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.     

Study on the kinetics of isothermal decomposition of selenites from IVB group of the periodic system

The thermal stability and kinetics of isothermal decomposition of the selenites of germanium, tin and lead was studied. A dependence between the process activation energy and the radius and electron polarizability of the cations was observed. It was explained with the different degree of the effect of counterpolarization of the selenite anion. The negative value of the change of entropy of activation showed that the active complex is more complicated formation than the reagent. The higher absolute value of the change of entropy measured for the formation of the active complex Ge(SeO₃)₂ compared to that for Sn(SeO₃)₂ shows that the degree of rearrangement (necessary changes) of the initial crystalline structure increases with the decrease of cation radius. The isothermal decomposition of the selenites from IVB group of the periodic system was considered to be ‘slow’ reaction due to the significantly lower than unity values of the steric factor.     

Pr4(SeO3)2(SeO4)F6 und NaSm(SeO3)(SeO4): Selenit‐Selenate der Selten‐Erd‐Elemente

Pr₄(SeO₃)₂(SeO₄)F₆ and NaSm(SeO₃)(SeO₄): Selenite‐Selenates of Rare Earth Elements Light green single crystals of Pr₄(SeO₃)₂(SeO₄)F₆ have been obtained from the decomposition of Pr₂(SeO₄)₃ in the presence of LiF in a gold ampoule. The monoclinic compound (C2/c, Z = 4, a = 2230.5(3), b = 710.54(9), c = 835.6(1) pm, β = 98.05(2)°, R_all = 0.0341) contains two crystallographically different Pr³⁺ ions. Pr(1)³⁺ is attached by six fluoride ions and two chelating SeO₃^2– groups (CN = 10), Pr(2)³⁺ is surrounded by four fluoride ions, three monodentate SeO₃^2– and two SeO₄^2– groups. One of the latter acts as a chelating ligand, so the CN of Pr(2)³⁺ is 10. The selenite ions are themselves coordinated by five and the selenate ions by four Pr³⁺ ions. The coordination number of the F^– ions is three and four, respectively. The linkage of the coordination polyhedra leads to cavities in the crystal structure which incorporate the lone pairs of the selenite ions. The reaction of Sm₂(SeO₄)₃ and NaCl in gold ampoules yielded light yellow single crystals of NaSm(SeO₃)(SeO₄). The monoclinic compound (P2₁/c, Z = 4, a = 1066.9(2), b = 691.66(8), c = 825.88(9) pm, β = 91.00(2)°, R_all = 0.0530) contains tenfold oxygen coordinated Sm³⁺ ions. The oxygen atoms belong to five SeO₃^2– and two SeO₄^2– ions. Two of the SeO₃^2– groups as well as one of the SeO₄^2– groups act as a chelating ligand. The sodium ions are surrounded by five SeO₄^2– ions and one SeO₃^2– group. One of the selenate ions is attached chelating leading to a coordination number of seven. Each selenite group is coordinated by six (5 × Sm³⁺ and 1 × Na⁺), each selenate ion by seven cations (5 × Na⁺ and 2 × Sm³⁺).     

High-Pressure Synthesis of SeCu 1− x Zn x O 3 Perovskites

The SeCu 1 m x Zn x O 3 solid solution, with a distorted perovskite-type structure, has been synthesized under high pressures and temperatures. X-ray diffraction analysis indicates that the zinc ions occupy the copper sites, a solid solution being formed. It seems that high-pressure stabilises a small cation such as Se 4+ in the A site of the perovskite structure ABO 3 although the material is better described as formed by selenite anions \rm{SeO}_{3}^{-} and Cu 2+ /Zn 2+ cations.     

Chemical vapor transport and solid-state exchange synthesis of new copper selenite bromides

A new dimorphic copper selenite bromide, Cu₅(SeO₃)₄Br₂ was obtained via chemical transport reactions. α-Cu₅(SeO₃)₄Br₂, monoclinic (1m) and β-Cu₅(SeO₃)₄Br₂, triclinic (1a) polymorphs were produced simultaneously upon reaction of amorphous, partially dehydrated copper selenite and copper bromide. 1m is similar to Cu₅(SeO₃)₄Cl₂, whereas 1a is distantly related to Ni₅(SeO₃)₄Br₂ and Co₅(SeO₃)₄Br₂. Attempts to reproduce synthesis of 1a via exchange reaction between Na₂SeO₃ and CuBr₂ resulted in a new Na₂[Cu₇O₂](SeO₃)₄Br₄ (2). Current study demonstrates for the first time, that both chemical vapor and exchange reactions can be employed in preparation of new selenite halides.     

Synthesis of rare-earth selenate and selenite materials under “sol-gel” hydrothermal conditions: crystal structures and characterizations of La(HSeO3)(SeO4) and KNd(SeO4)2

Two rare-earth compounds containing selenium atoms, La(HSeO₃)(SeO₄) with a new open framework structure and KNd(SeO₄)₂ with a layered structure, have been synthesized under “sol-gel” hydrothermal conditions for the first time. Single-crystals of La(HSeO₃)(SeO₄) crystallize in the monoclinic system (P2₁, , , , β=104.91(3)°, Z=2, R_All=0.032). The structure contains puckered polyhedral layers made of LaO_x (x=9,10) and SeO₄ groups, which are connected via SeO₃-uints to the 3D structure. The crytal structure of KNd(SeO₄)₂ (monoclinc, P2₁/c, , , , β=91.38(3)°, Z=4, R_All=0.051) contains honeycomb-like six-ring NdO₉ polyhedra forming layers which are further decorated with SeO₄ tetrahedra. The K⁺ ions occupy the interspaces of these layers and provide the charge balance.     

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.     

Zur Polymorphie und Pseudosymmetrie der Hydrate MSeO3 · H2O (M = Mn,Co, Ni,Zn, Cd)

Polymorphic and Pseudosymmetrical Hydrates MSeO₃ · H₂O (M = Mn, Co, Ni, Zn, Cd) By crystallization from aqueous solutions of MSeO₃ and M(HSeO₃)₂, the selenites MSeO₃ · H₂O (M = Mn, Co, Ni, Zn, Cd) were obtained and characterized by means of X-ray diffraction and IR-spectroscopy. The crystal structure of ZnSeO₃ · H₂O was determined. The IR spectra indicate that the hydrates are isotypic and contain H₂O molecules of symmetry mm2. However, the X-ray data show different structure types with H₂O molecules of site symmetry m or 1. CdSeO₃ · H₂O and MnSeO₃ · H₂O are isotypic (o.rh., MnSeO₃ · D₂O type). CoSeO₃ · H₂O (mon.) as well as the isotypic NiSeO₃ · H₂O and ZnSeO₃ · H₂O (mon.) form new structure types. These findings are discussed on the basis of the crystal structure of ZnSeO₃ · H₂O (P2₁/n, a = 477.9(1), b = 1319.4(5), c = 570.1(1) pm, β = 90.84(2)°, Z = 4, D_x = 3.886 g · cm^?3, R = 0.035 for 722 reflections with I > 2σ₁) and the local pseudosymmetry of its components, i.e., layers [ZnSeO₃ · H₂O] of ZnO₆ octahedra sharing four equatorial vertices, SeO₃^2? anions and H₂O molecules.     

Darstellung,Kristallstruktur und IR‐Spektren von BeSeO3 · H2O – Wasserstoffbrücken und Korrelation von IR‐ und Strukturdaten in den Monohydraten MSeO3 · H2O (M = Be,Ca, Mn,Co, Ni,Zn, Cd)

Preparation, Crystal Structure and IR Spectra of BeSeO₃ · H₂O – Hydrogen Bonds and Correlation of IR and Structure Data in the Monohydrates MSeO₃ · H₂O (M = Be, Ca, Mn, Co, Ni, Zn, Cd) BeSeO₃ · H₂O (oP32) has been obtained by treating amorphous BeSeO₃ · 4 H₂O precipitated from Be(HSeO₃)₂ solutions hydrothermally at 150 °C. The crystal structure (P2₁2₁2₁, a = 560.59(4), b = 755.25(5), c = 781.14(5) pm, Z = 4, D_X = 3.092 gcm^–3, R = 0.018 for the 2034 reflections with I > 2σ_I of the enantiomer investigated) contains BeO₃(H₂O) tetrahedra built up from three selenite and one water oxygen atoms. The BeO₃(H₂O) tetrahedra are 3 D‐connected via Se atoms of trigonal pyramidal SeO₃^2– ions. The Be–O distances are 161.8 to 164.4 pm. The Se–O bond lenghts (169.2–170.3 pm) and the O–Se–O bond angles (98.1–101.4°) are normal. The water molecules of crystallization form together with the SeO₃^2– ions screw‐like hydrogen bond systems along [100]. Despite the strong synergetic effect of the Be²⁺ ions, the hydrogen bonds (d(OH…O) = 267.4 and 276.4 pm, respectively; ν_OD of matrix isolated HDO molecules: 2244 and 2405 cm^–1, respectively) are normal compared to other neutral selenite hydrates. Together with the hitherto known monohydrates M^IISeO₃ · H₂O and other beryllium salt hydrates, the hydrogen bonds of BeSeO₃ · H₂O are discussed with regard to their geometry and IR spectroscopy.     

Two new octahedral/pyramidal frameworks containing both cation channels and lone-pair channels: syntheses and structures of Ba2MnMn2(SeO3)6 and PbFe2(SeO3)4

The hydrothermal syntheses, single crystal structures, and some properties of Ba₂Mn^IIMn₂^III(SeO₃)₆ and PbFe₂(SeO₃)₄ are reported. These related phases contain three-dimensional frameworks of vertex (FeO₆) and vertex/edge linked (MnO₆) octahedra and SeO₃ pyramids. In each case, the MO₆/SeO₃ framework encloses two types of 8 ring channels, one of which encapsulates the extra-framework cations and one of which provides space for the Se^IV lone pairs. Crystal data: Ba₂Mn₃(SeO₃)₆, M_r=1201.22, monoclinic, P2₁/c (No. 14), a=5.4717 (3) Å, b=9.0636 (4) Å, c=17.6586 (9) Å, β=94.519 (1)°, V=873.03 (8) Å³, Z=2, R(F)=0.031, wR(F²)=0.070; PbFe₂(SeO₃)₄, M_r=826.73, triclinic, (No. 2), a=5.2318 (5) Å, b=6.7925 (6) Å, c=7.6445 (7) Å, α=94.300 (2)°, β=90.613 (2)°, γ=95.224 (2)°, V=269.73 (4) Å³, Z=1, R(F)=0.051, wR(F²)=0.131.