Novel Cyanide-Bridged Three-Dimensional Coordination Polymer Derived from an Octahedral Rhenium Cluster [Re6Te8(CN)6]4?: Synthesis and Crystal Structure of [{Mn(H2O)2(DMF)} 2Re6Te8(CN)6]·2H2O

The reaction of a water solution of K₄Re₆Te₈(CN)₆ with a solution of Mn(NO₃)₂ in 0.02M hydrochloric acid in the presence of DMF gave crystals of a cluster rhenium complex [{ Mn(H₂O)₂(DMF)}₂Re₆Te₈(CN)₆]·2H₂O. The structure of the compound was determined by single crystal X-ray diffraction (a = 12.6679(9) Å, b = 17.4524(12) Å, c = 9.7882(6) Å, β = 105.570(6)°, V = 2084.6(3) ų, Z = 2, space group P2₁/n, R = 0. 0389). In the complex, the [Re₆Te₈(CN)₆]⁴⁻ cluster anions are linked to Mn²⁺ cations by the cyanide bridges, the manganese cations being additionally coordinated by the DMF molecule and two water molecules. The neighboring clusters are joined by Re-C-N-Mn bridges into a three-dimensional framework possessing cavities filled with doubly disordered water molecules.Original Russian Text Copyright © 2004 by Yu. V. Mironov, S. F. Solodovnikov, V. E. Fedorov, and Yu. V. Gatilov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 918–922, September–October, 2004.     

New Phase in the Bi–Sr–Ca–Cu–O System

Cooling a melt of a Bi–Sr–Ca–Cu–O system (Bi:Sr:Ca:Cu = 4:3:3:4 or 2:2:2:4) from 1000°C-1050°C yielded crystals of a new red-colored nonsuperconducting phase, accompanying the superconducting 2212 and 2201 phases. Based on the EPR spectra, it was concluded that copper is univalent in this compound. The new phase has a composition Bi_2.2Sr_1.6Ca_1.3Cu₂Ox. The X-ray diffraction pattern has been indexed, and the unit cell parameters of the phase have been determined: space group P2/m, a = 12.93, b = 4.55, c = 10.94 ; = 102.72°.     

Transport of charged particle pulses in interplanetary magnetic fields

The charged particle scattering in the presence of a regular magnetic field is considered starting from the Boltzmann kinetic equation in the case of an arbitrary relation between the mean free path and the distance from a particle source. It is shown that the Green function for the kinetic equation can be represented as the sum of the distribution functions of non-scattered particles which propagate with the injection pitch angle and of the scattered ones. The obtained Green function of the Boltzmann equation and also the particle density describe the space-time-pitch angle cosmic ray distribution that corresponds to an instantaneous particle injection at a particular pitch angle.This work was supported by International Science Foundation (grant N UC 8000) and by Slovak Grant Agency for Science (grant No. 1353/95).     

Synthesis and crystal structure of Nb2S4(S2NCEt2)4, the first molecular complex containing an [Nb2(μ2-S2)2]4+ fragment

The crystal structure was determined for Nb₂S₄(S₂NCEt₂)₄ obtained in 48% yield by the reaction of Cs₄Nb₂S₄(NCS)₈ with NaS₂CNEt₂ in water: a=21.181(8), b=6.958(1), c=16.623(6) Å, =133.95(2)^o, V = 1764(1) ų, space group C2/m, Z=2, d_calc=1.708 g/cm³. The measurements were carried out on a Syntex P2₁ diffractometer with CuK radiation. A total of 2536 reflections were measured, of which 990 were used, R_aniso=0.0444. The basic fragment in this molecule is [Nb₂(₂–S₂)₂]⁴⁺, the Nb–Nb distance in which corresponds to a metal-metal single bond. The molecule is partially disordered over two positions about the twofold axis and mirror plane of the C2/m space group. The dithiocarbamate and disulfide ligands with bidentate coordination form a distorted square antiprism about each of the niobium atoms as in NbS₂Cl₂. The anomalously large S–S bond length in the S₂ ligand [2.282(5) Å] may be attributed to inaccuracy in the determination due to disorder.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 2, pp. 134–138, March–April, 1993.     

Influence of electronic and steric effects and hydrogen bonding on1H and13C spectral parameters in azo compounds

V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences; Turin University, Turin, Italy. Translated from Zhurnal Strukturnoi Khimii, Vol. 33, No. 6, pp. 91–101, November–December, 1992.     

Nonvalent interactions in the crystal structures of (Et4N)2[Mo3S7Br6] and (Et4N)(H9O4)[Mo3S7Cl6] clusters

Crystal structures of (Et₄N)₂[Mo₃S₇Br₆] (I) and (Et₄N)(H₉O₄)[Mo₃S₇Cl₆] (II) clusters belonging to the class of Mo₃S ₇ ⁴⁺ were determined by X-ray diffraction analysis. Crystals I are orthorhombic a=19.106(3), b=12.930(2), c=29.887(5) Å, V=7383(2) ų, space group Pbca, Z=8, d_calc=2.253 g/cm³, R(F)=0.0402, wR(F²)=0.0587 for 2493 F_hkl>4σ. Crystals II are monoclinic, a=17.106(3), b=18.882(4), c=11.006(2), Å, β=126.13(3)°, V=2871.2(9) ų, space group Cc, Z=4, d_calc=2.147 g/cm³, R(F)=0.0181, wR(F²)=0.0445 for 2307 F_hkl>4σ. Structure I has an anion dimer with 3S_ax…Cl=3.258(4)–3.404(4) Å; the dimer is similar to that observed in the structures of A₂[M₃X₇Hal₆], A=Ph₄P⁺, Ph₃EtP⁺, and PPN⁺. In structure II, infinite chains of anions bonded by 3S_ax…Cl contacts of 3.183(3)–3.394(3) Å were found. A similar phenomenon was established earlier for the structure of (Et₄N)(H₉O₄)[Mo₃S₇Br₆] (III), which is not isostructural to II. Compounds II and III also differ in the structure of the H₉O₄ ⁺ cation: infinite helix in II and pyramid in III.     

Avarol and isoavarol from a Pacific Ocean sponge Dysidea sp.

Two hydroquinone-group-containing terpenoids have been isolated from a Pacific Ocean spongeDysidia, sp. One of them has been identified by physicochemical methods as the previously known avarol. The second, isoavarol, obtained for the first time, differs from avarol by the 4(11)-position of the double bond.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, USSR Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 358–361, May–June, 1990.     

Adsorption of benzene on the V2O5/γ-Al2O3 catalyst

Adsorption of benzene on the V₂O₅/-Al₂O₃ catalysts was studied in the temperature interval from 443 to 493 K and at partial pressures of the adsorbate ranging from 1 to 400 Pa. The adsorption isotherms were plotted. The isosteric heats and various entropy characteristics of adsorption were determined. Mobility of benzene in the adsorption layer is restricted compared to the model of ideal dimeric gas. The adsorbed amounts of benzene and chlorobenzene are compared.