Reaction of H2PtCl6 with 18-crown-6 and dibenzo-18-crown-6 in 1,2-dichloroethane and acetonitrile

Compounds of the compositions [2(18-crown-6)6(H₂O)2(C₂H₄Cl₂){Pt²⁺(C₂H₄)}(Pt₂Cl₁₀)^2–], [4(18-crown-6)2(OH₃)⁺2(OH₂)2(NH₃)(Pt₂Cl₁₀)^2–], [(dibenzo-18-crown-6)6(H₂O){Pt²⁺(C₂H₄)}(Pt₂Cl₁₀)^2–], and [4(dibenzo-18-crown-6)2(OH₃)⁺2(OH₂)2(NH₃)Pt₂Cl₁₀)^2–] were prepared by reactions of H₂PtCl₆ with 18-crown-6 and dibenzo-18-crown-6.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1593–1599.Original Russian Text Copyright © 2004 by Guseva, Busygina, Khasanshin, Polovnyak, Yarkova, Yusupov.This revised version was published online in April 2005 with a corrected cover date.     

Gold(I) Pyrazolate Clusters: The Structure and Luminescence of the Tetranuclear, Base-Stabilized [(dppm)2Au4(3,5-Ph2Pz)2](NO3)2 ⋅ H2O

The tetranuclear Au(I) pyrazolate complex, [(dppm)₂Au₄(3,5-Ph₂Pz)₂](NO₃)₂  H₂O, 1, has been synthesized and structurally characterized. It is the first tetranuclear pyrazolate of Au(I) to have been found, although the trinuclear pyrazolates of Au(I) are well known. Complex 1 exhibits luminescence at 77 K when excited at 333 nm with an emission maximum at 454 nm. The emission has been assigned to ligand to metal charge transfer, LMCT, based upon the vibronic structure that is observed. The complex crystallizes in the monoclinic space group P2₁/c, with a=19.33(3) Å, b=20.26(3) Å, c=19.80(3) Å, =106.74(2)°, V=7425(17) ų, Z=8, and R=0.058. The Au    Au distances are Au(1)    Au(4)=3.185(3) Å, Au(1)    Au(2)=3.230(3) Å, Au(2)    Au(3)=3.079(3) Å, and Au(3)    Au(4)=3.280(3) Å.     

Crystal Structure of [Co?6H2O][Co?4H2O?2Gly]?2SO4

The crystals of [Co6H₂O][Co4H₂O2Gly]2SO₄ were studied by X-ray diffraction analysis (triclinic, P , a = 5.975(5), b = 15.469(5), c = 6.765(5) , =120.71(5), =83.23(5), =98.77(5)°). The structure contains complex cations of two types: [Co6H₂O]²⁺ and [Co4H₂O2Gly]²⁺ and SO ₄ ^2– anions linked by hydrogen bonds and electrostatic forces. Three chemically nonequivalent charged layers can be distinguished in the structure: one layer is formed by cobalt hexaaqua complexes, another by [Co4H₂O2Gly]^2– complexes, and the third layer consists of sulfate anions interlaying the former two. The layers alternate along the b axis and are connected by a 3D system of hydrogen bonds.     

An Inorganic-Organic Hybrid Supramolecular Hydrogen-Bonding and π-π Stacking Network Containing Ge4S4− 10 Cluster: Synthesis and Characterization of (H2bipy)2Ge4S10⋅(bipy)⋅7H2O (bipy=4,4′-bipy)

The reactions of TMA₄Ge₄S₁₀ (TMA=tetramethylammonium), Cu(NO₃)₂3H₂Oand 4,4-bipy under hydrothermal environment result in the formation of (H₂bipy)₂Ge₄S₁₀(bipy)7H₂O (1), which has been structurally characterized by single crystal X-ray analysis. The 3-D structure of 1 can be viewed as an inorganic-organic hybrid supramolecular hydrogen-bonding (hydrogen bonds: O–HO, N–HN, C–HO, N–HO, and O–HS) and - stacking network containing Ge₄S^4– ₁₀ clusters and novel [H₂bipybipyH₂bipy] trimers.     

Synthesis and X-Ray Crystal Structure Study of ]2-Methyl-4-(2-methylbenzoyl)-phenoxy] Acetic Acid Hydrazide

Benzophenone analog 3 has been synthesized and characterized by the X-ray diffraction (XRD) method. The compound crystallizes in a monoclinic space group P2₁/c with cell parameters a = 7.701(8) Å, b = 7.151(5) Å, c= 28.323(3) Å, = 104.639(4)°, Z = 4. The structure exhibits intra- and intermolecular hydrogen bonding of the type N–HO, C–HO, and N–HN. The molecules are interlinked through hydrogen bonds forming an infinite chain. This polymeric-like structure may play an important role in biological activity.     

Chiral coordination polymers based on Re cluster complexes,Cu<Superscript>2+</Superscript> cations,and 1,2<Emphasis Type="Italic">S</Emphasis>,3<Emphasis Type="Italic">S</Emphasis>,4-tetraaminobutane

Reactions of octahedral and tetrahedral chalcocyanide cluster complexes of Re with Cu²⁺ cations and 1,2S,3S,4-tetraaminobutane (Threo-tab) were used to synthesize and study the structures of the following six novel chiral complexes: [{Cu₂(NH₃)(Threo-tab)₃}Re₆S₈(CN)₆] 3H₂O (I) (where Threo is 1,2S,3S,4-tetraaminobutane), [{Cu₂(NH₃)(Threo-tab)₃}Re₆Se₈(CN)₆] 2H₂O (II), [{Cu(Threo-tab)}₂Re₆Te₈(CN)₆] 13.5H₂O (III), [{Cu(Threo-tab)}₂Re₄Te₄(CN)₁₂] 6.5H₂O (IV), [{Cu₂(NH₃)(Threo-tab)₂}Re₄Te₄(CN)₁₂] 4H₂O (V), and [{Cu(NH₃)(Threo-tab)}]₂[Re₄S_3.4Te_0.6(CN)₁₂] 1.25H₂O (VI). The structures of complexes I–IV contain extended channels of sufficiently large size capable of including guest molecules.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 4, 2005, pp. 289–301.Original Russian Text Copyright © 2005 by Mironov, Naumov, Brylev, Efremova, Fedorov, Hegetschweiler.     

Redox reactions of disulfiram: a pulse-radiolysis study

Redox reactions of disulfiram (DSF) were studied in aqueous solutions using the pulse-radiolysis technique. Reactions of DSF with one-electron oxidants Br₂ ^- and N₃, generated pulse radiolytically in aqueous solution at pH 7, yielded a transient (_max = 480 nm) which exhibited the characteristics of a disulphide cation radical and decayed by second-order kinetics. Reactions of DSF with halogenated peroxyl radicals CCl₃O₂, CHCl₂O₂, CH₂ClO₂ and CBr₃O₂ led to the formation of an adduct absorbing at 580 nm. The reduction potential was estimated to be 1.24 ± 0.06 V vs. NHE.     

Two-Dimensional Supramolecular from the Self-Assembly of Dissymmetrical Oxamidato-Bridged Heterometallic Trinuclear Building Blocks: Synthesis, Crystal Structure, and Magnetic Properties

Two heterometallic trinuclear complexes {[Cu(oxbp)]₂Co(H₂O)₂}1.5DMF0.5H₂O (complex 1) and {[Cu(oxbm)]₂Co(H₂O)₂}2DMF (complex 2) were obtained from the self-organization of two new dissymmetrical oxamidato-bridged copper(II) building blocks [Cu(oxbp)]^– and [Cu(oxbm)]^–[H₃oxbp=N-benzoato-N'-(3-aminopropyl)oxamido, H₃oxbm=N-benzoato-N'-(2-amino-2-methylethyl)oxamido, DMF=dimethylformamide]. The crystal structure of complex 1 has been determined. Complex 1 crystallize in triclinic system, space group P-1, a=8.0609(16) Å, b=10.661(2) Å, c=22.279(5) Å, =85.32(3), =86.64(3), =70.90(3), and Z=1. The crystal structure of complex 1 consists of neutral trinuclear complex units, and hydrogen bond involved DMF and water molecules. Through the hydrogen bonds, weak coordination and CuCu weak interactions, complex 1 features a 2-D supramolecular structure. Magnetic susceptibility measurements (5–100 K) indicate that the central Co(II) and terminal copper metal ions are antiferromagnetically coupled with J=–28.09 and J=–29.70 cm^–1 for complex 1 and 2, respectively.     

Mechanisms of Heterogeneous Processes in the System SiO2 + CH4: III. Products of >Si

Permenov  D. G.  Radzig  V. A. 《Kinetics and Catalysis》2004,45(2):273-278

ESR Spectra of Trifluoromethyl Radical Obtained by Radiolysis and Photolysis in Solid Matrices

The ESR spectrum of CF₃ radicals trapped at 77 K in glassy matrices of a hexafluoropropylene trimer was examined. All the anisotropic components of the spectrum were assigned. The signals from parallel and perpendicular components resulting from hyperfine coupling to fluorine nuclei in the axially symmetrical CF₃ radical were identified. The values of magnetic parameters were found to be A _|| = 25.15 mT, A = 9.1 mT, g _|| = 1.9996, and g = 2.0056. The computer simulated ESR spectrum of CF₃ radical obtained in a glassy hexafluoropropylene trimer matrix can be used to interpret the spectrum of this radical in other solid matrices. Available literature data on the ESR spectra of CF₃ radicals trapped in solid matrices are summarized.     

Unicyclic Graphs with Minimal Energy

If G is a graph and ₁,₂,..., _n are its eigenvalues, then the energy of G is defined as E(G)=|₁|+|₂|++| _n |. Let S _n ³ be the graph obtained from the star graph with n vertices by adding an edge. In this paper we prove that S _n ³ is the unique minimal energy graph among all unicyclic graphs with n vertices (n6).     

Gold(I) Formamidinate Clusters: The Structure, Luminescence, and Electrochemistry of the Tetranuclear, Base-Free [Au4(ArNC(H)NAr)4]

The structures of the tetragold(I) formamidinate cluster complexes, [Au₄(ArNC(H)NAr)₄], Ar=C₆H₄-4-OMe (1), C₆H₃-3,5-Cl (2), C₆H₄-4-Me (3), have been characterized by x-ray crystallography. The range of AuAu distances is 2.8–3.0 Å. The angles at AuAuAu are acute and obtuse 70 and 109°, 88 and 91°, and 63 and 116° in 1, 2, and 3, respectively. The four gold atoms are located at the corner of a rhomboid with the formamidinate ligands bridged above and below the near plane of the four Au(I) atoms. The tetranuclear gold(I) complexes show a bright blue-green luminescence under UV light, with an emission at 490 nm and a weak emission at 530 nm in the solid state, at room temp and 77 K. The oxidation of the formamidinate cluster, 1, has been studied electrochemically in 0.1 M Bu₄NPF₆/CH₂Cl₂ at a Pt working electrode with different scan rates. Three waves were obtained, 0.75, 0.95, and 1.09V vs. Ag/AgCl at a scan rate of 500 mV/s, the three waves are reversible. The potentials are independent of the scan rate in the range 50 mV/s to 3 V/s. The current at the third wave is larger than those at the first two.     

Crystal structure of 1-(2-pyridiniomethyl)-2,4-<Emphasis Type="Italic">bis</Emphasis>(phenylsulfonyl)benzene bromide

The crystal structure of 1-(2-pyridiniomethyl)-2,4-bis(phenylsulfonyl)benzene bromide, (C₂₄H₂₀NO₄S₂)⁺. Br^– (I) has been investigated by X-ray diffraction (XRD)analysis. The triclinic structure of I (space group P1, a = 7.863 , b = 8.350 , c = 9.043 , = 94.00°, = 97.81°, = 104.62°, Z = 1) was solved by direct methods and refined by full-matrix least-squares analysis in an anisotropic approximation to R = 0.048 for all 4570 reflections collected (CAD-4 automatic diffractometer, CuK ). The geometrical parameters of the organic cation were determined with a sufficient degree of accuracy. The crystal structure of I involves a very strong interionic hydrogen bond N⁺-HBr^–.Original Russian Text Copyright © 2004 by A. N. ChekhlovTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 759–763, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis and Structures of the Novel Pyridoxal Oxime Derivatives

Novel pyridoxal oxime derivatives were prepared and characterized by means of IR, ¹H and ¹³C NMR spectroscopy. The crystal structures of the 3-hydroxy-4-hydroxyiminomethyl-5-hydroxymethyl-1,2-dimethylpyridinium iodide 1 and 3-hydroxy-4-hydroxyiminomethyl-5-hydroxymethyl-1,2-dimethylpyridinium chloride monohydrate 2 were determined by X-ray analysis. The both compounds crystallize in the triclinic crystal system, space group P . Crystal data: 1 a = 6.286(2) Å, b = 8.748(4) Å, c = 11.736(4) Å, = 104.02(3)°, = 94.70(3)°, = 107.44(6)°, V = 589.0(4) ų, Z = 2, R = 0.0526; 2 a = 6.8980(5) Å, b = 8.6409(6) Å, c = 11.1777(6) Å, = 111.138(5)°, = 93.114(6)°, = 105.158(5)°, V = 591.57(7) ų, Z = 2, R = 0.0492. The bond distances and angles in both structures agree very well. The main difference between these structures was observed in the orientation of the hydroxymethyl group with respect to the pyridinium ring. In the both structures intramolecular hydrogen bond forming six-membered ring were observed. The intermolecular OsI hydrogen bonds in the crystal structure of the compound 1 form dimers. In the crystal structure of compound 2, the water molecules and chlorines build eight-membered rings, which are also connected to pyridinium cations by OsCl and OsO intermolecular hydrogen bonds forming a three-dimensional network.     

Mechanisms of Reactions of H2O and NH3 Molecules with (≡Si–O)3Si⋅and (≡ Si–O)3Si–⋅ Radicals on the Silica Surface

Spin traps, which are diamagnetic centers (SiO)₂Si, are used to register low-molecular radicals OH, NH₂, and H formed by the reactions of H₂O and NH₃ molecules with the radicals (Si–O)₃Si and (Si–O)₃Si–O stabilized on the silica surface. The experimental data and the results of quantum-chemical calculations for model systems are used to determine the mechanism and thermochemical characteristics of these reactions. A new paramagnetic center (Si–O)₂SiNH₂ was identified on the silica surface, and its radiospectroscopic characteristics are determined.     

Inclusion Compounds of NaI with 13-Membered Azo- and Azoxycrown Ethers

Sodium iodide complexes of 13-membered azo-(I)and azoxycrown ethers (II) have been synthesized. Compound I[Na(L1 trans)2]IH2O is triclinic witha = 11.53(2), b = 15.74(2), c = 19.17(2) Å, = 98.93(9), = 105.51(9), = 89.20(9) deg.; Z = 4, space groupP1. Compound II [Na(L2)2]I is orthorhombic witha = 12.451(2), b = 13.796(3), c = 18.667(4)Å; Z = 4, space group P2₁2₁2₁. In bothcomplexes the cation is coordinated tochain oxygen atoms and to one nitrogen atom of the azoor azoxy unit. The ability of bothligands to form complexes in relation to thegeometry of the azo or azoxy subunit of themacrocycle is discussed.     

Laser-spectroscopic laboratory studies of atmospheric aqueous phase free radical chemistry

Nitrate radical (NO₃) reactions with benzene (R-1), toluene (R-2), p-xylene (R-3), p-cresol (R-4) and mesitylene (R-5) have been studied by laser photolysis/long path laser absorption (LP-LPLA) in aqueous solution. Rate constants of k₁=(4.0±0.6) 10⁸, k₂=(1.2±0.3)10⁹, k₃=(1.6±0.1)10⁹, k₄= (8.4±2.3)10⁸ and k₅=(1.3±0.3)10⁹ lmol^-1s^-1 were obtained at T=298 K. In addition, reaction rate coefficients for SO^-₅+Fe²⁺prod. (R-6) and SO^-₅+Mn²⁺prod. (R-7) of k₆=(4.3±2.4) 10⁷ lmol^-1s^-1 and k₇=(4.6±1.0)10⁶ lmol^-1s^-1 (T=298 K, I0) have been obtained by the application of laser photolysis/UV-VIS broadband diode array spectroscopy. A new laser photolysis/UV-long path laser absorption experiment has been applied to study the reaction of the Cl^-₂ radical anion with dissolved sulfur(IV). For the reactions Cl^-₂+HSO^-₃2Cl^-+H⁺+SO^-₃ (R-8) and Cl^-₂+SO^2-₃2Cl^-+SO^-₃ (R-9) rate coefficients of k₈=(1.7±0.2)10⁸ lmol^-1s^-1 (T=298 K, I0) and of k₉=(6.2±0.3)10⁷ lmol^-1s^-1 (T=279 K, I0) were obtained.     

51V NMR studies of systems V2O5-KHSO4 and V2O5?K2SO4

Systems V₂O₅–KHSO₄ and V₂O₅–K₂SO₄ have been studied by the⁵¹V NMR method. The first system demonstrates the same states of vanadium as the previously studied V₂O₅–K₂S₂O₇, in this system a compound with an equimolar ratio of components has been found. In V₂O₅–K₂SO₄ the state of vanadium differs from the above systems and the formation of a compound with V/K=4 is observed.

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⁵¹V KHSO₄–V₂O₅ K₂SO₄–V₂O₅. , K₂S₂O₇–V₂O₅, . K₂SO₄–V₂O₅ V/K4.

     

Use of 2,4-dinitrophenylhydrazone of glyoxylic acid for the determination of glyoxylic acid by the chromatographic-spectrophotometric method and by differential pulse polarography

Two different methods (one based on chromatography and spectrophotometry and the other on polarography) have been developed for the determination of glyoxylic acid in the form of a derivative with 2,4-dinitrophenylhydrazine (DNPHGA). The TLC method allows the separation of two DNPHGA isomers (trans and cis). Spectrophotometric measurements of the eluents of the separated compounds (=360 nm) allow the determination of GA within the range from 4 to 30 g. Using differential pulse polarography, the conditions of DNPHGA formation were examined. The reduction peak of this derivative (E_P=–0.430 V), observed by dpp, was used to develop a polarographic determination of GA within the concentration range from 110^-4 to 710^–4 mol/l.     

Mercury(II) Compounds with 1,3-Benzothiazole-2-thione. Spectral, Thermal, and Crystal Structure Studies

Mercury(II) halides, HgX₂ (X = Cl^–, Br^–, I^–) react with 1,3-benzothiazole-2-thione (btztH) in methanol solutions giving the HgX₂(btztH) and HgX₂(btztH)₂ types of compounds. Mercury(II) acetate gives the thiolato compound Hg(btzt)₂ because of the deprotonation of btztH. Hg(btzt)₂ reacts with 2,2-bipyridine (bipy) giving a 1:1 complex. IR, ¹H, and ¹³C NMR spectral studies indicate that btztH acts as a monodenatate ligand through the S thione donor atom in all complexes. The X-ray crystal structure determinations of [HgI₂(btztH)]₂, HgBr₂(btztH)₂, Hg(btzt)₂, and Hg(btzt)₂(bipy) have been carried out revealing tetrahedrally coordinated mercury atom in [HgI₂(btztH)]₂ and HgBr₂(btztH)₂, while in Hg(btzt)₂(bipy) 2 + 2 coordination is achieved through strong Hg (N(bipy) contacts. A linear coordination in Hg(btzt)₂ is not affected by the Hg N contacts, which are longer than in Hg(btzt)₂(bipy), but still shorter than the van der Waals sum of mercury and nitrogen covalent radii. [HgI₂(btztH)]₂ exists as centrosymmetrical dimer with a Hg₂I₂ bridging core. The dimeric molecules are linked by the intermolecular hydrogen bonds between the terminal iodine atom and the NH group [3.63(1) Å] into infinite chains along the z-axis. There are N–H Br(bridging) intermolecular hydrogen bonds in HgBr₂(btztH)₂ joining molecules into endless chains along the x-axis. The Br(bridging) atom acts as double proton acceptor and two NH groups as proton donors [NH Br(bridging) 3.278(9) and 3.338(7) Å]. The mercury to sulfur and mercury to halogen bond distances in [HgI₂(btztH)]₂ and HgBr₂(btztH)₂ are discussed in relation to the analogous compounds, revealing strong influence of hydrogen bonds on their relative strengths as well as crystal packing requirements of the ligand. The sulfur and halogen atoms are more tightly bound to mercury implicating severe distortion of the coordination polyhedron in the structures in which they do not take part in hydrogen bonds formation. The influence of steric requirements of the ligands in Hg(btzt)₂ and Hg(btzt)₂(bipy) on the distortion of the mercury coordination polyhedra accompanied with the relative strength of Hg N contacts is considered.