CoSm(SeO3)2Cl,CuGd(SeO3)2Cl,MnSm(SeO3)2Cl,CuGd2(SeO3)4 und CuSm2(SeO3)4: Übergangsmetallhaltige Selenite von Samarium und Gadolinum

CoSm(SeO₃)₂Cl, CuGd(SeO₃)₂Cl, MnSm(SeO₃)₂Cl, CuGd₂(SeO₃)₄ and CuSm₂(SeO₃)₄: Transition Metal containing Selenites of Samarium and Gadolinum The reaction of CoCl₂, Sm₂O₃, and SeO₂ in evacuated silica ampoules lead to blue single crystals of CoSm(SeO₃)₂Cl (triclinic, , Z = 4, a = 712.3(1), b = 889.5(2), c = 1216.2(2) pm, α = 72.25(1)°, β = 71.27(1)°, γ = 72.08(1)°, R_all = 0.0586). If MnCl₂ is used in the reaction light pink single crystals of MnSm(SeO₃)₂Cl (triclinic, , Z = 2, a = 700.8(2), b = 724.1(2), c = 803.4(2) pm, α = 86.90(3)°, β = 71.57(3)°, γ = 64.33(3)°, R_all = 0.0875) are obtained. Green single crystals of CuGd₂(SeO₃)₂Cl (triclinic, , Z = 4, a = 704.3(4), b = 909.6(4), c = 1201.0(7) pm, α = 70.84(4)°, β = 73.01(4)°, γ = 70.69(4)°, R_all = 0.0450) form analogously in the reaction of CuCl₂ and Gd₂O₃ with SeO₂. CoSm(SeO₃)₂Cl contains [CoO₄Cl₂] octahedra, which are connected via one edge and one vertex to infinite chains. The Mn²⁺ ions in MnSm(SeO₃)₂Cl are also octahedrally coordinated by four oxygen and two chlorine ligands. The linkage of the polyhedra to chains occurs exclusively via edges. Both, the cobalt and the manganese compound show the Sm³⁺ ions in eight and ninefold coordination of oxygen atoms and chloride ions. In CuGd(SeO₃)₂Cl the Cu²⁺ ions are coordinated by three oxygen atoms and one Cl^— ion in a distorted square planar manner. One further Cl^— and one further oxygen ligand complete the [CuO₃Cl] units yielding significantly elongated octahedra. The latter are again connected to chains via two common edges. For the Gd³⁺ ions coordination numbers of ?8 + 1”? and nine were found. Single crystals of the deep blue selenites CuM₂(SeO₃)₄ (M = Sm/Gd, monoclinic, P2₁/c, a = 1050.4(3)/1051.0(2), b = 696.6(2)/693.5(1), c = 822.5(2)/818.5(2) pm, β = 110.48(2)°/110.53(2)°, R_all = 0.0341/0.0531) can be obtained from reactions of the oxides Sm₂O₃ and Gd₂O₃, respectively, with CuO and SeO₂. The crystal structure contains square planar [CuO₄] groups and irregular [MO₉] polyhedra.     

Nd2(SeO3)2(SeO4) · 2H2O – a Mixed‐Valence Compound containing Selenium in the Oxidation States +IV and +VI

Pale pink crystals of Nd₂(SeO₃)₂(SeO₄) · 2H₂O were synthesized under hydrothermal conditions from H₂SeO₃ and Nd₂O₃ at about 200 °C. X‐ray diffraction on powder and single‐crystals revealed that the compound crystallizes with the monoclinic space group C 2/c (a = 12.276(1) Å, b = 7.0783(5) Å, c = 13.329(1) Å, β = 104.276(7)°). The crystal structure of Nd₂(SeO₃)₂(SeO₄) · 2H₂O is an ordered variant of the corresponding erbium compound. Eight oxygen atoms coordinate the Nd^III atom in the shape of a bi‐capped trigonal prism. The oxygen atoms are part of pyramidal (Se^IVO₃)^2? groups, (Se^VIO₄)^2? tetrahedra and water molecules. The [NdO₈] polyhedra share edges to form chains oriented along [010]. The selenate ions link these chains into layers parallel to (001). The layers are interconnected by the selenite ions into a three‐dimensional framework. The dehydration of Nd₂(SeO₃)₂(SeO₄) · 2H₂O starts at 260 °C. The thermal decomposition into Nd₂SeO₅, SeO₂ and O₂ at 680 °C is followed by further loss of SeO₂ leaving cubic Nd₂O₃.     

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.     

Ce2[SeO3]3 and Pr2[SeO3]3: Non‐Isostructural Oxoselenates(IV) of the Light Lanthanoids

The crystal structures of Ce₂[SeO₃]₃ and Pr₂[SeO₃]₃ have been refined from X‐ray single‐crystal diffraction data. The compounds were obtained using stoichiometric mixtures of CeO₂, SeO₂, Ce, and CeCl₃ (molar ratio 3:3:1:1) or Pr₆O₁₁, SeO₂, Pr, and PrCl₃ (molar ratio 3:27:1:2) heated in evacuated sealed silica tubes at 830 °C for one week. Ce₂[SeO₃]₃ crystallizes orthorhombically (space group: Pnma), with four formula units per unit cell of the dimensions a = 839.23(5) pm, b = 1421.12(9) pm, and c = 704.58(4) pm. Its structure contains only a single crystallographically unique Ce³⁺ cation in tenfold coordination with oxygen atoms arranged as single‐face bicapped square antiprism and two different trigonal pyramidal [SeO₃]^2? groups. The connectivity among the [CeO₁₀] polyhedra results in infinite sheets of face‐ and edge‐sharing units propagating normal to [001]. Pr₂[SeO₃]₃ is monoclinic (space group: P2₁/n) with twelve formula units per unit cell of the dimensions a = 1683.76(9) pm, b = 705.38(4) pm, c = 2167.19(12) pm, and β = 102.063(7)°. Its structure exhibits six crystallographically distinct Pr³⁺ cations in nine‐ and tenfold coordination with oxygen atoms forming distorted capped square antiprisms or prisms (CN = 9), bicapped square antiprisms and tetracapped trigonal prisms (CN = 10), respectively. The [PrO₉] and [PrO₁₀] polyhedra form double layers parallel to (111) by edge‐ or face‐sharing, which are linked by nine different [SeO₃]^2? groups to build up a three‐dimensional framework. In both compounds, the discrete [SeO₃]^2? anions (d(Se⁴⁺–O^2?) = 166–174 pm) show the typical Ψ¹‐tetrahedral shape owing to the non‐bonding “lone‐pair” electrons at the central selenium(IV) particles. Moreover, their stereochemical “lone‐pair” activity seems to flock together in large empty channels running along [010] in the orthorhombic Ce₂[SeO₃]₃ and along [101] in the monoclinic Pr₂[SeO₃]₃ structure, respectively.     

Gd3(SeO3)4F: Ein Fluoridselenit mit μ3‐SeO32–und μ3‐F–‐überkappten Gd3‐Ringen

Gd₃(SeO₃)₄F: A Fluoride Selenite with μ₃‐SeO₃^2– and μ₃‐F^– Capped Gd₃ Rings The decomposition of Gd₂(SeO₄)₃ in the presence of LiF in sealed gold ampoules yields single crystals of Gd₃(SeO₃)₄F (hexagonal, P6₃mc, Z = 2, a = 1044.3(1), b = 694.32(7) pm, R_all = 0.0286). In the crystal structure one SeO₃^2– group and one F^– ion cap a ring of three Gd atoms. Furthermore, the crystal structure is strongly influenced by the lone pairs of the SeO₃^2– ions.     

Ag9I3(SeO4)2(IO3)2 – Synthesis,Crystal Structure,and Ionic Conductivity

Ag₉I₃(SeO₄)₂(IO₃)₂ was obtained for the first time by reacting a stoichiometric mixture of Ag₂O, AgI and SeO₂ at elevated oxygen pressure (255 MPa) and at a temperature of 500 °C. Ag₉I₃(SeO₄)₂(IO₃)₂ was characterized by X‐ray powder diffraction, differential scanning calorimetry, impedance spectroscopy and single crystal structure analysis. The crystal structure was solved by direct methods (I23, Z = 8, a = 12.9584(6) Å, V = 2175.9(2) ų and R₁ = 2.70 %). The crystal structure consists of isolated SeO₄ tetrahedra and trigonal IO₃ pyramids separated by Ag⁺ and I^– ions. Each four of the SeO₄^2– and IO₃^– anions aggregate, forming a novel supramolecular building block, showing a hetero‐cubane like structure. According to the results of impedance measurements, Ag₉I₃(SeO₄)₂(IO₃)₂ is a good silver ion conductor. The compound shows an abrupt increase in the ionic conductivity in the temperature range of 115 to 147 °C, and has a silver ion conductivity of 7.1 × 10^–5 Ω^–1 cm^–1 at 25 °C. The activation energy for silver ion conduction is 0.45 eV, in the temperature range from 25 to 115°.     

RbAu(SeO4)2: First Structure Determination of a Ternary Gold Selenate

Yellow single crystals of RbAu(SeO₄)₂ were obtained upon evaporation of a solution prepared from the reaction of elemental gold and Rb₂CO₃ with conc. selenic acid. In the crystal structure (monoclinic, C2/m, Z = 2, a = 1078.7(4), b = 522.7(1), c = 739.3(2) pm, β = 116.45(2)°) Au³⁺ is in square planar coordination of oxygen atoms which belong to four SeO₄^2- ions. According to [Au(SeO₄)_4/2]^- anionic chains are formed which are connected by the Rb⁺ ions. The latter are surrounded by two chelating and six monodentate selenate groups leading to a CN of 10.     

Wasserfreie Selenite des Lanthans: Synthese und Kristallstruktur von La2(SeO3)3 und LaFSeO3

Anhydrous Selenites of Lanthanum: Syntheses and Crystal Structures of La₂(SeO₃)₃ and LaFSeO₃ Colorless single crystals of La₂(SeO₃)₃ were obtained via the decomposition of La₂(SeO₄)₃ in the presence of NaCl in sealed gold ampoules. The compound crystallizes in the orthorhombic system (Pnma, Z = 4, a = 846.7(1), b = 1428.6(1), c = 710.3(2) pm, R_all = 0.0223) and contains La³⁺ in tenfold coordination of oxygen atoms which belong to seven SeO₃^2– groups. Hence, three of the latter act as bidentate ligands. The reaction of LiF with La₂(SeO₄)₃ in sealed gold ampoules yielded colorless single crystals of LaFSeO₃ (monoclinic, P2₁/c, Z = 12, a = 1819.8(3), b = 715.75(8), c = 846.4(1) pm, β = 96.89(2)°, R_all = 0.0352). The crystal structure contains three crystallographically different La³⁺ ions. La1 is surrounded by six oxygen atoms from five SeO₃^2– groups and four fluoride ions, La2 is coordinated by two bidentate SeO₃^2– ions and seven fluoride ligands. La3 is surrounded by oxygen atoms only with the coordination number and polyhedron being almost the same as found for La³⁺ in La₂(SeO₃)₃. Furthermore, the crystal structures of both compounds are strongly influenced by the lone pairs of the SeO₃^2– groups.     

Pr5F[SiO4]2[SeO3]3: Another Complex Fluoride Oxosilicate Oxoselenate(IV)

During attempts to synthesize lanthanoid(III) fluoride oxoselenates(IV) with the simple composition MF[SeO₃], not only Pr₃F[SeO₃]₄, but also Pr₅F[SiO₄]₂[SeO₃]₃ appeared as pale green crystalline by‐products in the case of praseodymium. Pr₅F[SiO₄]₂[SeO₃]₃ crystallizes triclinically in space group P$\bar{1}$ (no. 2) with a = 701.14(5), b = 982.68(7), c = 1286.79(9) pm, α = 70.552(3), β = 76.904(3), γ = 69.417(3)° and Z = 2. The five crystallographically different Pr³⁺ cations on the general positions 2i show coordination numbers of eight and nine. [(Pr1)O₈]^13– and [(Pr2)O₈]^13– polyhedra are connected to$\bar{1}$ {[(Pr1, 2)₂O₁₂]^18–} chains along the [100] direction. [(Pr3)O₇F]^12–, [(Pr4)O₈F]^14– and [(Pr4)O₈F]^14– polyhedra generate [F(Pr3, 4, 5)₃O₁₉]^30– units about their central F^– anion in triangular Pr³⁺ coordination. These units form $\bar{1}$ {[F(Pr3, 4, 5)₃O₁₆]^24–} strands, again running parallel to [100]. Their alternating connection with the $\bar{1}$ {[(Pr1, 2)₂O₁₂]^18–} chains results in $\bar{1}$ {[Pr₅O₂₀F]^26–} sheets parallel to the (001) plane. Like in the already known related compound Er₃F[SiO₄][SeO₃]₂, a three‐dimensional network $\bar{1}$ {[Pr₅O₁₇F]^20–} is achieved without the contribution of both the tetravalent silicon and selenium components. However, two Si⁴⁺ and three Se⁴⁺ cations forming tetrahedral [SiO₄]^4– and ψ¹‐tetrahedral [SeO₃]^2– units with all O^2– anions guarantee the charge balance. The formation of Pr₅F[SiO₄]₂[SeO₃]₃ was observed when praseodymium sesquioxide (Pr₂O₃: in‐situ produced from Pr and Pr₆O₁₁ in a molar ratio of ³/₁₁:⁴/₁₁),praseodymium trifluoride (PrF₃) and selenium dioxide (SeO₂) in 1:1:3 molar ratios were reacted with CsBr as fluxing agent for five days at 750 °C in evacuated fused silica (SiO₂) ampoules.     

Synthese und Kristallstruktur von NaPr2F3(SO4)2

Synthesis and Crystal Strucure of NaPr₂F₃(SO₄)₂ Light green single crystals of NaPr₂F₃(SO₄)₂ have been obtained by the reaction of Pr₂(SO₄)₃ and NaF in sealed gold ampoules at 1050 °C. In the crystal structure (monoclinic, I2/a, Z = 4, a = 822.3(1), b = 692.12(7), c = 1419.9(2) pm, β = 95.88(2)°) Pr³⁺ is coordinated by four F^– ions and six oxygen atoms which belong to five SO₄^– ions. Thus, one of the latter acts as a bidentate ligand. The [PrO₆F₄] units are connected via three common fluoride ions to pairs with a Pr–Pr distance of 386 pm. Na⁺ is sevenfold coordinated by three fluorine and four oxygen atoms.     

Hydrogenselenate der Selten‐Erd‐Elemente: Synthese und Kristallstruktur von La(HSeO4)3 und Gd(HSeO4)(SeO4)

Hydrogenselenates of Rare Earth Elements: Syntheses and Crystal Structures of La(HSeO₄)₃ and Gd(HSeO₄)(SeO₄) Colorless transparent single crystals of La(HSeO₄)₃ (hexagonal, P6₃/m, Z = 2, a = 971.7(1), c = 616.98(8) pm, R_all = 0.0440) were obtained from the reaction of La₂O₃ and conc. selenic acid. La(HSeO₄)₃ is isotypic with the corresponding hydrogensulfate. Its structure can be seen as a variant of the UCl₃ type structure with complex anions and contains the La³⁺ ions in ninefold coordination of oxygen atoms. Single crystals of Gd(HSeO₄)(SeO₄) crystallize from a solution of Gd₂O₃ in selenic acid (70% H₂SeO₄). In the orthorhombic crystal structure (Pbca, Z = 8, a = 920.4(1), b = 1351.6(2), c = 1004.0(1) pm, R_all = 0.0276) the Gd³⁺ ions are coordinated by eight oxygen atoms belonging to four SeO₄^2– and four HSeO₄^– ions. These are surrounded by four Gd³⁺ ions.     

Sm2Se5O13: A Selenite–Diselenite according to Sm2(SeO3)(Se2O5)2

Pale yellow single crystals of Sm₂(SeO₃)(Se₂O₅)₂ (monoclinic, P2₁/c, Z = 4, a = 1003.6(2), b = 1022.5(2), c = 1287.3(2) pm, β = 112.3(2)°) were obtained from the reaction of Sm₂O₃ and SeO₂ at 350 °C in a sealed glass ampoule. In the crystal structure both Se₂O₅^2? and SeO₃^2? groups connect the Sm³⁺ ions into layers. Between the layers the lone electron pairs of the anions are located.     

Synthesis and Crystal Structures of α‐ and β‐Mg2[(UO2)3(SeO4)5](H2O)16

Single crystals of α‐ and β‐Mg₂[(UO₂)₃(SeO₄)₅](H₂O)₁₆ have been synthesized by evaporation from an aqueous solution of the ionic components. The structure of α‐Mg₂[(UO₂)₃(SeO₄)₅](H₂O)₁₆ (monoclinic, C2/c, a = 19.544(3), b = 10.4783(11), c = 18.020(3) Å, β = 91.352(12)°, V = 3689.3(9) ų) has been solved by direct methods and refined to R₁ = 0.048 on the basis of 4338 unique observed reflections. The structure of β‐Mg₂[(UO₂)₃(SeO₄)₅](H₂O)₁₆ (orthorhombic, Pbcm, a = 10.3807(7), b = 22.2341(19), c = 33.739(5) Å, V = 7787.2(14) ų) has been solved by direct methods and refined to R₁ = 0.107 on the basis of 3621 unique observed reflections. The structures of α‐ and β‐Mg₂[(UO₂)₃(SeO₄)₅](H₂O)₁₆ are based upon sheets with the chemical composition [(UO₂)₃(SeO₄)₅]^4‐. The sheets are formed by corner sharing between pentagonal bipyramids [UO₇]^8‐ and SeO₄^2‐ tetrahedra. In the α‐modification, the [(UO₂)₃(SeO₄)₅]^4‐ sheets are more or less planar and run parallel to (001). In the structure of the β‐modification, the uranyl selenate sheets are strongly corrugated and oriented parallel to (010). The [Mg(H₂O)₆]²⁺ polyhedra reside in the interlayers and provide three‐dimensional linkage of the uranyl selenate sheets via hydrogen bonding. In addition to H₂O groups attached to Mg²⁺ cations, both structures also contain H₂O molecules that are not bonded to any cation. The [(UO₂)₃(SeO₄)₅]^4‐ sheets in the structures of α‐ and β‐Mg₂[(UO₂)₃(SeO₄)₅](H₂O)₁₆ represent two different structural isomers. The sequences of the orientations of the tetrahedra within the sheets can be described by their orientational matrices with their shortened forms ( ddudd □ /uu □ uud ) and ( dd □ dd □ uu □ uu □ /uuduumdduddm ) for α‐ and β‐Mg₂[(UO₂)₃(SeO₄)₅](H₂O)₁₆, respectively. A short review on the isomerism of [(UO₂)₃(TO₄)₅]^4‐ sheets (T = S, Cr, Se, Mo) is given.     

The Unique Crystal Structure of the Triclinic Samarium(III) Oxoselenate(IV) Sm2[SeO3]3

Pale yellow, needle‐shaped single crystals of Sm₂[SeO₃]₃ were obtained by heating stoichiometric mixtures of Sm₂O₃ and SeO₂ (molar ratio: 1:3) along with substantial amounts of CsCl as fluxing agent in evacuated sealed silica tubes at 830 °C for one week. According to X‐ray single‐crystal diffraction data, Sm₂[SeO₃]₃ crystallizes triclinic (space group: ) with two formula units per unit cell of the dimensions a = 698.62(7), b = 789.71(8), c = 910.34(9) pm, α = 96.693(5), β = 104.639(5), γ = 115.867(5)°. Its crystal structure contains two crystallographically distinct Sm³⁺ cations in eight‐ and ninefold coordination with oxygen atoms arranged as distorted uncapped or capped square antiprisms (d(Sm³⁺?O^2?) = 232?271 pm). These [(Sm1)O₈] and [(Sm2)O₉] polyhedra share opposite edges and faces to form zigzag chains along [100] with discrete pyramidal [SeO₃]^2? anions bridging units. Further linkage by [SeO₃]^2? anions in [010] direction leads to a three‐dimensional network, which exhibits almost rectangular channels along [111]. These tunnels offer width enough to incorporate the free non‐bonding electron pairs (?lone pairs”?) at the Se⁴⁺ cations, since all nine different Ψ¹‐tetrahedral [SeO₃]^2? groups (d(Se⁴⁺?O^2?) = 165?173 pm, ?(O–Se–O) = 94 – 108°) exhibit a pronounced stereochemical ?lone‐pair”? activity. For not being isotypic with neither triclinic Er₂[SeO₃]₃ (CN(Er³⁺) = 7 and 8) nor the remainder rare‐earth metal(III) oxoselenates(IV) of the composition M₂[SeO₃]₃ (≡ M₂Se₃O₉; M = Sc, Y, La, Ce – Lu), Sm₂[SeO₃]₃ claims a unique crystal structure among them.     

Das erste Hexaoxoselenat (VI) – Synthese und Charakterisierung von Na12(SeO6)(SeO4)3

The First Hexaoxoselenate(VI) – Synthesis and Characterization of Na₁₂(SeO₆)(SeO₄)₃ Pure Na₁₂(SeO₆)(SeO₄)₃ has been prepared by solid state reaction at 500 °C from a mixture of Na₂O and Na₂SeO₄ in silver crucibles. The crystal structure has been determined from single crystal data (Pnma, a = 1577.2(7), b = 781.7(3), c = 1475.5(7) pm, Z = 4, R1 = 0.030, wR2 = 0.058, 2480 observed reflections [I_o ≥ 2σ(I_o)]). Na₁₂(SeO₆)(SeO₄)₃ contains novel SeO₆^6– anions. There exists an unexpected topological relationship between the SeO₆Naⁱ₈Na^a₂Na^a_4/2 part of the structure and the MoCl₂ structure type (Mo₆Clⁱ₈Cl^a₂Cl^a_4/2). The crystal structure as determined is consistent with spectroscopic data (IR, Raman, ⁷⁷Se‐MAS‐NMR).     

Synthesis,Crystal Structures,and Optical Properties of AM2(OH)(SeO3)2 (A = Na,Rb; M = Mg,Zn)

Sodium magnesium selenite NaMg₂(OH)(SeO₃)₂ and rubidium zinc selenite RbZn₂(OH)(SeO₃)₂ were prepared by hydrothermal reactions. The crystal structures of the title compounds were determined by single‐crystal X‐ray diffraction. NaMg₂(OH)(SeO₃)₂ crystallizes in the orthorhombic space group Pnma (no. 62) with lattice parameters a = 13.1919(10), b = 6.0415(4), c = 8.2182(6) Å, and Z = 4 and RbZn₂(OH)(SeO₃)₂ crystallizes in the triclinic space group P$\bar{1}$ (no. 2) with lattice parameters a = 4.8698(5), b = 7.3446(8), c = 11.7796(12) Å, α = 82.554(3), β = 78.456(2), γ = 71.603(3)°,and Z = 2. The structure of NaMg₂(OH)(SeO₃)₂ is a three‐dimensional framework consisting of edge‐sharing MgO₆ octahedra and trigonal pyramidal SeO₃^2– groups, whereas the structure of RbZn₂(OH)(SeO₃)₂ is a two‐dimensional layers structure consisting of corner‐sharing [Zn₂O₇] dimers linked by trigonal pyramidal SeO₃^2– groups. The compounds were characterized by the solid state UV/Vis/NIR diffuse reflectance, and FT‐IR spectroscopy.     

Einfach und doppelt deprotonierte Maleinsäure in Praseodym‐hydrogenmaleat‐octahydrat,Pr(C4O4H3)3 · 8 H2O,und Praseodym‐maleatchlorid‐tetrahydrat,Pr(C4O4H2)Cl · 4 H2O

Single and Double Deprotonated Maleic Acid in Praseodymium Hydrogenmaleate Octahydrate, Pr(C₄O₄H₃)₃ · 8 H₂O, and Praseodymiummaleatechloride Tetrahydrate, Pr(C₄O₄H₂)Cl · 4 H₂O Single crystals of Pr(C₄O₄H₃)₃ · 8 H₂O grew by slow evaporation of a solution which had been obtained by dissolving Pr(OH)₃ in aqueous maleic acid. The triclinic compound (P1, Z = 2, a = 728.63(3), b = 1040.23(3), c = 1676.05(8) pm, α = 72.108(2)°, β = 87.774(2)°, γ = 70.851(2)°, R_all = 0.0261) contains Pr³⁺ ions in ninefold coordination of oxygen atoms which belong to two monodentate maleate ions and seven H₂O molecules. There is one further non‐coordinating maleate ion and one crystal water molecule in the unit cell. Thermal treatment of Pr(C₄O₄H₃)₃ · 8 H₂O leads first to the anhydrous compound which then decomposes to the respective oxide in two steps upon further heating. Evaporation of a solution of Pr(C₄O₄H₃)₃ · 8 H₂O which contained additional Cl^– ions yielded single crystals of Pr(C₄O₄H₂)Cl · 4 H₂O. In the crystal structure (monoclinic, P2₁/c, Z = 4, a = 866.0(1), b = 1344.3(1), c = 896.9(1) pm, β = 94.48(2)°, R_all = 0.0227), the Pr³⁺ ions are surrounded by nine oxygen atoms. The latter belong to four H₂O molecules and three maleate ions. Two of the latter act as bidentate ligands.     

(NH4)4Cd(HSeIVO3)2(SeVIO4)2: a new structure type with kröhnkite‐like chains

Tetra­ammonium cadmium di­hydrogenselenite(IV) diselen­ate(VI), (NH₄)₄Cd(HSe^IVO₃)₂(Se^VIO₄)₂, is the third example of a compound containing both hydrogen selenite and selenate anions, and has a new structure type. It contains kröhnkite‐like heteropolyhedral chains in which CdO₆ octahedra are linked via bridging HSeO₃ groups, having their remaining two trans apices decorated by SeO₄ groups. The charge‐balancing NH₄ groups are involved in weak hydrogen bonding, whereas the H atom of the HSeO₃ group provides a strong hydrogen bond [O⋯O = 2.614 (5) Å]. The average Cd—O bond length is 2.298 Å. All atoms are on general positions except Cd (on ). Relations to the kröhnkite‐type compounds Na₂Mg(SO₃)·2H₂O, Ba₂CoCl₂(SeO₃)₂ and Ba₂Ca(HPO₄)₂(H₂PO₄)₂, and to the mineral curetonite are dis­cussed. Unit‐cell data are given for an isotypic Mn^II analogue.     

Synthese,Struktur und Thermolyse der ternären Ammoniumnitrate (NH4)3[M2(NO3)(9] (M  La?Gd)

Synthesis, Structure, and Thermolysis of the (NH₄)₃[M₂(NO₃)₉] (M ? La? Gd) The ternary ammonium nitrates (NH₄)₃[M₂(NO₃)₉] (M ? La-Gd) are obtained as single crystals from a solution of the respective sesquioxides in a melt of NH₄NO₃ and sublimation of the excess NH₄NO₃. In the crystal structure of (NH₄)₃[Pr₂(NO₃)₉] (cubic, P4₃32, Z = 4, a = 1 377.0(1) pm, R = 0.038, R_w = 0.023) Pr³⁺ is surrounded by six bidentate nitrate ligands of which three are bridging to neighbouring Pr³⁺ ions. This results in a branched folded chain, held together by the NH₄⁺ ions which occupy cavities in the structure. (NH₄)₃[Pr₂(NO₃)₉] is the first intermediate product of the thermal decomposition of (NH₄)₂[Pr(NO₃)₅(H₂O)₂] · 2H₂O.