Crystal structure of new micalike titanosilicate—bussenite,Na<Subscript>2</Subscript>Ba<Subscript>2</Subscript>Fe<Superscript>2+</Superscript>[TiSi<Subscript>2</Subscript>O<Subscript>7</Subscript>][CO<Subscript>3</Subscript>]O(OH)(H<Subscript>2</Subscript>O)F

The crystal structure of mineral bussenite, Na₂Ba₂Fe[TiSi₂O₇][CO₃]O(OH)(H₂O)F, found in the Khibiny massif (the Kola Peninsula) has been determined. The parameters of the triclinic unit-cell are a = 5.399(3) Å, b = 7.016(9) Å, c = 16.254(14) Å, α = 102.44(8)°, β = 93.18(6)°, γ = 90.10(7)°, sp. gr. \(P\bar 1\), R = 0.054 for 1418 reflections with |F| > 2.5σ(F). The mineral studied belongs to the family of layered titanosilicates, in which, unlike the sulfate-and phosphate-containing representatives of this family, the interlayer spaces are filled with carbonate groups.     

Crystal structures of oxalate-bearing cancrinite with an unusual arrangement of CO<Subscript>3</Subscript> groups and sulfate-rich davyne

The crystal structures of two unusual varieties of cancrinite-group minerals—oxalate-bearing cancrinite from the Kovdor massif (Kola Peninsula) and the sulfate end member of the davyne series from the Sar-e Sang mine (Badakhshan, Afghanistan)—were studied by single-crystal X-ray diffraction. The unit-cell parameters of the hexagonal cells are a = 12.688(4) Å, c = 5.189(1) Å and a = 12.773(1) Å, c = 5.334(1) Å, sp. gr. P6₃; the R factors are 0.034 and 0.035, respectively. The presence of oxalate groups in cancrinite as admixtures is one of the factors responsible for the shift of CO₃ groups in wide channels.     

Crystal chemistry of elpidite from Khan Bogdo (Mongolia) and its K- and Rb-exchanged forms

Elpidite Na₂ZrSi₆O₁₅ · 3H₂O [space group Pbcm, a = 7.1312(12), b = 14.6853(12), and c = 14.6349(15) Å] from Khan Bogdo (Mongolia) and its K- and Rb-exchanged forms K_1.78Na_0.16H_0.06ZrSi₆O₁₅ · 0.85H₂O [Cmce, a = 14.054(3), b = 14.308(3), and c = 14.553(3) Å] and Na_1.58Rb_0.2H_0.22ZrSi₆O₁₅ · 2.69H₂O [Pbcm, a = 7.1280(10), b = 14.644(3), and c = 14.642(3) Å] that were obtained by cation exchange at 90°C, as well as K_1.84Na_0.11H_0.05ZrSi₆O₁₅ · 0.91H₂O [Cmce, a = 14.037(3), b = 14.226(3), and c = 14.552(3) Å] and Rb_1.78Na_0.06H_0.16ZrSi₆O₁₅ · 0.90H₂O [Cmce, a = 14.2999(12), b = 14.4408(15), and c = 14.7690(12) Å], obtained at 150°C are studied by single-crystal X-ray diffraction and IR spectroscopy. The base of the structures is a heteropolyhedral Zr-Si-O framework whose cavities accommodate Na (K, Rb) cations and H₂O molecules.     

Crystal structure of hydrogen-bearing vuonnemite from the Lovozero alkaline massif

Hydrogen-bearing vuonnemite from the Shkatulka hyperagpaitic pegmatite (the Lovozero alkaline massif, Kola Peninsula) was studied by single-crystal X-ray diffraction. The triclinic unit-cell parameters are as follows: a = 5.4712(1) Å, b = 7.1626(1) Å, c = 14.3702(3) Å, α = 92.623(2)°, β = 95.135(1)°, γ = 90.440(1)°, sp. gr. P1, R = 3.4%. The Na⁺ cations and H₂O molecules are ordered in sites between the packets. The water molecules are hydrogen bonded to the PO₄ tetrahedra.     

New Data on Isomorphism in Eudialyte-Group Minerals. I. Crystal Structure of Titanium-Rich Eudialyte from the Kovdor Alkaline Massif

An abnormally titanium-rich mineral of the eudialyte group was studied by IR spectroscopy and X-ray diffraction. The trigonal unit cell parameters are a = 14.165(1) Å, c = 30.600(5) Å, V = 5317.23(4) ų, sp. gr. R3m. The crystal structure was refined to R = 0.034 with anisotropic displacement parameters using 2530 reflections with F > 3σ(F). The idealized formula of the mineral (Z = 3) is Na₈(H₃O)₅(K,Ce,Sr)₂Ca₆Zr₂Ti_1.2(Fe,Mn)_0.6Si₂₆O₇₂(OH)₂Cl · 4H₂O. At the ratio Zr: Ti ~ 2: 1, titanium atoms lie in four sites and are not predominant in any of them. Another distinguishing feature of the mineral is the structural separation of chemical elements, such that K, Sr, and Ce cations and H₃O groups are randomly distributed between four split sites to form polyhedra with different volumes. The isomorphism of Zr and Ti in eudialyte-group minerals is discussed.     

Modular structure of highly ordered eudialyte and its place among hydrated minerals of rastsvetaevite family

The crystal structure of a representative of eudialyte group, which was found by A.P. Khomyakov at the Rasvumchorr mountain of the Khibiny alkaline massif (Kola Peninsula), has been studied by X-ray diffraction. The trigonal unit-cell parameters are found to be a = 14.2328(5) Å, c = 60.217(2) Å, V = 10564.08(3) Å3, sp. gr. R3m. The structure has been refined with the isotropic and anisotropic approximation displacement parameters to the total reliability factor R = 5.6%, based on 2989 reflections with |F| > 4σ(F). The idealized formula (Z = 3) is determined as [(H₃O)₁₁Na₁₀K5]Cа₁₂(Na₃Fe₂Mn)Si₄Zr₆(Si₄₈O₁₄₄)(OH,Cl)₅(H₂O)₅. The unit cell of the mineral is doubled due to the presence of two modules of different composition and structure in it (alluaivite-and kentbrooksite-like ones) and the formation of a polyhedral cluster in the kentbrooksite module. A comparison with two hydrated minerals having a modular structure shows that these minerals, being similar in their chemical composition, differ in the cation ordering over the sites of the two modules. The sample under study contains potassium in only one module, while oxonium groups are distributed in both modules but over different sites.     

Crystal structure of the NaCa(Fe<Superscript>2+</Superscript>, Al,Mn)<Subscript>5</Subscript>[Si<Subscript>8</Subscript>O<Subscript>19</Subscript>(OH)](OH)<Subscript>7</Subscript> · 5H<Subscript>2</Subscript>O mineral: A new representative of the palygorskite group

A specimen of a new representative of the palygorskite-sepiolite family from Aris phonolite (Namibia) is studied by single-crystal X-ray diffraction. The parameters of the triclinic (pseudomonoclinic) unit cell are as follows: a = 5.2527(2) Å, b = 17.901(1) Å, c = 13.727(1) Å, α = 90.018(3)°, β = 97.278(4)°, and γ = 89.952(3)°. The structure is solved by the direct methods in space group P \(\bar 1\) and refined to R = 5.5% for 4168 |F| > 7σ(F) with consideration for twinning by the plane perpendicular to y (the ratio of the twin components is 0.52: 0.48). The crystal chemical formula (Z = 1) is (Na_1.6K_0.2Ca_0.2)[Ca₂(Fe _3.6 ²⁺ Al_1.6Mn_0.8)(OH)₉(H₂O)₂][(Fe _3.9 ²⁺ Ti_0.1)(OH)₅(H₂O)₂][Si₁₆O₃₈(OH)₂] · 6H₂O, where the compositions of two ribbons of octahedra and a layer of Si tetrahedra are enclosed in brackets. A number of specific chemical, symmetrical, and structural features distinguish this mineral from other minerals of this family, in particular, from tuperssuatsiaite and kalifersite, which are iron-containing representatives with close unit cell parameters.     

Catenated molecular pattern in the crystal structure of a copper(II) complex with pyrazine-2,6-dicarboxylic acid and chloride ligands

The crystals of catena-dichloro-(dihydrogen pyrazine-2,6-dicarboxylato-O,O′,N,-N′) copper(II) dihydrate Cu[H₂(2,6-PZDC)]Cl₂?2H₂O are monclinic, space group C2/c with a = 11.658(2) Å, b = 6.778(1) Å, c = 16.390(3) Å, β = 98.90(3)^°, and Z = 4. Two adjacent copper(II) ions are bridged by a fully protonated pyrazine-2,6-dicarboxylic acid molecule which uses for bridging its O,O′,N-bonding moiety on one side and a single hetero-ring nitrogen atom on the other. Two chloride ions in axial position complete the octahedral coordination around the metal ions with bond distances: Cu–N 2.027(3) ÅA, Cu–N′ 2.005(3) ÅA, Cu–Cl. 2.281(1) ÅA, and Cu–O 2.446(2) ÅA. Copper(II) ions are located in the center of symmetry and are coplanar with the ligand acid molecule forming flat molecular chains propagating in the direction of the b axis. Hydrogen bonds via solvation water molecule link the chains into molecular layers parallel to the ac plane. Weak van der Waals type interactions operate between the layers.     

Structural model of uramarsite

The structural model of uramarsite, a new mineral of the uran-mica family from the Bota-Burum deposit (South Kazakhstan), is determined using a single-crystal X-ray diffraction analysis. The parameters of the triclinic unit cell are as follows: a = 7.173(2) Å, b = 7.167(5) Å, c = 9.30(1) Å, α = 90.13(7)°, β = 90.09(4)°, γ = 89.96(4)°, and space group P1. The crystal chemical formula of uramarsite is: (UO₂)₂[AsO₄][PO₄,AsO₄][NH₄][H₃O] · 6H₂O (Z = 1). Uramarsite is the second ammonium-containing mineral of uranium and an arsenate analogue of uramphite. In the case of uramarsite, the lowering of the symmetry from tetragonal to triclinic, which is accompanied by a triclinic distortion of the tetragonal unit cell, is apparently caused by the ordering of the As and P atoms and the NH₄, H₃O, and H₂O groups.     

The crystal structure of vyuntspakhite: A redetermination

The crystal structure of the mineral vyuntspakhite (Y, TR)₆{Al₂(OH)₃[H_1.48Si_1.88O₇][SiO₄][SiO₃(OH)]}₂(a = 5.7551(11) Å, b = 14.752(3) Å, c = 15.906(4) Å, β = 96.046(4)°, sp. gr. P2₁/n, Z = 2), which had been established earlier in the pseudo-unit cell, is redetermined by X-ray diffraction (R = 0.040, T = 100 K). The redetermination of the structure shows that pronounced pseudotranslation along the axis c′ = c/3 is associated with the fact that Y(TR) atoms are related by a 1/3 translation along the [001] direction. Most of the hydrogen atoms are located. The crystal-chemical function of hydrogen bonds is analyzed. In the unit cell of vyuntspakhite, the cationic layers consisting of edge-sharing (Y,TR) eight-vertex polyhedra alternate along the b axis with mixed anionic layers composed of isolated Si tetrahedra (orthotetrahedra), Si₂O₇ double-tetrahedra (diortho) groups, Al five-vertex polyhedra, and Al₂O₈ double-tetrahedra groups linked by shared vertices and through hydrogen bonding.     

Synthesis,thermal analysis,and crystal structure of manganese(II) 9-molybdocobaltate(III)

Manganese(II) 9-molybdocobaltate(III) of the composition [Mn(H₂O)₄] · [CoMo₉O₂₇(OH)₅] · 7H₂O (I) has been synthesized for the first time and investigated using X-ray diffraction and thermal gravimetric analyses. Compound I crystallizes in the trigonal system with the following unit cell parameters: a = 15.926(1) Å, c = 12.363(1) Å, V = 2715.6(4) ų, M = 1692.55, Z = 3, ρ_(calcd) = 3.105 g/cm³, space group R32.     

Synthesis and crystal structure of [UO<Subscript>2</Subscript>CrO<Subscript>4</Subscript>(C<Subscript>5</Subscript>NH<Subscript>5</Subscript>COO)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)]·2H<Subscript>2</Subscript>O

Crystals of UO₂CrO₄(C₅NH₅COO)₂(H₂O)] · 2H₂O are synthesized and their structure is studied by X-ray diffraction. The compound crystallizes in the triclinic crystal system. The unit cell parameters are as follows: a = 7.0834(10) Å, b = 10.6358(14) Å, c = 12.9539(17) Å, α = 75.096(2)°, β = 74.490(2)°, and γ = 80.657(2)°; V = 904.1(2) ų, space group P \(\bar 1\), Z = 2, and R = 0.026. The structure is built of [UO₂CrO₄(C₅NH₅COO)₂(H₂O)]₂ centrosymmetric dimers, which are linked into a framework by a system of hydrogen bonds involving inner-sphere and outer-sphere water molecules. The coordination number of the U(VI) atom is seven, and the coordination polyhedron is a pentagonal bipyramid with the oxygen atoms of the uranyl group, two chromate groups, two molecules of isonicotinic acid, and a water molecule at the vertices. The crystal chemical formula of the [UO₂CrO₄(C₅NH₅COO)₂(H₂O)]₂ dimer is represented as AB ² M ₃ ¹ , where AB ² M ₃ ¹ , where A = UO ₂ ²⁺ , B ² = CrO ₄ ^2? , and M ¹ = = C₅NH₄COOH and H₂O.     

Crystal structure of zinc(II) hydrated trinuclear complex with monoprotonated ethylenediaminetetraacetate anion(3−), [Zn<Subscript>3</Subscript>(H<Emphasis Type="Italic">Edta</Emphasis>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>]

The crystal structure of the [Zn₃(HEdta)₂(H₂O)₆] complex (I) is determined by X-ray diffraction analysis. The crystals are orthorhombic, a = 14.780 Å, b = 29.699 Å, c = 7.032 Å, Z = 4, and space group Pna2₁. The structural units of crystals I are trinuclear linear molecules, in which the peripheral atoms Zn(1) and Zn(2) each coordinate two N atoms and three O atoms of the HEdta ^3? ligand and the O(w) atom of the H₂O molecule, whereas the central Zn(3) atom coordinates four O(w) atoms of the H₂O molecules and two terminal O atoms of the two HEdta ^3? ligands. The HEdta ^3? ligand fulfills a hexadentate chelating—bridging function. The bond lengths are as follows: Zn-O(HEdta), 2.006(4)–2.123(4) Å; Zn-N, 2.214(6) and 2.128(5) Å; and Zn-O(w), 2.006(6)–2.225(5) Å. In structure I, there is a specific contact formed by hydrogen bonds, owing to which the distance between the central atoms of individual molecules appears to be shorter than that in covalently bonded complexes.     

Crystal structure of modular sodium-rich and low-iron eudialyte from Lovozero alkaline massif

The structure of the sodium-rich representative of the eudialyte group found by A.P. Khomyakov at the Lovozero massif (Kola Peninsula) is studied by X-ray diffraction. The trigonal cell parameters are: a = 14.2032(1) and c = 60.612(1) Å, V = 10589.13 Å3, space group R3m. The structure is refined to the final R = 5.0% in the anisotropic approximation of atomic displacement parameters using 3742|F| > 3σ(F). The idealized formula (Z = 3) is Na₃₇Ca₁₀Mn₂FeZr₆Si₅₀(Ti, Nb)₂O₁₄₄(OH)₅Cl₃ · H₂O. Like other 24-layer minerals of the eudialyte group, this mineral has a modular structure. Its structure contains two modules, namely, “alluaivite” (with an admixture of “eudialyte”) and “kentbrooksite,” called according to the main structural fragments of alluaivite, eudialyte, and kentbrooksite. The mineral found at the Lovozero alkaline massif shows some chemical and symmetry-structural distinctions from the close-in-composition labyrinthite modular mineral from the Khibiny massif. The difference between the minerals stems from different geochemical conditions of mineral formation in the two regions.     

Refined structure of afwillite from the northern Baikal region

The crystal structure of the mineral afwillite [Ca₁₂(H₂O)₈][SiO₄]₄[SiO₂(OH)₂]₄ from the northern Baikal region was refined in a triclinic unit cell with the following parameters: a = 16.330(2) Å, b = 5.6389(6) Å, c = 11.685(1) Å, α = 90.08(1)°, β = 126.446(2)°, γ = 89.95(1)°, and sp. gr. P1. The triclinic unit cell is related to the monoclinic unit cell determined earlier (sp. gr. Cc, a = 16.278(1) Å, b = 5.6321(4) Å, c = 13.236(1) Å, and β = 134.898(3)°) by the transformation matrix [?100/010/101]. The structural model was determined using the phase-correction procedure and refined anisotropically to R = 2.8% based on 3270 independent reflections with F > 3σ(F). The crystal-chemical formula of afwillite was revised. The characteristic features of the IR spectrum of afwillite were explained based on the structural data.     

Structure and some properties of [UO<Subscript>2</Subscript>(C<Subscript>5</Subscript>H<Subscript>12</Subscript>N<Subscript>2</Subscript>O)<Subscript>5</Subscript>](ClO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Compound [UO₂(C₅H₁₂N₂O)₅](ClO₄)₂ is synthesized and characterized by thermogravimetry, IR spectroscopy, and X-ray diffraction. The compound crystallizes in the monoclinic crystal system; a = 15.2985(9) Å, b = 26.9676(15) Å, c = 20.6962(11) Å, β = 100.697(1)°, space group P2₁/c, Z = 8, and R = 0.0445. Discrete [UO₂(C₅H₁₂N₂O)₅]²⁺ groups belonging to the AM ₅ ¹ crystal chemical group of uranyl complexes (A = UO ₂ ²⁺ and M ¹=C₅H₁₂N₂O) are uranium-containing structural units of the crystals.     

First example of lanthanide coordination polymer of 2,5-pyrazinedicarboxylate

A lanthanum coordination polymer, [La(2,5-PZDC)_1.5(H₂O)] _n , (2,5-PZDC = 2,5-pyrazinedicarboxylate) has been synthesized by using the reaction of LaCl₃?7H₂O with 2,5-pyrazinedicarboxylic acid under hydrothermal condition and structurally characterized by X-ray diffraction method. It crystallizes in the triclinic system P \(\bar 1\) with a = 6.297(2) Å, b = 6.762(2) Å, c = 13.450(4) Å, α = 82.984(5)^°, β = 83.164(5)^°, γ = 63.260(4)^°, V = 506.3(3) ų, Z = 2. The La³⁺ ion is nine-coordinate in a N₂O₇ environment, with a tricapped trigonal prism geometry, and the ligand 2,5-pyrazinedicarboxylate adopts two coordination modes, through which lanthanum ions are linked together to form a three-dimensional structure.     

Crystal structure of golyshevite

The crystal structure of golyshevite, a new calcium-and carbon-rich representative of the eudialyte group, was established by single-crystal X-ray diffraction analysis (sp. gr. R3m, a = 14.231(3) Å, c = 29.984(8) Å, R = 0.062, 1643 reflections with F > 3σ(F)). The idealized formula of golyshevite is (Na₁₀Ca₃)Ca₆Zr₃Fe₂SiNb[Si₃O₉]₂[Si₉O₂₇]₂(OH)₃(CO₃) · H₂O. This mineral is characterized by the presence of calcium atoms both in the octahedral positions of six-membered rings and in extraframework positions, where calcium prevails. CO₃ groups are present as the major additional anions. Carbon atoms randomly occupy two positions on the threefold z axis at a distance of 0.75 Å from each other and are coordinated by oxygen atoms arranged around the z axis.     

Crystal structure of a new ten-layer feldspathoid of the cancrinite group

A new cancrinite-group mineral with composition (Na,Ca)₂₄K₁₀[(Si,Al)₆₀O₁₂₀](SO₄)_5.6Cl_1.5(CO₃)_0.4·11H₂O from the Sacrofano Caldera (Italy) was studied by X-ray diffraction. The unit-cell parameters are a = 12.847 Å, c = 26.461 Å, sp. gr. P3; the R factor is 5.7% based on 3111 reflections with F > 5σ(F). The mineral has a ten-layer stacking sequence of six-membered rings ACACBCBCBCAC…, whereas franzinite (Na,K)₃₀Ca₁₀[Si₃₀Al₃₀O₁₂₀](SO₄)₁₀·2H₂O having the same unit cell (sp. gr. P321) is characterized by a stacking sequence ABCABACABCAB. Both minerals contain three types of cages, including the cancrinite cage. The distinguishing feature of the analog of franzinite is that it contains the largest cages (liottite and giuseppettite) instead of the sodalite and bystrite (losod) cages found in the franzinite structure.     

Synthesis and crystal structure of Na<Subscript>3</Subscript>(H<Subscript>3</Subscript>O)[UO<Subscript>2</Subscript>(SeO<Subscript>3</Subscript>)<Subscript>2</Subscript>]<Subscript>2</Subscript>· H<Subscript>2</Subscript>O

Single crystals of the compound Na₃(H₃O)[UO₂(SeO₃)₂]₂ · H₂O (I) have been synthesized, and their structure has been investigated using X-ray diffraction. Compound I crystallizes in the triclinic system with the unit cell parameters a = 9.543(6)Å, b = 9.602(7)Å, c = 11.742(8)Å, α = 66.693(16)°, β = 84.10(2)°, γ = 63.686(14)°, space group P \(\bar 1\), Z = 2, and R = 0.0734. The uranium-containing structural units of the crystals are [UO₂(SeO₃)₂]^2? chains, which belong to the crystal-chemical group AB ² B ¹¹ (A = UO ₂ ²⁺ , B ² = SeO ₃ ^2? , B ¹¹ = SeO ₃ ^2? ) of the uranyl complexes. The structures of the compounds containing the [UO₂(SeO₃)₂]^2? anionic complexes are compared.