Home – Home – Jornals – Contemporary Problems of Ecology 2009 number 3

New data on the age, composition, formation conditions, and ore-geochemical specialization of the Nui Chua layered peridotite-gabbro complex are reported. They evidence that the complex resulted from the Permo-Triassic mantle plume activity in northern Vietnam (southern framing of the Yangtze Platform). Two series of mafic and ultramafic rocks differing in ore productivity-layered (PGE-Cu-Ni) and pegmatoid (Fe-Ti-V)-have been recognized within the complex. The first estimates of the composition of their parental melts have been obtained.

Modal analysis, bulk-rock geochemistry and phase chemistry of sandstones of the Miocene Fat'ha and Injana formations, northern Iraq, show that the clastics were derived from heterogeneous sources that include basic igneous and metamorphic rocks as well as older sedimentary rocks. The sandstones are generally carbonate-rich lithic arenites. Their geochemistry supports the petrographic results and indicates that they are all Fe-rich, lithic or quartz arkosic sandstones. According to geochemical data, garnets are derived from metamorphic sources, hornblende is of igneous origin, and clinopyroxenes, are produced by basic igneous rocks. Epidote is most probably to be a product of disintegration of metamorphic rocks, essentially, metamorphosed igneous rocks. Rutile geochemistry implies low-grade metamorphic and basic to ultrabasic igneous sources. Chemical composition of chromian spinels indicates that they are derived from Alpine-type peridotite. The ophiolitic-radiolarite belts of Taurus-Zagros as well as the uplifted Cretaceous and Paleocene strata of north and northeastern Iraq are likely to be the major source of clastics to the Fat'ha-Injana basin, a foreland basin formed as a result of the continental Arabian and Turkish/Iranian plates collision.

We studied the typomorphic features of native gold in orebodies with veinlet-disseminated quartz-sulfide mineralization at the Degdekanskoe deposit localized in Permian black-shale strata of the Ayan-Yuryakh anticlinorium in the upper-Yana-Chukchi folded area. With a successive HF and HNO₃ dissolution of samples, the abundance of native gold intimately intergrown with sulfides (on the average, 42.1%) and carbonaceous substance was revealed. It is shown that most of its grains are small and fine (the <0.25 mm fraction averages 90.2%) and are accumulated mainly in interstices. Two gold generations have been revealed: low-medium-grade (751-840 ‰) (main) and high-grade (885-931 ‰). The zonal structure of mineralization has been established. The upper, most enriched horizons bear coarser-grained gold of the two generations, which are localized in both sulfide and silicate minerals. With depth, the total content of gold decreases, the share of sulfide gold increases, and the grain size and grade also diminish, with the low-medium-grade generation prevailing.

We studied the organochemical distribution of saturated hydrocarbons in organic matter of mudstones of the Vendian Marna Formation in the Sayan-adjacent Biryusa area. The formation is composed of glacial, glacio-alluvial, and lacustrine deposits.
In the fraction of saturated hydrocarbons in chloroform extracts (bitumoids), a homologous series of earlier unknown 2,7-dimethyl alkanes has been identified, with molecules having the even number of carbon atoms prevailing. The possible sources of such abundant biomarkers are considered.

We study earthquake-induced soft-sediment deformation (seismites) in reference Quaternary sections of southeastern Altai. Sediments in the sections bear signature of liquefaction and fluidization and deformation is localized in thin (few centimeters to 0.5-1.0 m) continuously striking and frequently repeated layers sandwiched between undeformed sediments. The soft-sediment deformation records coseismic motion of different slip geometries. Seismic origin is also inferred for layers and lenses of coarse colluvium slid into the lake bottom from the slopes, which intrude plane-bedded silt and sand and vary in thickness from a few centimeters to one meter. The occurrence of seismic soft-sediment deformation at different stratigraphic levels of the Quaternary and in the Upper Pliocene Beken Formation confirms the high seismicity of southeastern Altai in Quaternary time.

The paper presents data on Callovian foraminiferal assemblages from several wells in two localities of the West Siberian plain (Shaim oil and gas district, northwestern West Siberia, and Mykhpai field, central West Siberia). The assemblages are compared and studied in terms of space and time changes of their stratigraphy, which can make basis for a more detailed zonal subdivision as more data become available. The taxonomic compositions of the assemblages are summarized in tables for specific wells to highlight their geographic variations.

A nonsteady filtration theory combined with electromagnetism by means of common physical principles of hydrodynamic description of condensed media is constructed. Based on the linear version of the theory, an electromagnetic method for measuring ξ-potential is suggested.

We report the results of continuous temperature monitoring (812 days, from 28 June 2005 to 26 September 2007) in a 80 cm layer of peat soil in Bakchar bog (West Siberia), at sampling rates of 60 min in wintertime and 15 min in summertime. Both annual and daily temperature patterns are controlled by water table position and weather conditions. Wintertime soil temperature patterns are disturbed by the formation of a seasonal frozen layer with its thickness (freezing depth) depending on the time when steady snow cover sets up and on soil moisture. During the period of frozen layer thawing, the temperature of peat becomes sensitive to peat moisture and water table position as well as to the air and peat surface temperature. The warm-season soil temperature patterns bear effects of peat warming by rainwater percolation, both in night- and daytime. The patterns with soil warming during rainfall and phase change during seasonal freezing-thawing cycles record disturbances to conductive heat transfer.

Three-year-long investigation of the microflora in the soil of nut-fruit woods in the south of Kyrgyzstan showed a wide distribution of spore-forming bacteria B. subtilis, B. cereus, B. idosus, B. megaterium. In the complex of these bacteria, spore-forming bacteria B. thuringiensis are widespread. The occurrence of spore-forming bacteria B. thuringiensis in mountainous forest black-brown soils reached 80 % of soil samples. Dominating subspecies were tohokuensis (H17), israelensis (H14), toguchini (H31). Abundance of B. thuringiensis was insignificant and accounted for only 4 % of spore-forming bacteria. The abundance B. thuringiensis in oozy biocenoses on the banks of water bodies at the territory of Sary-Chelek reserve reached 12.6-18.0 % of soil spore-forming bacteria. In this connection, it is possible to assume that B. thuringiensis not only are conserved in soils but also can reproduce.

Interrelations between the data on the ecological state of water objects and results of their biological testing with the use of test objects from different groups (Paramecium caudatum and Chlorella vulgaris) are investigated. Statistically significant dependences between the results of bioinformation and physicochemical methods of the analysis of a pollution degree of surface water in the regions of hydrocarbon raw materials extraction are revealed.

A method of estimating the quality of habitats on the basis of field accounts with records of routes and the positions of tracks with the help of GPS, multi-channel survey Landsat, a three-dimensionаl model of the relief and discriminant anаlysis is demonstrated. For the analysis of the distribution of mink (American and European) as an example, we demonstrate the principles of choosing the optimal analysis method, revelation of environmental characteristics determining the distribution of the species, mapping, estimation of the quality of habitats and the probabilities to detect tracks. The outlooks and some problems of the implementation of the proposed approach are discussed.

On the basis of the proposed model, the basic parameters of number obtained by the areal count method are bound. The model is built on the basis of the regular changes of occurrence and abundance with changes of the area of a test ground. The procedure is applicable to the conditions of aggregated disposition of the counted individuals over a region under investigation.

Data on the specific features of the parasite-host links of gamasid mites of the genus Hirstionyssus Fonseca with small mammals in the south of the West Siberian Plain are reported.

Major features of the spatial nonuniformity of the oribatid mite population at the territory of North-Eastern Altay are revealed on the basis of the results of investigations carried out in 2002 and 2006. The dependence of changes in the population appearance on environmental factors is evaluated.

Ecological coenotic characterization of grass around the ant hills of Formica polyctena Foerst. situated within the boundaries of a fragmented forest compartment is presented. The composition of the myrmecotopical grass assembly is determined. Transformation into meadow and synanthropization of the grass cover at the territories adjacent to the nesting areas are revealed. A similarity between ant species F. aquilonia Yarr. and F. polyctenа in the transformation of the coenotic and morphological structure of grass at the territories adjacent to the nesting areas was noted.

Ant faunа of the Chuiskaya depression was determined to have 17 species; 4 of them inhabit the desert steppe, 8 - the near-water saline steppe, and 11 - the mountainside valley meadows and forests. Widespread in adjacent Mongolia and Tuva are 14 out of 17 registered species. This is an evidence of the high faunal community of these territories. The population pattern of ants is determined by two species with extremely low number (up to 0.01 nest/100 m²), Proformica mongolica Ruzsky and Cataglyphis aenescens Nylander; Formica subpilosa Ruzsky joins them in the hollows. Two zones of higher number were revealed in the vertical direction - on the southern slopes of the high-mountain desert steppes (basin of the Yustyd river) and alkaline biotopes of the Chuya river flood-lands.

The molecular structure of tris-hexafluoroacetylacetonates of dysprosium, holmium, erbium, and ytterbium (M(hfa)₃, M = Dy, Ho, Er, Yb) is studied in the framework of synchronous electron diffraction and mass-spectrometric experiment and also quantum-chemically. For all M(hfa)₃ complexes structural parameters r_a, r_g, and r_h1 are found. It is established that the coordination polyhedron LnO₆ has a configuration of D₃ symmetry. In experiments on superheated vapors of Dy(hfa)₃, Ho(hfa)₃, and Yb(hfa)₃ the molecular forms present in the vapor at different degrees of superheat are determined.

The IR spectra of α-glycylglycine (H₃⁺N-CH₂-CO-NH-CH₂-COO^-) are studied in the temperature range of 93 to 413 K. Changes in the spectra due to temperature variation are correlated with the previously obtained X-ray diffraction data on anisotropic compression of the structure and changes in the parameters of hydrogen bonding. Changes in the vibrational frequencies of NH⁺₃ and COO groups in the IR spectrum of α-glycylglycine are compared to changes in the vibrational frequencies of the same groups in the IR spectra of polymorphs of glycine, L- and DL-serine.

A study of the IR spectra of L- and DL-cysteine is carried out in a range of frequencies from 4000 cm^-1 to 600 cm^-1 and temperatures from 333 K to 83 K. Changes in the spectra of L- and DL-cysteine (NH⁺₃-CH(CH₂SH)-COO^-) on cooling are analyzed in comparison with the spectra of L- and DL-serine (NH⁺₃-CH(CH₂OH)-COO^-) and three polymorphs of glycine (NH⁺₃-CH₂-COO^-) previously studied under temperature variation. Changes in the IR spectrа at variable temperatures are correlated with previously obtained diffraction data on anisotropic compression of the structure and changes in the geometric parameters of hydrogen bonds. Special attention is paid to temperature regions in which anomalies were detected by vibrational spectroscopy, X-ray diffraction, and calorimetry.

By means of IR spectroscopy with the use of factor group analysis for vibrations of the B-O bond, rare-earth borates with a general formula of RM₃(BO₃)₄ (R is Nd, Gd, and Y; M is Al, Ga, Cr, and Fe) and related polytypic structures are assigned to space groups R32 or С2/c. Compounds with both almost homogeneous structures and with inclusions of the monoclinic polytype are revealed among rhombohedral borates. The latter is most typical of phases with a small octahedral Al cation. It is shown that in the monoclinic modification of NdAl and NdCr borates fragments of the rhombohedral phase are always present. Alternation of differently ordered structural fragments is determined by temperature conditions of crystallization.

NMR (¹⁹F, ¹H) methods are used to study ionic mobility in heptafluorozirconate (NH₄)_2.4Rb_0.6ZrF₇ in a range of temperatures from 150 K to 430 K. Types of ionic movements are determined, and their activation energy is evaluated. As a result of a phase transition a modification forms in which diffusion in the ammonium sublattice and isotropic reorientations of ZrF^3-₇ complex anions are observed. According to preliminary data, due to diffusion of ammonium ions the compound has relatively high ionic conductivity (σ ≈ 8.3×10^-5 S/cm at 423 K).

The complex [Pd(bipy)Cl₂] (1) (bipy = 2,2′-bipyridyl) has been synthesized and characterized by NMR spectroscopy, elemental analysis and X-ray diffraction method. The first step hydrolysis reaction kinetics for the complex was studied by UV-absorption spectroscopy; the speed constant (k₁) was found to be 3.0×10^-4 s^-1. The fluorescence spectra have been collected to investigate the interaction of complex (1) with fish sperm DNA (FS-DNA) and the results indicate that the complex (1) has an effective intercalation within DNA. The reaction of complex (1) with adenine in ethanol/water results in the compound [Pd₂(bipy)₂(ade)₂]Cl₂⋅3H₂O (2) (ade = adenine) whose crystal structure was determined by X-ray diffraction method. The structure is orthorhombic, Pmmn, a = 12.993(4), b = 14.512(5), c = 9.837(3) Å, V =
1854.8(11) ų, Z = 2 (C₃₀H₃₀Cl₂N₁₄O₃Pd₂), final R₁ = 0.0675. The palladium complex is a binuclear cation, where two ade ligands bridge two Pd(II) centers, while each Pd(II) is also chelated by one bipy ligand.

Nature of the kinematic shear viscosity of water ν is discussed in the work. Dependences of ν on temperature t, reduced volume ν, and the average number of hydrogen bonds per one molecule n_H (t =
T/T_c, = T_c and are critical values of temperature and reduced volume) are analyzed in detail on a liquid-vapor coexistence curve. It is shown that at T < T_H (T_H ≈ 310 K is the characteristic temperature of water) the formation of the kinematic shear viscosity is induced by activation. At T > T_H, the shear viscosity of water is the sum of two contributions. One of them is of the same nature as in simple liquids, and another is caused by effects of hydrogen bonds. The temperature dependence of ν in this temperature region has nothing in common with exponential formulas of activation theory. The explicit form of the functional dependence of the kinematic shear viscosity on t, , and _νn_H is found and substantiated. It is shown that the value and temperature dependence of n_H resulting in the experimental values of the kinematic shear viscosity of water agree well with the values corresponding to density and evaporation heat data.

Crystals of Y_0.90Tb_0.10Ba₂Cu₃O_6.75 have been prepared by spontaneous crystallization from slowly cooled non-stoichiometric melt of the system Y-Tb-Ba-Cu-O. Average size of platelet crystals having mirror surface is 2×2, the largest - 8×9 mm with thickness 0.1-0.2 mm. The crystals have been characterized by powder X-ray diffraction and electron microprobe analysis. Tetragonal symmetry of the crystals has been determined by X-ray diffraction. Magnetic susceptibility measurements have revealed that the crystals manifest transition to superconducting state without additional annealing (Т_с = 60 K). Structures and compositions - Y/Tb ratio (σ = 0.01) and oxygen content (σ = 0.04) - have been refined for two single crystals. Possibility of rhombic distortion of the tetragonal symmetry is discussed.

Crystals of LuBaCo₄O_7+δ (114Lu) have been obtained by spontaneous crystallization of slowly cooled non-stoichiometric melt of the system Lu-Ba-Co-O. The crystals have been characterized by EDX microprobe and synchrotron radiation powder diffraction. Structure refinement has been carried out (automated diffractometer Bruker X8 APEX with a CCD detector, МоK_α, graphite monochromator, θ_max = 32.54°). Parameters of the hexagonal unit cell: space group P6₃mc, a = 6.2601(1) Å, c = 10.2017(3) Å, V =
346.23(1) ų, Z = 2, d_calc = 6.331 g/cm³. Framework structure of the wurtzite type has been refined anisotropically to R-factor 0.0174. Charge balance in the compound and geometrical matching of structural fragments are discussed.

In the present study high-temperature X-ray diffraction, thermal analysis, and mass-spectrometry have been employed for investigation of samples in the La_1-xSr_xFeO_3-δ family (0 ≤ x ≤ 1), the materials being solid solutions having perovskite structure. It has been shown that the loss of oxygen by the samples on heating to 1200°C in air (0 ≤ x ≤ 1) or in vacuum (х < 0.75) does not result in structural rearrangement of the solid solutions, but causes an increase in the lattice parameters. Heating of the compositions with x ≥ 0.75 in vacuum affords phases with ordered vacancies. The observed structural evolutions (growth of the unit cell parameter and vacancy ordering) are reversible, and on re-oxidation (on cooling in air or additional heating of the "vacuum" samples in air atmosphere) the original parameters of the oxides are recovered. The amount of oxygen evolved on heating increases in vacuum or in helium atmosphere, as compared to air, and also grows with rising strontium content, but under experimental conditions does not reach the maximum possible value (δ = x/2).

A solvate [Cu(CF₃COCHCOCH₃)₂(CH₃COCH₃)] has been synthesized and characterized for the first time. According to X-ray structural data (diffractometer X8 APEX BRUKER, radiation MoK_α, T = 150 K), it crystallizes in the monoclinic crystal system, space group P2₁/c, a = 8.9940(4) Å, b = 22.3966(11) Å, c = 8.1884(3) Å, β = 92.705(2)°, V = 1647.59(12) ų, Z = 4, d_calc = 1.725 g/cm³, final R = 0.0272. The structure is molecular. In the equatorial plane the atom Cu(II) is surrounded with four oxygen atoms of two chelating ligands (CF₃COCHCOCH₃)^-; Cu-O distances 1.927-1.937 Å, O-Cu-O angles 86.18-93.30° and 170.18-175.67°. Square coordination of Cu is complemented to the square-pyramidal one by the oxygen atom of an acetone molecule behaving as an axial ligand; Cu-O_acetone 2.342 Å, O-Cu-O_acetone 89.66-100.11°. In the studied compound disorder of one of the chelate ligands implies the co-existance of the molecules in the cis- and trans-configuration in the crystal under ratio 54.6:45.4. In air the solvate rapidly degrades losing acetone, while in a sealed vessel melts around 313 K. Temperature dependence of equilibrium vapor pressure of acetone over the complex was measured with the static spoon gauge technique, thermodynamic characteristics of its dissociation process being derived: [Cu(CF₃COCHCOCH₃)₂(CH₃COCH₃)]_s = [Cu(CF₃COCHCOCH₃)₂]_s + CH₃COCH_3g, ΔH = 49.6(3) kJ/mol, ΔS = 152(1) J/(mol K), ΔG = 4.30(2) kJ/mol.

A DTA study of thermal decomposition of (NH₄)₂[Ru(NO)Cl₅] in helium atmosphere has been carried out, a synthetic procedure for preparation of the trans-diammine complex mer-[Ru(NO)(NH₃)₂Cl₃] (I) with yield ~70% has been developed. On re-crystallization of I from aqueous solution a trans-aquanitroso complex [Ru(NO)(NH₃)₂Cl₂(H₂O)]Cl⋅H₂O (II) has been isolated. The structures of the compounds have been determined by single crystal X-ray diffraction: space group Pbcn, a = 6.607(1) Å, b = 11.255(2) Å, c = 9.878(2) Å (I) and space group Ima2, a = 8.3032(3) Å, b = 8.0890(2) Å, c = 15.9192(5) Å (II).

Synthesis and single crystal X-ray diffraction study of hafnium(IV) dipivaloylmethanate Hf(dpm)₄ and chloro-tris-(dipivaloylmethanato)hafnium(IV) Hf(dpm)₃Cl have been carried out. Crystal data: a =
22.6606(5) Å, b = 11.3990(4) Å, c = 19.8513(7) Å, β = 106.458(1)°, Рс, Z = 4, d_calc = 1.231 g/cm³, R = 0.075 for C₄₄H₇₆HfO₈; a = 10.6376(13) Å, b = 10.6701(10) Å, c = 19.4400(22) Å, α = 74.970(3)°, β = 75.672(3)°, γ = 61.725(2)°, P-1, Z = 2, d_calc = 1.366 g/cm³, R = 0.031 for C₃₃H₅₇ClHfO₆. The structures are molecular and are built from discrete mononuclear complexes joined by van der Waals interactions. Disordering of carbon atoms preserving at low temperature is observed for the compound Hf(dpm)₄. It has been found out that the structure contains two crystallographically unique complexes of hafnium(IV) with central atoms coordinated with eight oxygen atoms of four dipivaloylmethane ligands, bond lengths Hf-O fall within 2.084-2.222 Å, the distances Hf…Hf between the molecules are 10.07-13.87 Å. In Hf(dpm)₃Cl the hafnium atom is seven-coordinated with six oxygen atoms of three β-diketonate ligands and one chlorine atom, the distances Hf-O fall within 2.087-2.179 Å, the lengths of the bond Hf-Cl for two crystallographically independent molecules Hf(1) and Hf(2) are 2.466 Å and 2.442 Å, respectively.

Molecular and crystal structures of a new complex compound of copper(II) with 3-methyl-5-carboxylatopyrazole (СН₃PzCOO^-) with the composition Cu(СН₃PzCOO)₂⋅H₂O have been determined by single crystal XRD. It has been demonstrated that the carboxylate ion performs the bridging tridentate function. In the equatorial plane coordination occurs through the pyridine N atom of the pyrazole and one of O atoms of the carboxylate group yielding a five-membered metallocycle CuNOC₂. The second О atom of one of the ligands is bound to the neighboring copper(II) ion affording an infinite linear chain. The coordination polyhedron of the copper atom is a square pyramid, coordination core CuN₂O₃.

Results of a quantum-chemical study of the molecular structure of dimerization products of saturated 1,3-butadiene and hexafluoro-1,3-butadiene (tricyclo[3.3.0.0^2.6]octane, dodecafluorotricyclo[4.2.0.0^2.5]octane (I), and dodecafluorotricyclo[3.3.0.0^2.6]octane (II)) are presented. The calculated symmetry of the molecule of I in vacuum (C₂) differs from its symmetry in the single crystal (C_i, XRD). The most stable of dimers (II) contains C-C bonds with a length of up to 1.573 Å and a four-atom cycle with angles of 82.3°.

Formalism is developed in which contributions of binary and ternary interactions towards free energy of a mixture of low-spin (A) and high-spin (B) isomers of spin crossover compounds as well as effects of ordering are taken into account. Parameters characterising non-ideality in this formalism are the excess free energy (ΔF_ex) and absolute asymmetries (Δ^A, Δ^B) of splittings of free energy levels. The excess free energy characterises the effects of binary interactions whereas asymmetries arise from ternary interactions. According to this model, the plateau in the spin crossover transition curve originates from the phenomenon of ordering taken into account in the Gorsky-Bragg-Williams approximation.

Considering many-body interactions in tetrahedral structures as perturbations of binary potentials by third bodies yields a free energy functional of the binary mixture equivalent to one earlier derived for spin crossover equilibrium in one-dimensional chains. Formal non-ideality parameters of this functional, the excess energy and asymmetries of splittings can be expressed in terms of molecular parameters based on binary potentials.

Chemical shifts (c.s.) of ¹Н nuclei in methanol are measured for methanol-benzene and methanol-phenanthrene systems. A method to determine the equilibrium constant of the molecular association reaction by NMR spectroscopy data is proposed for systems with low solubility of a compound when the dependence of c.s. on the composition is close to a straight line. The equilibrium constants for the formation of molecular complexes in methanol-benzene and methanol-phenanthrene systems are found.

The substitution reaction of thiocyanide groups of the complex K₄[Nb₆F₆Br₆(NCS)₆] in aqueous hydrochloric acid has afforded a new fluoride cluster anion [Nb₆FBrCl(H₂O)]^2- isolated as the salt (Me₄N)₂[Nb₆F₆Br₆Cl₄(H₂O)₂]⋅6H₂O (space group R3m, a = 11.230(5) Å, c = 26.230(5) Å, V = 2865(2) ų, Z = 3, R1 = 0.0362, R2w = 0.0886). The anion contains the cluster core Nb₆F₆Br₆ having ordered "inner" ligands. Difference in the atomic radii of "inner" ligands causes a significant distortion of the metal cluster along the three-fold axis.

The structure of the salt Cs[Gd(H₂O)₄Re₆Te₈(CN)₆]⋅4H₂O (space group P-1, a = 9.436(5) Å, b =
12.365(7) Å, c = 15.187(8) Å, α = 89.104(10)°, β = 86.996(10)°, γ = 82.304(9)°) has been established by single crystal XRD. The structure of the compound features layers involving Gd³⁺ cations bound to cluster anions [Re₆Te₈(CN)₆]^4- through cyanide groups. The interlayer space contains cesium cations and crystallization water molecules.

Supramolecular H-bonded complexes formed between p-ethoxybenzoic acid and 4,4′-dipyridyl or N,N′-dipyridylpiperazine were obtained as nematic liquid-crystalline phases. The corresponding crystals suitable for single crystal X-ray analysis were isolated and investigated. The stoichiomtery of complex 1 is (4,4′-dipyridyl)⋅2(p-ethoxybenzoic acid) and that of complex 2 is (N,N′-dipyridylpiperazine)⋅2(p-ethoxybenzoic acid). The molecular packing observed in the crystal structures investigated indicates that the mesogenic phases of the complexes are induced by H-bond interactions.

The structure of 8-carboxy-18-chloro-14-hydroxy-20-isopropyl-16-methoxy-4,8-dimethyl-15-oxaocta-
cyclo[11.7.1.0^3,120^4,90^12,190^14,180^16,210^17,20]henicosane has been determined by single crystal X-ray diffraction.

The products of the reaction of 2-alkenylthiopyridines with mercury iodide have been studied by single crystal X-ray diffraction. It has been demonstrated that the products are organomercury derivatives of salts of 2,3-dihydrothiazolo[3,2-a]pyridinium.

Benzyltriphenylphosphonium trans-tetrachloro(methanol)oxomolybdate(V) has been obtained from methanol suspension of benzyltriphenylphosphonium molybdate(VI) saturated with hydrogen chloride. The crystal structure comprises discrete trans-tetrachloro(methanol)oxomolybdate(V) anions and benzyltriphenylphosphonium cations. The anion has distorted octahedral geometry of central atom with visible trans influence imposed by short Mo-O bond (1.659(2) Å). The methanol O atom is bonded to the Mo atom, the bond being mostly electrostatic in character. A comparison with previously reported structures indicates that the methanol methyl moiety can switch between different positions with respect to the chloride ligands.