Refinement of the crystal structure of calcioancylite-(Ce) by the Rietveld method

The crystal structure of calcioancylite-(Ce) of the (Ca_0.30Sr_0.22)_Σ0.52(Ce_0.78La_0.47Nd_0.16Pr_0.05Sm_0.02)_Σ1.48(CO₃)₂((OH)_1.20F_0.28)_Σ1.48 · 1.97H₂O composition from alkali hydrothermalites of Mont Saint-Hilaire, Canada, has been refined by the Rietveld method. The refinement details are as follows: ADP-2 diffractometer, λCuK _α radiation, Ni filter, 10.50° < 2θ < 140.00°, and the number of reflections (α₁ + α₂) 652. All calculations have been performed within the sp. gr. Pmcn (a = 5.0095(1) Å, b = 8.5006(1) Å, c = 7.2670(1) Å, V = 309.46(1) ų, R _wp = 3.45) in the anisotropic approximation of thermal vibrations for cations.     

Determination of the crystal structure of khanneshite by the Rietveld method

The crystal structure of khanneshite (Na_2.75Ca_0.23)_2.98(Ba_1.08Sr_0.63Ca_0.46Ce_0.46La_0.18Nd_0.15Pr_0.04)_3.00 · (CO₃)₅ found in carbonatites from the Khibiny massif (the Kola Peninsula) was solved by the Rietveld method. The X-ray diffraction data were collected on a focusing STOE-STADIP diffractometer equipped with a bent Ge(111) primary-beam monochromator (λMoKα₁ radiation, 2.00° < 2θ < 54.98°, 311 reflections). All the calculations were performed within the sp. gr. P6₃ mc; a = 10.5790(1) Å, c = 6.5446(1) Å, V = 634.31(1) ų, R _P = 2.38, R _wp = 3.26, R _B = 1.42, R _F = 1.79. The atoms of the cations were refined with anisotropic thermal parameters.     

Refinement of the crystal structures of low-rare-earth and “typical” burbankites by the Rietveld method

The crystal structures of two samples of burbankite from the Khibiny massif, namely, low-rare-earth burbankite (Na_1.82Ca_1.02Y_0.02)_2.86(Sr_2.32Ba_0.43Ca_0.17La_0.06Ce_0.02)_3.00(CO₃)₅ from pectolite metasomatites and burbankite of the characteristic composition (Na_2.22Ca_0.65Y_0.03)_2.97 × × (Sr_2.10Ba_0.33Ce_0.23Ca_0.15La_0.12Nd_0.05Pr_0.02)_3.00(CO₃)₅ from alkaline hydrothermolites, were refined by the Rietveld method. The experimental data were collected on an ADP-2 diffractometer (λCuK _α radiation, Ni-filter; 15.00° < 2θ < 155.00°; 2θ scan with steps 0.02°; the exposure time per step, 15–20 s; the number of (α₁ + α₂) reflections 556–570). All the calculations were performed using the WYRIET program (version 3.3) in the sp. gr. P6₃ mc. For low-rare-earth burbankite: a = 10.5263(1) Å, c = 6.5392(1) Å, R _P = 3.52, R _wp = 4.49, R _B = 4.10, and R _F = 4.11. For burbankite from alkaline hydrothermolites: a = 10.5313(1) Å, c = 6.4829(1) Å, R _P = 2.54, R _wp = 3.23, R _B = 3.06, and R _F = 3.44. The structures were refined using the anisotropic thermal parameters of cations.     

Crystal structure of magnesioferrikatophorite

The crystal structure of the Na,Ca-amphibole magnesioferrikatophorite found in carbonatites from the Turiy Cape (Kola Peninsula) was refined (Siemens P4 diffractometer, λMoK _α radiation, 1481 independent reflections with |F|>4σ(F), anisotropic refinement, R(F) = 0.039). The parameters of the monoclinic unit cell are a = 9.875(5) Å, b = 18.010(8) Å, c = 5.309(3) Å, β = 104.39(5)°, sp. gr. C2/m, Z = 2. The distribution of the cations over the crystallographically nonequivalent M(1–4)-positions was revealed by Mössbauer spectroscopy and X-ray diffraction analysis. The character of splitting of the A-position correlates with the characteristic features of the magnesioferrikatophorite composition. The resulting structural formula (Na_0.87K_0.13)_{Σ = 1} · (Na_1.18Ca_0.82)_{Σ = 2}(Mg_1.41Fe _0.42 ³⁺ Ti _0.17 ⁴⁺ )_{Σ= 2} Fe _1.31 ³⁺ Mg_0.69)_{Σ = 2}(Mg_0.60Fe _0.38 ²⁺ Mn_0.02)_{Σ = 1}(Si_3.16Al_0.84)_{Σ = 4} · Si₄O₂₂(O_1.05OH_0.66F_0.29)_{Σ= 2} agrees well with the electron microprobe analysis data. Based on the zonal character of the crystal and high Fe ³⁺ content, the conditions of crystallogenesis are defined as oxidative against the background of a decrease in the Na potential in the course of the evolution of a mineral-forming system.     

Crystal structure of calcioburbankite and the characteristic features of the burbankite structure type

The crystal structure of calcioburbankite (Na,Ca)₃(Ca,RE,Sr,Ba)₃(CO₃)₅ found in carbonatites from Vuoriyarvi (North Kareliya) was solved by the Rietveld method. The experimental data were collected on an ADP-2 diffractometer (λCuK _α radiation; Ni filter; 16.00° < 2θ < 130.00°; the number of (α₁ + α₂) reflections was 455). All the calculations were performed within the sp. gr. P6₃ mc; a = 10.4974(1) Å, c = 6.4309(1) Å, V = 613.72(1) ų; R _wp = 2.49%. The structure was refined with the use of the anisotropic thermal parameters for the (Na,Ca) and (Sr,Ba,Ce) cations. The comparison of the crystal structures of all of the known hexagonal representatives of the burbankite family demonstrates that the burbankite structure type (sp. gr. P6₃ mc) is stable, irrespectively of the occupancy of the ten-vertex polyhedra predominantly with Ca, Sr, or Ba cations and the occupancies of the positions in the eight-vertex polyhedra.     

Crystal structures of double vanadates, Ca9 R(VO4)7 ⋅ III. R = Nd, Sm, Gd, or Ce

The crystal structures of Ca₉ R(VO₄)₇ (R = Nd (I), Sm (II), or Gd (III)) were studied by the Rietveld method. The compounds are isostructural to Ca₃(VO₄)₂ and are crystallized in the trigonal system (sp. gr. R3c, Z = 6). The unit-cell parameters are as follows: for I, a = 10.8720(5) Å, c = 38.121(1) Å; for II, a = 10.8652(5) Å, c = 38.098(1) Å; and for III, a = 10.8631(5) Å, c = 38.072(1) Å. In the structures of I and II, the M(1), M(2), and M(3) positions are statistically occupied by the rare-earth cations and calcium anions. In the structure of III, the Gd³⁺ cations occupy the _M(1) and _M(2) positions. The distributions of the R ³⁺ cations over the positions are characteristic of each structure. The composition of the cerium-ontaining compound Ca_9.81Ce_0.42(VO₄)₇ (a = 10.8552(5) Å, c = 38.037(1) Å) was refined and its crystal structure was solved from the X-ray powder data. In this compound, cerium atoms are in the oxidation states +3 and +4.     

Strontium in the collinsite structure: Rietveld refinement

The crystal structure of a strontium variety of a rare phosphate—mineral collinsite (Ca_{2 ? x}Sr_x)₂Mg[PO₄] · 2H₂O was solved from powder X-ray diffraction data (λ CuK_α radiation, Ni filter, 12.36° ≤ 2θ ≤ 100.00°, scan step 0.02°, exposure time per step 15 s) by the Rietveld method (R_wp = 4.15%, R_F = 1.03%, R_B = 2.46%); a = 5.8219(1) Å, b = 6.8319(2) Å, c = 5.4713(1) Å, α = 96.965(2)°, β = 108.846(2)°, γ = 107.211(2)°, sp. gr., \(\bar P1\), Z = 1, ρ_calcd = 3.12 g/cm³ (at x = 0.72). The new mineral was discovered in carbonatites from the Kovdor alkaline-ultrabasic massif. The crystallochemical data for collinsite were analyzed and compared with those for isotypic minerals of the fairfieldite group. Characteristic features of the low-temperature geochemistry of strontium were established.     

Synthesis and crystal structure of low ferrialuminosilicate sanidine

Iron-containing potassium feldspar crystals are prepared using the hydrothermal synthesis in an alkaline medium at temperatures ranging from 500 to 52°C. The crystal structure of the synthetic potassium feldspar is refined [Ital Structures diffractometer, MoKαradiation, 1327 unique reflections with Fs>σ(F), anisotropic approximation, R(F) = 0.044]. It is established that, under the given preparation conditions, the synthesis leads to the formation of the monoclinic modification with the following unit-cell parameters: a = 8.655(7) Å, b = 13.101(9) Å, c = 7.250(8) Å, β = 116.02(2)°, space group C2/m, and Z = 4. The cation distribution over crystallographically inequivalent tetrahedral positions T(1) and T(2) is determined and justified using X-ray diffraction data. According to this distribution, the iron-containing potassium feldspar is assigned to the low ferrialuminosilicate sanidine. The proposed structural formula K _{A = 0.99}(Si_1.2Fe_0.5Al_0.3)_{ΣT(1) = 2}(Si_1.81Al_0.19)_{ΣT(2) = 2}O₈ agrees well with the data of the electron microprobe analysis. It is revealed that iron occupies the T(1) position and manifests itself as a majority rather than minority impurity element with respect to aluminum.     

X-ray mapping in heterocyclic design: VII. Diffraction study of the structure of N-pyridoneacetic acid and the product of its intramolecular dehydration

The structure of pyridoneacetic acid C₇H₇N₁O₃(I) is determined by the single-crystal X-ray diffraction technique. The crystals of I are monoclinic, a = 7.4502(15) Å, b = 10.006(6) Å, c = 9.960(3) Å, β = 109.96(2)°, Z = 4, and space group P2₁/c. The structure of pyridoneacetic acid is solved by the direct method and refined by the least-squares procedure in the anisotropic approximation to R = 0.0387. The structure of the product of its intramolecular dehydration, C₇H₆N₁O₂B₁F₄(II), is determined by the grid search procedure and refined by the Reitveld method (R _p = 0.045, R _wp = 0.58, R _e = 0.026, and χ² = 4.69). The crystals of II are monoclinic, a = 10.4979(3) Å, b = 11.4467(3) Å, c = 7.6027(1) Å, β = 100.83(2)°, Z = 4, and space group P2₁/n. The system of two conjugated heterocycles is planar.     

Iron-rich schüllerite from Kahlenberg (Eifel,Germany): Crystal structure and relation to lamprophyllite-group minerals

A single-crystal sample of iron-rich schüllerite found at the Kahlenberg quarry in the Eifel paleovolcanic field (Germany) was studied by X-ray diffraction. The triclinic unit-cell parameters are as follows: a = 5.4061(1) Å, b = 7.0416(6) Å, c = 10.2077(7) Å, α = 99.86(1)°, β = 97.8(1)°, and γ = 89.98(1)°. The structure was solved by direct methods in sp. gr. P1 and refined to the R factor of 7.9% based on 4321 |F| > 6σ(F). The idealized formula is Ba₂Na(Ca,Mn)(Fe²⁺,Fe³⁺)MgTi₂[Si₂O₇]₂O₂(O,F)F. The new mineral differs from schüllerite by a lower sodium content and higher iron and calcium contents and is characterized by some distinguishing structural features. The dependence of the topology of layered HOH modules on the sodium content in schüllerite and lamprophyllite-group minerals and the character of regular intergrowths of these minerals are discussed.     

Coordination dimers constructed from metal(II) halides and the organic ligand 1,2-dimethoxy- 4,5-bis(2-pyridylethynyl)benzene

A series of new coordination compounds has been synthesized using the organic ligand 1,2-dimethoxy-4,5-bis(2-pyridylethynyl)benzene (dmpeb). The compounds all form dimers consisting of two metal cations bridged by two ligand molecules. Charge balance is provided by halide ligands, and the four-coordinate metal centers are distorted from the ideal tetrahedral environment. [CoCl₂(dmpeb)]₂ (1) crystallizes in the monoclinic space group P2₁/n with a = 8.5272(6) Å, b = 18.3653(13) Å, c = 13.3493(9) Å, β = 103.574(2)^°, V = 2032.2(2) ų, Z = 2. [ZnCl₂(dmpeb)]₂ (2) is isostructural to 1 and has the cell parameters a = 8.5495(4) Å, b = 18.4049(8) Å, c = 13.3692(6) Å, β = 103.4460(10)^°, V = 2046.01(16) ų, Z = 2. [ZnBr₂(dmpeb)]₂ (3) is also isostructural to 1 with a = 8.7882(5) Å, b = 18.7260(12) Å, c = 13.3857(8) Å, β = 102.5990(10)^°, V = 2149.8(2) ų, Z = 2. Additionally, the compounds [ZnI₂(dmpeb)]₂ (4, cell parameters: a = 8.9650(5) Å, b = 19.1251(10) Å, c = 13.4160(7) Å, β = 101.1660(10)^°, V = 2256.7(2) ų, Z = 2), [HgCl₂(dmpeb)]₂ (5, cell parameters: a = 8.8457(7) Å, b = 18.4030(15) Å, c = 13.3711(11) Å, β = 104.246(2)^°, V = 2109.7(3) ų, Z = 2), and [HgBr₂(dmpeb)]₂ (6, cell parameters: a = 9.0576(5) Å, b = 18.8634(11) Å, c = 13.4535(8) Å, β = 102.9780(10)^°, V = 2239.9(2) ų, Z = 2) are also isostructural to 1. A seventh dimeric compound, [HgI₂(dmpeb)]₂, not isostructural to the others was also characterized by X-ray crystallography. [HgI₂(dmpeb)]₂ (7) crystallizes in the triclinic space group P-1 with a = 8.8028(5) Å, b = 12.0990(7) Å, c = 12.4082(7) Å, α = 109.7240(10)^°, β = 107.3680(10)^°, γ = 93.0880(10)^°, V = 1169.57(12) ų, Z = 1.     

Crystal structures of two modifications of sodium pentahydrogendiphosphate NaH5(PO4)2

Two crystalline modifications of NaH₅(PO₄)₂ are obtained by the reaction of Na₂CO₃ with an excess of orthophosphoric acid. The crystal structures of α-and β-NaH₅(PO₄)₂ are determined by X-ray diffraction analysis. The crystal data are a = 8.484(4) Å, b = 7.842(3) Å, c = 10.353(4) Å, β = 90.50(3)°, V = 689.3(3) ų, space group P2₁/c, Z = 4, and R ₁ = 0.0250 for the α modification and a = 7.127(2) Å, b = 13.346(4) Å, c = 7.177(2) Å, β = 95.5(2)°, V = 679.5(3) ų, space group P2₁/c, Z = 4, and R ₁ = 0.0232 for the β modification. Based of the hydrogen-bond system, the formulas of the α and β modifications can be represented as Na(H₂PO₄)(H₃PO₄) and Na[H(H₂PO₄)₂], respectively. They correspond to the stable and metastable forms of the compound.     

Refined crystal structure of TR-fersmite (TR = Ce)

The structure of TR-fersmite (Ca_0.89Ce_0.11)(Nb_1.3Ti_0.7)O₅(O, OH) was refined to R = 0.032. The parameters of the orthorhombic unit cell are a = 5.762(2) Å, b = 14.988(8) Å, c = 5.246(1) Å, sp. gr. Pcan, Z = 4. The mixed A position is occupied by Ca and Ce atoms, and the mixed B position is occupied by Nb and Ti atoms.     

Crystal structure of [{MoBr2(O){OPH(OPr i )2}2}2(μ-O)]

[{MoBr₂(O){OPH(OPr ⁱ )₂}₂}₂(μ-O)] (1) crystallizes in the monoclinic space group P2₁/n, with a = 13.063(17) Å, b = 11.818(14) Å, c = 15.889(17) Å, β = 90.30(1)°, Z = 2. The dimeric structure contains a bridging oxygen atom at a crystallographic center of symmetry. Each octahedral molybdenum center has trans-bromide ligands, and two cis-OPH(OPr ⁱ )₂ units, with a terminal oxygen atom trans to one of the OPH(OPr ⁱ )₂ units.     

Crystal structure of Li2MgSiO4

The crystal structure of Li₂MgSiO₄ was established by single-crystal X-ray diffraction analysis. The crystals are monoclinic, a = 4.9924(7) Å, b = 10.681(2) Å, c = 6.2889(5) Å, β = 90.46(1)°, Z = 4, sp. gr. P2₁/n, V = 335.54 ų, R = 0.062. In a Li₂MgSiO₄ crystal, four types of independent T(1–4) tetrahedra share vertices to form a three-dimensional framework. Three of these tetrahedra are occupied simultaneously by Li and Mg cations, which corresponds to the crystallochemical formula (Li_0.98Mg_0.02)(Li_0.80Mg_0.20) · (Li_0.22Mg_0.78)SiO₄. In slightly distorted SiO₄ tetrahedra denoted as T(1), the average Si-O distance is 1.635(2) Å. The distortions of other tetrahedra and the average (Li _x Mg_{1 ? x} )-O distances increase with an increase in lithium content. These distances in the T(2), T(3), and T(4) tetrahedra are 1.955(2), 1.971(4), and 2.019(6) Å, respectively. The structure of the new compound is compared with the crystal structures of other Li₂ M ²⁺SiO₄ compounds and the luminescence spectra of Cr⁴⁺: Li₂MgSiO₄.     

The structure of solvate [Cu2(DfH)4(4,4′-Bipy)] · 2DMF

The crystal structure of [Cu₂(DfH)₄(4,4′-Bipy)] · 2DMF prepared by the reaction of copper(II) acetate with diphenylglyoxime (DfH₂) and 4,4′-bipyridine (4,4′-Bipy) was established by X-ray diffraction. The crystals are monoclinic; a = 15.5192(9) Å, b = 16.2427(11) Å, c = 14.0753(7) Å, β = 101.36(3)°, V = 3478.5(5) ų, Z = 2, and sp. gr. P2₁/c. The crystal structure is composed of discrete dinuclear molecules [Cu₂(DfH)₄(4,4′-Bipy)] and dimethylformamide (DMF) molecules. The coordination polyhedron of the Cu atom (the coordination number is 5) is a tetragonal bipyramid formed by the nitrogen atoms of two monodeprotonated bidentate oxime groups and the bidentate bridging 4,4′-Bipy ligand. The DMF molecules occupy the cavities formed by the dinuclear molecules [Cu₂(DfH)₄(4,4′-Bipy)]. The compound was characterized by IR and NMR spectroscopy.     

Solvent Dependant Ligand Displacement and Anion Coordination in Selected Copper(I) Coordination Compounds

The crystal structure of the Cu(I) mixed ligand salt, [Cu(MeCN)₂(PPh₃)₂](CF₃SO₃), 1, was determined using single crystal X-ray diffraction, a = 23.249(2), b = 26.665(1), c = 19.4201(9) Å β = 102.614(1) Å, in the P2₁/c space group. The packing of this complex is quite similar to the PF₆ ^?, BF₄ ^?, and ClO₄ ^? analogs but contains three crystallographically unique [Cu(MeCN)₂(PPh₃)₂](CF₃SO₃) complexes per asymmetric unit (instead of one). Upon dissolution and recrystallization of this salt in either toluene or tetrahydrofuran, anion (and solvent) coordination results in the formation of two new neutral species Cu(PPh₃)₂(CF₃SO₃)(MeCN) 2 and Cu(PPh₃)₂(CF₃SO₃)(THF) 3, respectively. Both 2 and 3 crystallize in the orthorhombic Pca2₁ space group with a = 22.533(1), b = 9.0688(5), c = 18.4689(9) Å, and a = 22.434(1), b = 8.9789(5), c = 18.418(1) Å, respectively. With the perchlorate anion, [Cu₂(ClO₄)(MeCN)(PPh₃)₄(THF)](ClO₄) 4, is isolated, which crystallizes in the monoclinic space group C2/c with a = 27.308(1), b = 28.064(1), c = 21.448(1) Å, and β = 120.342(1)°. Surprisingly, it is comprised of an analogous solvent coordinated neutral molecule, Cu(PPh₃)₂(THF)_0.8(MeCN)_0.2(ClO₄) together with an anion-bridged dimeric species, [Cu₂(PPh₃)₄(MeCN)_1.6(THF)_0.4(ClO₄)]⁺, charge balanced by one additional non-coordinated ClO₄ ^? anion. The coordinated solvent molecules are disordered in both moieties. Compounds 1–3 were further characterized using thermal gravimetric analysis.     

Crystal structure of [Pb(cis-anti-cis-dicyclohexyl-18-crown-6)(OH2)2][ClO4]2

[Pb(cis-anti-cis-dicyclohexyl-18-crown-6)(OH₂)₂][ClO₄]₂ was crystallized using a slightly modified literature method for the separation of dicyclohexyl-18-crown-6 isomers. It crystallizes in the monoclinic space groupP2₁/n witha=8.415(5),b=20.993(9),c=8.973(5) Å, β=111.56(6)^o, andD _calc=1.84 g/cm³ for Z=2. The Pb²⁺ ion resides on a crystallographic center of inversion and is coordinated to the six crown ether donors and two axial water molecules in a hexagonal bipyramidal geometry. The Pb-O(etheric) distances range from 2.694(4) to 2.743(4) Å while the Pb?OH₂ distance is 2.522(6) Å.     

Crystal Structures of 6-methyl-3-phenylsulfonylchroman-4-one andtrans-6-methyl-3-phenylsulfonylchroman-4-ol

The crystal structures of (i) CH₃(C₉H₆O₂)SO₂C₆H₅ and (ii) CH₃(C₈H₈O₂)SO₂?C₆H₅ have been determined by X-ray diffraction. (i) crystallizes in the monoclinic space groupP2₁/c with unit cell parametersa=8.814(1)Å,b=10.310(1)Å,c=15.841(4)Å, β=98.17(1)^o, andZ=4, and (ii) crystallizes in the orthorhombic space groupP2₁2₁2₁ with unit cell parametersa=6.206(1)Å,b=11.752(5)Å,c=19.865(3)Å, andZ=4. The pyran ring in both of them is in the distorted half-chair conformation with differeing degrees of distortion from the ideal.     

Crystal structures of two platinum-bipyrimidine complexes: Pt(bpm)Cl2·dmf and Pt(bpm)(dmso)(SO4)·H2O

Red Pt(bpm)Cl₂·dmf forms a stacked structure which has Pt…Pt separations of 3.423(2) A and 3.447(2) Å with Pt…Pt…Pt angles of 155.39(3)^o. The unit cell isP-1, witha=6.712(4) A,b=10.0765(6) Å,c=11.551(3) Å, α=106.732(12)^o, β=103.65(4)^o, γ=90.46(3)^o, andZ=2. The structure refined to anR(F) of 0.046 using 181 parameter and 2165 reflections withI>1σ(I). The yellow complex Pt(bpm)(dmso)(SO₄)·H₂O does not stack in the solid state: the shortest Pt…Pt separation is 4.638(2) Å. The unit cell is alsoP-1, witha=8.060(3) A,b=9.560(3) A,c=9.7534(18) Å, α=90.62(2)^o, β=99.43(3)^o, γ=90.66(3)^o, andZ=2. The structure refined to anR(F) of 0.039 using 208 parameters and 3689 reflections withI>1σ(l).