B) = 177–179 pm; d(B–H) = 105–116 pm) are arranged according to the samarium structure, while the La³⁺ cations are arranged according to the copper structure. The lanthanum cations are coordinated in first sphere by nine oxygen atoms from water molecules in form of a threecapped trigonal prism (d(La–O) = 251–262 pm). A coordinative influence of the [B₁₂H₁₂]²⁻ anions on La³⁺ has not been determined. Since “zeolitic” water of hydratation is also present, obviously the classical H–O^δ–···^+δH–O‐hydrogen bonds play a significant role in the stabilization of the crystal structure. During the conversion of an aqueous solution of (H₃O)₂[B₁₂H₁₂] with lanthanum trichloride an anion‐mixed salt with the composition [La(H₂O)₉](H₃O)Cl₂[B₁₂H₁₂]·H₂O is obtained. The compound crystallizes in the hexagonal system with the non‐centrosymmetric space group (a = 808.84(3), c = 2064.51(8) pm, c/a = 2.552; Z = 2; measuring temperature: 293 K). The crystal structure can be characterized as a layer‐like structure, in which [B₁₂H₁₂]²⁻ anions and H₃O⁺ cations alternate with layers of [La(H₂O)₉]³⁺ cations (d(La–O) = 252–260 pm) and Cl⁻ anions along [001]. The [B₁₂H₁₂]²⁻ (d(B–B) = 176–179 pm; d(B–H) = 104–113 pm) and Cl⁻ anions exhibit no coordinative influence on La³⁺. Hydrogen bonds are formed between the H₃O⁺ cations and [B₁₂H₁₂]²⁻ anions, also between the water molecules of [La(H₂O)₉]³⁺ and Cl⁻ anions, which contribute to the stabilization of the crystal structure.     

LaCl(BO2)2 und Er2Cl2[B2O5]: Zwei Chlorid‐Oxoborate dreiwertiger Lanthanide

LaCl(BO₂)₂ and Er₂Cl₂[B₂O₅]: Two Chloride Oxoborates of Trivalent Lanthanides Er₂Cl₂[B₂O₅] is obtained as single crystals by the reaction of ErCl₃, Er₂O₃ and B₂O₃ with an excess of ErCl₃ as flux in evacuated silica tubes after two weeks at 850 °C. The compound crystallizes as long, pale pink needles and appears to be air‐ and water‐resistant. Single‐crystalline LaCl(BO₂)₂ emerges from the reaction of La₂O₃, LaCl₃, and B₂O₃ with an excess of B₂O₃ as flux in evacuated silica tubes after four weeks at 900 °C. LaCl(BO₂)₂ crystallizes as thin, colourless, air‐ and water‐resistant needles which tend to severe twinning due to their fibrous habit. The crystal structure of Er₂Cl₂[B₂O₅] (orthorhombic, Pbam; a = 1489.65(9), b = 1004.80(6), c = 524.86(3) pm; Z = 4) contains two crystallographically different erbium cations. (Er1)³⁺ resides in pentagonal‐bipyramidal coordination of seven anions while (Er2)³⁺ is surrounded by only six anions with the shape of an octahedron. The planar oxodiborate units [B₂O₅]^4— consisting of two vertex‐shared [BO₃]^3— triangles are isolated according to {([BOO]₂)^4—}. LaCl(BO₂)₂ crystallizes isostructurally with PrCl(BO₂)₂ in the triclinic space group P1¯ (a = 423.52(4), b = 662.16(7), c = 819.33(8) pm; α = 82.081(8), β = 89.238(9), γ = 72.109(7)°; Z = 2). The characteristic unit consists of endless chains built up by corner‐linked [BO₃]^3— triangles. These quasi‐planar zigzag chains of the composition {[(B1)OO(B2)OO]^2—} (≡ {[BO₂]^—} run parallel [100]. The La³⁺ cations exhibit coordination numbers of ten and are coordinated by three Cl^— and seven O^2— anions.     

[O2Pb3]2(BO3)Br: An Oxidoborate Oxide Bromide with the ∞1[O2Pb3] Double Chains Based on Edge‐sharing OPb4 Tetrahedra

Through extensive research on the PbO / PbBr₂ / B₂O₃ system, a new single crystal of yellow lead‐containing oxyborate bromine, [O₂Pb₃]₂(BO₃)Br, was grown from the melt. It crystallizes in the centrosymmetric space group Cmcm (no. 63) of the orthorhombic system with the following unit cell dimensions: a = 9.5748(8) Å, b = 20.841(2) Å, c = 5.7696(5) Å, and Z = 4. The whole structure is characterized by an infinite one‐dimensional (1D) _∞¹[O₂Pb₃] double chain, which is based on the OPb₄ oxocentered tetrahedra and considered as the derivative of the continuous sheet of OPb₄ tetrahedra from the tetragonal modification of α‐PbO. The 1D _∞¹[O₂Pb₃] double chains are further bridged by the BO₃ units through common oxygen atoms to form two‐dimensional (2D) _∞¹[[(O₂Pb₃)(BO₃)] layers, with Br atoms situated between the layers. IR spectroscopy, UV/Vis/NIR diffuse reflectance spectroscopy, and thermal analysis were also performed on the reported material.     

La4N2S3: Ein neues Nitridsulfid des Lanthans mit beispielloser Kristallstruktur

La₄N₂S₃: A New Nitride Sulfide of Lanthanum with Unprecedented Crystal Structure The oxidation of lanthanum powder with sulfur and cesium azide (CsN₃) in the presence of lanthanum tribromide (LaBr₃) yields lanthanum nitride sulfide with the composition La₄N₂S₃ when appropriate molar ratios of the reactants are used. Additional cesium bromide (CsBr) as a flux secures fast reactions (7 d) at 900 °C in evacuated silica tubes as well as the formation of almost black single crystals. The orthorhombic crystal structure (Pnnm, Z = 2) was determined from single crystal X‐ray diffraction data (a = 641.98(4), b = 1581.42(9), c = 409.87(3) pm). Two crystallographically different La³⁺ cations are present, La1 resides in sixfold coordination of two N^3? and four S^2? anions forming a trigonal prism and La2 is coordinated by two N^3? and five S^2? in the shape of a monocapped trigonal prism. However, the main feature of the crystal structure comprises N^3?‐centred (La³⁺)₄ tetrahedra which arrange as pairs [N₂La₆]¹²⁺ of edge‐shared [NLa₄]⁹⁺ units and which are further connected via four vertices to form double chains . They get bundled along [001] like a hexagonal rod packing and are held together by two crystallographically different S^2? anions. Further motifs for the connectivity of [NM₄]⁹⁺ tetrahedra in crystal structures of nitride chalcogenides and halides of the rare‐earth elements (M = Sc, Y, La; Ce – Lu) with ratios of N : M = 1 : 2 are presented and discussed for comparison.     

Li2Eu3Br2[BO3]2: A New Europium(II) Halide Oxoborate with Yellow Luminescence

The europium(II) oxoborate Li₂Eu₃Br₂[BO₃]₂ featuring lithium and bromide ions was synthesized by the reaction of Eu₂O₃ with Li[BH₄] as lithium- and boron- as well as EuBr₃ as bromide-source at 750 °C for 24 h in silica-jacketed sealed niobium capsules. The yellow, air-stable and yellow fluorescent compound crystallizes in the trigonal space group R3 m (a = 1049.06(7) pm, c = 2993.1(3) pm, c/a = 2.853, Z = 12). The two crystallographically distinguishable Eu²⁺ cations show either an eightfold coordination as bicapped trigonal prism ([EuO₆Br₂]^12–) or a ninefold coordination as monocapped square antiprism ([EuO₅Br₄]^12–). All oxygen atoms stem from isolated triangular [BO₃]^3– anions and the Li⁺ cations reside in octahedral voids provided by both oxygen atoms and Br^– anions.     

Einkristalle des Cer(III)‐Borosilicats Ce3[BSiO6][SiO4]

Single Crystals of the Cerium(III) Borosilicate Ce₃[BSiO₆][SiO₄] Colorless, lath‐shaped single crystals of Ce₃[BSiO₆]‐ [SiO₄] (orthorhombic, Pbca; a = 990.07(6), b = 720.36(4), c = 2329.2(2) pm, Z = 8) were obtained in attempts to synthesize fluoride borates with trivalent cerium in evacuated silica tubes by reaction of educt mixtures of elemental cerium, cerium dioxide, cerium trifluoride, and boron sesquioxide (Ce, CeO₂, CeF₃, B₂O₃; molar ratio 3 : 1 : 3 : 3) in fluxing CsCl (700 °C, 7 d) with the glass wall. The crystal structure contains eight‐ (Ce1) and ninefold coordinated Ce³⁺ cations (Ce2 and Ce3) surrounded by oxygen atoms. Charge balance is achieved by both discrete borosilicate ([BSiO₆]^5– ≡ [O₂BOSiO₃]^5–) and ortho‐silicate anions ([SiO₄]^4–). The former consists of a [BO₃] triangle linked to a [SiO₄] tetrahedron by a single vertex. The anions form layers in [001] direction alternatingly built up from [BSiO₆]^5– and [SiO₄]^4– groups while Ce³⁺ cations are located in between.     

Rb6LiPr11Cl16[SeO3]12: Ein chloridisch derivatisiertes Rubidium‐Lithium‐Praseodym(III)‐Oxoselenat(IV)

Rb₆LiPr₁₁Cl₁₆[SeO₃]₁₂: A Chloride‐Derivatized Rubidium Lithium Praseodymium(III) Oxoselenate(IV) Transparent green square platelets with often truncated edges and corners of Rb₆LiPr₁₁Cl₁₆[SeO₃]₁₂ were obtained by the reaction of elemental praseodymium, praseodymium(III,IV) oxide and selenium dioxide with an eutectic LiCl–RbCl flux at 500 °C in evacuated silica ampoules. A single crystal of the moisture and air insensitive compound was characterized by X‐ray diffraction single‐crystal structure analysis. Rb₆LiPr₁₁Cl₁₆[SeO₃]₁₂ crystallizes tetragonally in the space group I4/mcm (no. 140; a = 1590.58(6) pm, c = 2478.97(9) pm, c/a = 1.559; Z = 4). The crystal structure is characterized by two types of layers parallel to the (001) plane following the sequence 121′2′1. Cl^? anions form cubes around the Rb⁺ cations (Rb1 and Rb2; CN = 8; d(Rb⁺?Cl^?) = 331 – 366 pm) within the first layer. One quarter of the possible places for Rb⁺ cations within this CsCl‐type kind of arrangement is not occupied, however the Cl^? anions of these vacancies are connected to Pr³⁺ cations (Pr4) above and below instead, forming square antiprisms of [(Pr4)O₄Cl₄]^9? units (d(Pr4?O) = 247–249 pm; d(Pr4?Cl) = 284–297 pm) that work as links between layer 1 and 2. Central cations of the second layer consist of Li⁺ and Pr³⁺. While the Li⁺ cations are surrounded by eight O^2? anions (d(Li?O5) = 251 pm) in the shape of cubes again, the Pr³⁺ cations are likewisely coordinated by eight O^2? anions as square antiprisms (for Pr1, d(Pr1?O2) = 242 pm) and by ten O^2? anions (for Pr2 and Pr3), respectively. The latter form tetracapped trigonal antiprisms (Pr2, d(Pr2?O) = 251–253 pm and 4 × 262 pm) or bicapped distorted cubes (Pr3, d(Pr3?O) = 245–259 pm and 2 × 279 pm). The non‐binding electron pairs (“lone pairs”) at the two crystallographically different Ψ¹‐tetrahedral [SeO₃]^2? anions (d(Se⁴⁺?O^2?) = 169–173 pm) are directing towards the empty cavities between the layer‐connecting [(Pr4)O₄Cl₄]^9? units.     

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).     

Ho2O[SiO4] und Ho2S[SiO4]: Zwei Chalkogenid‐Derivate von Holmium(III)‐ortho‐ Oxosilicat

Ho₂O[SiO₄] and Ho₂S[SiO₄]: Two Chalcogenide Derivatives of Holmium(III) ortho‐Oxosilicate Ho₂O[SiO₄] crystallizes monoclinically with the space group P2₁/c (a = 904.15(9), b = 688.93(7), c = 667.62(7) pm, β = 106.384(8)°, Z = 4) in the A‐type structure of rare‐earth(III) oxide oxosilicates. Yellow platelet‐shaped single crystals were obtained as by‐product during an experiment to synthesize Ho₃Cl[SiO₄]₂ by reacting Ho₂O₃ and SiO₂ in the ratio 4 : 6 with an excess of HoCl₃ as flux at 1000 °C for seven days in evacuated silica ampoules. Both crystallographically different Ho³⁺ cations show coordination numbers of 8+1 and 7 with coordination figures of 2+1‐fold capped trigonal prisms and octahedra, in which one of the vertices changes to an edge by two instead of one coordinating atoms, respectively. The O^2— anion not linked to silicon is surrounded tetrahedrally by four Ho³⁺ cations which built a layer parallel (100) by vertex‐ and edge‐sharing of the [OHo₄]¹⁰⁺ units according to {[(O5)(Ho1)_1/1(Ho2)_3/3]⁴⁺}. Within rhombic meshes of these layers the isolated oxosilicate tetrahedra [SiO₄]^4— come to lie. Ho₂S[SiO₄] crystallizes orthorhombically in the space group Pbcm (a = 605.87(5), b = 690.41(6), c = 1064.95(9) pm, Z = 4). It also emerged as a single‐crystalline by‐product obtained during the synthesis of Ho₂OS₂ by reaction of a mixture of Ho₂O₃, Ho and S with the wall of the evacuated silica tube used as container with an excess of CsCl as flux at 800 °C. The structure of the yellow platelet‐shaped, air and water resistant crystals also distinguishes two Ho³⁺ cations with bicapped trigonal prisms and trigondodecahedra as coordination polyhedra for CN = 8. The S^2— anions are almost square planar surrounded by four Ho³⁺ cations, but situated completely outside this plane. The [SHo₄]¹⁰⁺ squares form strongly corrugated layers perpendicular to [100] by corner‐sharing according to {[(S)(Ho1)_2/2(Ho2)_2/2]⁴⁺}. Contrary to the oxide oxosilicates the isolated oxosilicate tetrahedra [SiO₄]^4— do not lie within the rhombic meshes of these layers, but above and below the (Ho2)³⁺ cations while viewing along [100].     

Pr(BO2)3 und PrCl(BO2)2: Zwei meta‐Borate des Praseodyms im Vergleich

Pr(BO₂)₃ and PrCl(BO₂)₂: Two Praseodymium meta‐Borates in Comparison Single‐crystalline PrCl(BO₂)₂ can be obtained by the reaction of praseodymium, Pr₆O₁₁ and PrCl₃ with a small excess of B₂O₃ in evacuated silica tubes after seven days at 850 °C. If NaCl is additionally used as flux, single crystals of Pr(BO₂)₃ dominate the main product. Both praseodymium(III) meta‐borates are air and water stable. The crystals of PrCl(BO₂)₂ emerge as long, thin, pale green needles which tend to severe twinning due to their fibrous habit. The crystal structure (triclinic, P1¯; a = 420.56(4), b = 655.42(7), c = 808.34(8) pm, α = 82.361(8), β = 89.173(9), γ = 71.980(7)°, Z = 2) exhibits zigzag chains {[(B1)o^t_1/1O^e_2/2(B2)O^t_1/1O^e_2/2]²⁻} (≡ {[BO₂]⁻}) of corner‐linked [BO₃]³⁻ triangles with syndiotactic orientation of the terminal oxygen atoms which are running parallel to the [100] direction. The Pr³⁺ cations are surrounded by three Cl⁻ and seven O²⁻ anions with the shape of a tetracapped trigonal prism. The green, transparent crystals of Pr(BO₂)₃ (monoclinic, C2/c; a= 984.98(9), b = 809.57(8), c = 641.02(6) pm, β = 126.783(9)°, Z = 4) appear either lath‐shaped or rather spherical. In the crystal structure the B³⁺ cations reside both in trigonal planar as well as in tetrahedral coordination of oxygen atoms. Both types of borate polyhedra ([BO₃]³⁻ and [BO₄]⁵⁻) are linked via corners to form chains of the composition {[(B2)‐O^t_1/1O^e_2/2(B1)O^e_4/2(B2)O^t_1/1O^e_2/2]³⁻} (≡ {[BO₂]⁻}) which run parallel [101]. The coordination sphere of the Pr³⁺ cations consists of ten oxide anions which build up a bicapped square antiprism.     

Zwei Fluoridborate des Gadoliniums: Gd2F3[BO3] und Gd3F3[BO3]2

Two Fluoride Borates of Gadolinium: Gd₂F₃[BO₃] and Gd₃F₃[BO₃]₂ By flux‐supported solid‐state reaction of Gd₂O₃ and GdF₃ with B₂O₃ (flux: CsCl, molar ratio: 1 : 1 : 1 : 6, sealed tantalum capsule, 700 °C, 7 d) the new gadolinium fluoride borate Gd₂F₃[BO₃] (monoclinic, P2₁/c; a = 1637.2(1), b = 624.78(4), c = 838.04(6) pm, β = 93.341(8)°; V_m = 64.418(6) cm³/mol, Z = 8) was obtained as colourless, prismatic, face‐rich single crystals. The four crystallographically different Gd³⁺ cations (CN = 9) are all capped square‐antiprismatically surrounded by fluoride and oxide anions, in which the latter represent always components of isolated trigonal planar [BO₃]^3— anions. The six crystallographically independent F^— anions all reside in more or less planar coordination of three Gd³⁺ cations. Thus the constitution of Gd₂F₃[BO₃] can be described as a sequence of alternating layers each of the composition Gd[BO₃] and GdF₃ parallel (100), respectively. The crystal structures of Gd₂F₃[BO₃] and the shortly published Gd₃F₃[BO₃]₂ (monoclinic, C2/c; a = 1253.4(1), b = 623.7(1), c = 836.0(1) pm, β = 97.404(6)°; V_m = 97.571(9) cm³/mol, Z = 4) are compared with each other. Due to the structural analogies between these two gadolinium fluoride borates, a disorder model of the boron atoms frequently found for Gd₂F₃[BO₃] is able to be transferred to Gd₃F₃[BO₃]₂ as well.