The Fe<Superscript>2+</Superscript>/Fe<Superscript>3+</Superscript> ratio in natural and heat-treated iron-rich eudialytes

The structures of natural iron-rich eudialyte (specimen 3458 from the Khibiny massif, the Kola Peninsula) and two heat-treated samples of this mineral calcined at 700 and 800°C were determined by X-ray diffraction. The trigonal unit-cell parameters (sp. gr. R3m) are as follows: a = 14.2645(1) Å, c = 29.9635(5) Å; a = 14.1307(1) Å, c = 30.1229(3) Å; a = 14.1921(2) Å, c = 30.2417(5) Å, respectively. It was found that Fe³⁺ ions in the calcined eudialytes, as well as impurities in the starting specimen, occupy the square-pyramidal Fe³⁺(V) sites, whereas Fe²⁺ ions are in the planar-tetragonal Fe²⁺(IV) sites.     

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.     

Structural characteristics of Na,Fe-decationated eudialyte with the symmetry <Emphasis Type="Italic">R</Emphasis>3

The crystal structure of a new highly decationated representative of the eudialyte group has been established (R = 0.055, 1734 |F|). The mineral is described by the simplified formula (H₃O)₉Na₂(K, Ba,Sr)₂Ca₆Zr₃[Si₂₆O₆₆(OH)₆](OH)₃Cl · H₂O (Z = 3). The unit-cell parameters are a = 14.078(3) Å, c = 31.24(1) Å; V = 5362 ų; sp. gr. R3. Being chemically and structurally related to the hydrated analogues studied previously (in particular, to potassium oxonium eudialyte), the new mineral differs from its analogues in that it has a higher degree of Na-and Fe-cation depletion. The replacement of 3/4 of Na cations by loose and mobile H₃O groups results in structure destabilization, which is seen from the high values of the thermal parameters of the atoms and the loss of the symmetry plane.     

Crystal Structure of Cl-Deficient Analogue of Taseqite from Odikhincha Massif

An eudialyte group mineral, found in pegmatites of the Odikhincha massif (the northern part of the Siberian platform), has been investigated using X-ray diffraction, IR spectroscopy, and Raman spectroscopy. The mineral is characterized by a high strontium content and a low chlorine content. It has a trigonal unit cell with the following parameters: a = 14.2700(6) Å and c = 30.057(1) Å; V = 5300.6(1) ų; sp. gr. R3m. The structure has been refined to R = 0.047 in the anisotropic approximation of atomic displacements using 1697F > 4σ(F). The idealized formula (Z = 3) was found to be Na₁₂Sr₂Ca₆Fe ₃ ²⁺ Zr₃NbSi₂₅O₇₂(OH,O)₄Cl(Н₂О)_0.2. The chemical composition and structure of this mineral are close to those of taseqite; however, it differs from the holotype sample by a low chlorine content and peculiarities of cation distribution over basic structure sites. A comparative analysis of strontium-rich eudialytes has revealed their important crystallochemical feature: selective concentration of strontium in the N4 site. Thus, taseqite, along with heterophyllosilicates, may play a role of strontium concentrator in agpaitic pegmatites.     

Refinement of the crystal structure of Zn-containing greifensteinite

The crystal structure of Zn-containing greifensteinite from the Pirineus Mine (Minas Gerais, Brazil) was refined (R = 0.045, 562 reflections with |F| > 2σ(F)). The unit-cell parameters are a = 15.941(3) Å, b = 11.877(3) Å, c = 6.625(2) Å, β = 95.09(2)°; V = 1249.4 ų; sp. gr. C2/c; and Z = 2. The idealized formula is [Mn(Fe²⁺, Zn)₄]Ca₂Be₄(PO₄)₆(OH)₄ · 6H₂O. The mineral is isostructural with the previously studied monoclinic representatives of the roscherite group from different deposits and differs from these representatives in that it contains Zn in one of two octahedral positions.     

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.     

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.     

Molecular structures of chalcone podands: A prognosis of photoinduced transformations in the crystals

A series of chalcone podands with the propenone group in the ortho position of the bridging aryl substituent with respect to the oxyethylene fragment is synthesized. The influence of the preorganization of the chalcone podand molecules in crystals on their ability to participate in topochemical reactions is investigated. From analyzing the X-ray structural data, the highest probability of the solid-state photochemical [2 + 2]cycloaddition is predicted for podands with phenyl substituents and the oxyethylene fragment containing two or three oxygen atoms. The X-ray structural data for the chalcone podand C₃₂H₂₆O₄ (3a) are as follows: a = 7.904(9) Å, b = 14.92(2) Å, c = 21.30(3) Å, β = 91.7(1)°, monoclinic system, space group P2₁/c, Z = 4, V = 2510(5) ų, ρ = 1.26 g/cm³, and R = 0.046; C₃₄H₃₀O₅ (3b): a = 15.738(9) Å, b = 11.889(2) Å, c = 15.0830(15) Å, β = 105.47(14)°, monoclinic system, space group C2/c, Z = 4, V = 2720.0(9) ų, ρ = 1.266 g/cm³, and R = 0.0418; C₃₂H₂₄N₂O₈ (4a): a = 17.9416(18) Å, b = 10.9703(8) Å, c = 41.699(2) Å, β = 105.970(11)°, monoclinic system, space group P2₁/c, Z = 4, V = 2781.4(5) ų, ρ = 1.348 g/cm³, and R = 0.0426; C₃₆H₃₂N₂O₁₀ (4c): a = 7.6286(5)Å, b = 17.9398(10) Å, c = 11.5890(3)Å, β = 95.287(4)°, monoclinic system, space group P2₁/n, Z = 2, V = 1579.27(14) ų, ρ = 1.372 g/cm³, and R = 0.0377; and C₂₈H₂₂O₆ (5a): a = 15.6032(10) Å, b = 8.1131(5) Å, c = 17.7334(11) Å, β = 91.381(5)°, monoclinic system, space group C2/c, Z = 4, V = 2244.2(2) ų, ρ = 1.345 g/cm³, and R = 0.0309.     

Synthesis and crystal structure of 2-acetylnaphthalen-6-yl 4-methylbenzosulfonate

The title compound has been synthesized by the reaction of 1-(6-hydroxy-2-naphthyl)-1-ethanone (2) with p-toluenesulfonyl chloride. Its structure was determined by single crystal X-ray diffraction. 2-Acetylnaphthalen-6-yl 4-methylbenzosulfonate (3) crystallizes in the orthorhombic space group Pbca with a = 12.727(3) Å, b = 14.560 (3) Å, c = 17.688 (4) Å, V = 3277.8 (11) ų, and Z = 8. The results demonstrate that the dihedral angle between the benzene ring and the naphthalene ring is 116.5^°, and the length (1.417 Å) of single C–O bond of 3 is longer than that of single C–O bond in the relative compounds.     

Structural characteristics of a new cation-deficient representative of the labuntsovite group

The crystal structure of a new representative of the labuntsovite group from the Khibiny massif (the Kola Peninsula) has been refined. The unit-cell parameters are a = 14.298(7) Å, b = 13.816(7) Å, c = 7.792(3) Å, β = 116.85(5)°, V = 1373.3 ų, sp. gr. C2/m, R^aniso = 0.047, 1084 reflections with F > 4σ (F). The mineral differs from lemmleinite-Ba and other members of the group by the predominance of the vacancies in two key cationic positions—C position is occupied by Ba cations (37%) and D position is occupied mainly by Mn cations (47%).     

X-ray diffraction investigation of <Emphasis Type="Italic">trans</Emphasis>-2,8-dihydroxy-2,4,4′, 6,6′,8,10,10′,12,12′-decamethyl-5,11-dicarbacyclohexasiloxane and <Emphasis Type="Italic">trans</Emphasis>-1,4-dihydroxy-1,4-dimethyl-1,4-disilacyclohexane

The crystal structures of two organosilicon compounds are studied by X-ray diffraction. Crystals of trans-2,8-dihydroxy-2,4,4′,6,6′,8,10,10′,12,12′-decamethyl-5,11-dicarbacyclohexasiloxane, C₁₂H₃₆O₆Si₆, (I) are studied at 293 K [a = b = 16.310(4) Å, c = 9.849(3) Å, V = 2620(1) ų, d_calcd = 1.128 g/cm³, space group P4(2)/n, Z = 4, 3370 reflections, wR2 = 0.1167, R1 = 0.0472 for 2291 reflections with F > 4σ(F)]. Crystals of trans-1,4-dihydroxy-1,4-dimethyl-1,4-disilacyclohexane, C₆H₁₆O₂Si₂, (II) are studied at 110 K [a = 6.8253(5) Å, b = 9.5495(8) Å, c = 12.0064(10) Å, α = 101.774(2)°, β = 102.203(2)°, γ = 95.068(2)°, V = 741.8(1) ų, d_calcd = 1.184 g/cm³, space group \(P\bar 1\), Z = 3, 6267 reflections, wR2 = 0.1052, R1 = 0.0421 for 3299 reflections with F > 4σ(F)]. It is found that the conformation of the ring in compound I, which contains two methylene groups in the cyclohexasiloxane ring, differs from those in its analogues containing only oxygen atoms or one methylene group in the ring. The noticeable difference between the SiCSi angle [123.0(2)°] and the tetrahedral angle is characteristic of cyclohexasiloxanes. Structure II contains three independent molecules with very close conformations. The cyclohexane rings adopt a chair conformation. The methylene groups in II, in distinction to those in I, are characterized by a standard tetrahedral coordination.     

Characteristic structural features of a tantalum-rich eudialyte variety from Brazil

The crystal structure of a new tantalum-rich variety of the mineral eudialyte discovered in Brazil was established by X-ray diffraction analysis (sp. gr. R3m, R = 0.038, 1092 independent reflections). The structural characteristic of this mineral is the presence of Ta atoms in the specific positions in the centers of planar “squares” with Ta-O distances ranging from 2.035(7) to 2.116(8) Å. Two additional oxygen atoms located at distances of 2.44 and 2.66 Å can complete these “squares” to strongly distorted octahedra.     

Crystal structure of ilyukhinite,a new mineral of the eudialyte group

The crystal structure of ilyukhinite, a new mineral of the eudialyte group, is studied by X-ray diffraction. The mineral found in pegmatite bodies of the Kukisvumchorr Mountain (Khibiny alkaline complex) is characterized by low sodium content, high degree of hydration, and predominance of manganese over iron. The trigonal cell has the following parameters: a = 14.1695(6) and c = 31.026(1) Å; space group R3m. The structure is refined to final R = 0.046 in the anisotropic approximation of atomic displacements using 1527F > 3σF. The idealized formula of ilyukhinite (Z = 3) is written as (H₃O,Na)₁₄Ca₆Mn₂Zr₃Si₂₆O₇₂(OH)₂ · 3H₂O. The new mineral differs from other representatives of the eudialyte group by the predominance of both oxonium in the N positions of extra-framework cations and manganese in the М2 position centering the tetragonal pyramid.     

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.     

Synthesis and characterization of 9-(4-nitrophenyl)3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-1,8(2H,5H) acridinedione and its methoxyphenyl derivative

9-(4-Nitrophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-1,8(2H,5H) acridinedione (NTHA) crystallizes in orthorhombic space group P2₁2₁2₁ with a = 5.9716(1) Å, b = 18.0476(3) Å, c = 19.2445(2) Å, V = 2074.04(5) ų, Z = 4, D_cal = 1.263 Mg m^?3 and R = 0.0521 (wR = 0.1326) for 4078 observed reflections. 9-(4-Nitrophenyl)-10-(4-methoxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-1,8(2H,5H) acridinedione NMTHA, crystallizes in monoclinic space group P2₁/c with a = 15.669(5) Å, b = 10.652(4) Å, c = 18.337(6) Å, β = 108.25(1)^°, V = 2906.66(2) ų, Z = 4, D_cal = 1.245 Mg m^?3 and R = 0.0725 (wR = 0.1847) for 5105 observed reflections. The experimental values are compared with the theoretical values calculated based on the semiemperical methods. The structures are stabilized by N–H?sO and C–H?sO types of intermolecular interactions in addition to van der Waals forces.     

Synthesis and structure of Cs[UO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)(OH)] · <Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O (<Emphasis Type="Italic">n</Emphasis> = 1.5 or 1)

The synthesis and single-crystal X-ray diffraction study of Cs[UO₂(SeO₄)(OH)] · 1.5H₂O (I) and Cs[UO₂(SeO₄)(OH)] · H₂O (II) are performed. Compound I crystallizes in the monoclinic crystal system, a = 7.2142(2) Å, b = 14.4942(4) Å, c = 8.9270(3) Å, β = 112.706(1)°, space group P2₁/m, Z = 4, and R = 0.0222. Compound II is monoclinic, a = 8.4549(2) Å, b = 11.5358(3) Å, c = 9.5565(2) Å, β = 113.273(1)°, space group P2₁/c, Z = 4, and R = 0.0219. The main structural units of crystals I and II are [UO₂(SeO₄)(OH)]^? layers which belong to the AT ³ M ² crystal chemical group of uranyl complexes (A = UO ₂ ²⁺ , T ³ = SeO₄ ^2?, and M ² = OH^?). In structure I, johannite-like layers are found. Structure II is a topological isomer of I. The two structures differ in the number of U(VI) atoms bound to the central atom by all bridging ligands.     

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.     

Calcio-olivine γ-Ca<Subscript>2</Subscript>SiO<Subscript>4</Subscript>: I. Rietveld refinement of the crystal structure

The structure of the natural mineral calcio-olivine (γ-Ca₂SiO₄) found in skarn xenoliths in the region of the Lakargi Mountain (North Caucasus, Kabardino-Balkaria, Russia) is refined by the Rietveld method [a = 5.07389(7) Å, b = 11.21128(14) Å, c = 6.75340(9) Å, V = 384.170(5) ų, Z = 4, ρ_calcd = 2.98 g/cm³, space group Pbnm]. The X-ray diffraction pattern of a powdered sample is recorded on a STOE STADI MP diffractometer [λCuK _α1; Ge(111) primary monochromator; 6.00° < 2θ < 100.88°; step width, 2.5° in 2θ; number of reflections, 224]. All calculations are performed with the WYRIET (version 3.3) software package. The structural model is refined in the anisotropic approximation to R _p = 6.44, R _wp = 8.52, R _exp = 5.85, R _B = 4.98, R _F = 6.90, and s = 1.46. It is shown that the sample under investigation is a mixture of several mineral phases, among which calcio-olivine (the natural analogue of the γ-Ca₂SiO₄ compound) (83%), hillebrandite (13%), and wadalite (4%) are dominant. Only the scale factors and the unit cell parameters are refined for hillebrandite Ca₂SiO₃(OH)₂ [a = 3.63472(16) Å, b = 16.4140(10) Å, c = 11.7914(8) Å, space group Cmc2₁, Z = 6] and wadalite Ca₆Al₅Si₂O₁₆Cl₃ (a = 12.0088 Å, space group, I \(\bar 4\)3d Z = 4). The results of the structure refinement of the main component of the sample confirm that the mineral calcio-olivine is isostructural to the synthetic compound γ-Ca₂SiO₄. The structure of this compound is formed by the heteropolyhedral framework composed of Ca octahedra joined together into olivine-like ribbons and isolated Si tetrahedra.     

Crystal structure of 2,4,6-trinitropyridine and its N-oxide

The structures of 2,4,6-trinitropyridine (TNPy) and its N-oxide were determined by X-ray single crystal diffraction. TNPy and 2,4,6-trinitropyridine-1-oxide (TNPyO) crystallize in space groupPbcn andPnma, respectively. The crystallographic parameters are as follows: TNPy,a = 28.573(6) Å,b = 9.7394(19) Å, andc = 8.7566(18) Å, α = β = γ = 90^°, μ = 0.164 mm^?1,V = 2436.8(8) ų,z = 12,Dx = 1.751 mg/mm³,F(000) = 1296,T = 293(2) K, 1.43^°≤ θ≤ 27.40^°, the finalR factor:R ₁ = 0.0574,wR ₂ = 0.1337. TNPyO,a = 9.6272(19) Å,b = 14.128(3) Å, andc = 5.9943(12) Å, α = β = γ = 90^°, μ = 0.179 mm^?1,V = 815.3(3)ų,z = 4,Dx = 1.875 mg/mm³,F(000) = 464,T = 293(2) K, 2.88^°≤ θ≤ 27.44^°, the finalR factor:R ₁ = 0.0497,wR ₂ = 0.1515.     

Crystal structure of centrosymmetric 12-layer sodium-rich eudialyte

The structure of a new representative of the eudialyte group with the formula (Na,Sr,K)₁₈Ca₆Zr₃Fe[Si₂₅O₇₂](OH)₂Cl · H₂O from the Lovozero massif (Kola Peninsula) was studied by X-ray diffraction. The trigonal unit-cell parameters are a = 14.226 Å, c = 30.339 Å, sp. gr. R \(\bar 3\) m; the R factor is 0.045 based on 990 reflections. This sample is of interest as a sodium-rich and iron-poor mineral having a rare centrosymmetric structure, in which the M(2) site is occupied predominantly by sodium atoms. The dependence of the formation of centrosymmetric and non-centrosymmetric structures on the composition of eudialyte-group minerals was analyzed.