A new oxidation process. Transformation of gem-bishydroperoxides into esters

A new oxidation process has been found where α,ω-dicarboxylic acid esters and ω-hydroxycarboxylic acid esters are formed on heating gem-bishydroperoxides in alcohol in the presence of BF₃·Et₂O. By addition of H₂O₂ to this reaction α,ω-dicarboxylic acid esters are formed almost selectively.     

Synthesis and crystal structures of two isomeric nitro-α-resorcylic acids

Nitration of α-resorcylic acid (3,5-dihydroxybenzoic acid) to 3,5-dihydroxy-2-nitrobenzoic acid (1) and 3,5-dihydroxy-4-nitrobenzoic acid (2), their separation, and crystallization is described. Crystal structures of 1, 1 · 3H₂O, and 2 were determined by X-ray single-crystal diffraction analysis and compared with DFT-calculated structures. An intramolecular hydrogen bond between the nitro group and o-hydroxyl group(s) occurs in all investigated structures. Intermolecular hydrogen bonds and π···π stacking interactions determine the molecular packing. Additionally, N···O interactions have a crucial role in arrangement of the molecules in the crystal structures of 1 and 2. DFT calculations in the gas phase and in the solution reveal that minor product 2 is a more stable regioisomer than 1, the major product in the nitration reaction.     

A study of the system CdO-SeO2-H2O at 25 and 100°C

The solubility of the system CdO-SeO₂-H₂O was studied at 25 and 100°C. The fields of crystallization of α-CdSeO₃, 3CdSeO₃·H₂SeO₃ and CdSeO₃·SeO₂ were established at 25°C. At 100°C crystallize α-CdSeO₃, 3CdSeO₃·SeO₂, 2CdSeO₃·SeO₂ and CdSeO₃·SeO₂. The compounds obtained were identified by means of chemical, X-ray and crystal-optical analysis. The mechanism of thermal dissociation of α-CdSeO₃, 3CdSeO₃·H₂SeO₃ and CdSeO₃·SeO₂ was studied. This revised version was published online in August 2006 with corrections to the Cover Date.     

Study of the crystallization fields of nickel(II) selenites in the system NiSeO3–SeO2–H2O

The solubility of NiSeO₃–SeO₂–H₂O system in the temperature region 298–573 K was studied. The compounds of the three-component system were identified by the Schreinemakers’ method. The phase diagram of nickel(II) selenites was drawn and the crystallization fields for the different phases were determined. Depending on the conditions for hydrothermal synthesis, NiSeO₃·2H₂O, α-NiSeO₃·1/3H₂O, β-NiSeO₃·1/3H₂O, NiSeO₃ and NiSe₂O₅ were obtained. The different phases were proved and characterized by chemical, powder X-ray diffraction and thermal analyses as well as IR spectroscopy.     

Effect of crystallization water and nature of an aluminum alkyl on the reduction of Eu3+ to Eu2+ in interaction of EuCl3 · 6H2O with Bu 3i Al and Et3Al

Volumetric and photoluminescence analytical techniques were employed to study the effect of crystallization water and nature of an aluminum alkyl on the reduction of Eu³⁺ to Eu²⁺ in a heterophase interaction of EuCl₃ · 6H₂O in toluene with Bu₃ⁱ Al and Et₃Al.     

“Direct” synthesis of unsolvated aluminum hydride involving Lewis and Bronsted acids

Unsolvated aluminum hydride has been synthesized by the “direct” reaction of aluminum bromide or sulfuric acid with an alkali metal tetrahydroaluminate at 90–102°C in pure toluene or in toluene containing 5–10 wt % diethyl ether. The reaction involving aluminum bromide yields a mixture of unsolvated aluminum hydride phases of poor quality. The reaction with sulfuric acid affords a single-phase product as α-AlH₃ at ≤90°C.     

Synthesis, crystal structure and characterization of a 2-D network organic-inorganic hybrid polymer with [α-BW12O40]5? as building blocks

A two-dimensional network compound [Ce(DMF)₄(H₂O)][α-BW₁₂O₄₀]·H₂O·(HDMA)₂ (HDMA = protoned dimethylamine, DMF = N,N-dimethylformamide) was synthesized from α-H₅BW₁₂O₄₀·nH₂O, Ce(NO₃)₃·6H₂O and DMF and characterized by IR, UV spectra and TG-DTA. The result of the X-ray single crystal diffraction indicates that the crystal is monoclinic, space group P2₁/n, with unit cell dimensional: a = 1.1983(3), b = 2.4216(5), c = 1.9517(4) nm, β = 92.91(3)°, Z = 4, R ₁ = 0.07710, wR ₂ = 0.1416. Structural analysis indicates that every [Ce(DMF)₄(H₂O)]³⁺ building block is surrounded by three adjacent [α-BW₁₂O₄₀]⁵⁻ polyanions, meanwhile, every [α-BW₁₂O₄₀]⁵⁻ polyanion interconnects with three neighboring [Ce(DMF)₄(H₂O)]³⁺ subunits, by making use of which two-dimensional network structure can be constructed. The result of thermogravimetric analysis manifests that the title compound has two-stage weight loss and the decomposition temperature of the title polyanionic framework is 560°C. The electrochemical analysis shows the title polyanion has three-step redox processes in the pH = 4–7 media.     

Bis(citrato)hydroxogermanic(IV) acid dimer [H5O2][Ge(H2Cit)(H2.5Cit)(OH)]2 · 2CH3COOH · 2H2O: Synthesis, properties, and crystal and molecular structure

Bis(citrato)hydroxogermanic(IV) acid was obtained for the first time in the complex [H₅O₂][Ge(H₂Cit)(H_2.5Cit)(OH)]₂ · 2CH₃COOH · 2H₂O (H₄Cit is citric acid). The complex was characterized by chemical analysis, X-ray powder diffraction, TGA, and IR spectroscopy. Complex I was studied by X-ray crystallography. The crystals are triclinic; a = 10.0651(4) ?, b = 10.1918(4) ?, c = 10.5838(4) ?, α = 85.0110(10)°, β = 85.2170(10)°, γ = 86.7670(10)°, V = 1076.50(7) ?³, Z = 1, space group P[`1]P\bar 1, R1 = 0.0353 for 5709 reflections with I > 2σ(I). Complex I is composed of centrosymmetric dimeric complex anions [Ge₂(H₂Cit)₂(H_2.5Cit)₂(OH)₂]⁻, dioxonium cations [H₅O₂]⁺, and acetic acid and water molecules of crystallization. The coordination polyhedron of the Ge atom is a trigonal bipyramid. Its equatorial plane comprises two O atoms of the deprotonated alcohol groups of two ligands H₂Cit (A) and H_2.5Cit (B) and the O atom of the terminal OH group (Ge-O, 1.7585–1.7754 ?; O_eqGe(1)O_eq, 116.26°–127.64°). The axial positions are occupied by the carboxy O atom of the deprotonated carboxylate group of the α branch of ligand A (α-Ge-O(C)(carb), 1.8882(12) ?)) and the carbonyl O atom of the hemiprotonated acetate α branch of ligand B (α-Ge-O(C) 1.9615(12) ?, O(1)Ge(1)O(8) 170.47(5)°). In structure I, the complex dianion, the cation, and acetic acid and water molecules are united through hydrogen bonds into a three-dimensional framework.     

Picoline as ligand with antimony trichloride and triiodide adducts

Solid adducts SbX₃·L-pic (X=Cl, I and L=α-, β- and γ-picolines) were synthesized and characterized by elemental analysis, ¹H and ¹³C NMR, IR spectroscopy and thermal analysis. The infrared spectroscopy and the magnetic resonance for ¹H and ¹³C nuclei of these compounds suggest that the ligands coordinate through nitrogen atom. Kinetic studies were accomplished by means of thermogravimetric data, through isothermal and non-isothermal techniques. The best adjusting models for adducts thermal decomposition were R¹ for isothermal and R₁ and R₂ for the non-isothermal methods. The energy of activation values obtained by isothermal method indicate the following orders of thermal stability for adducts: i) SbCl₃·α-pic>SbCl₃·β-pic>SbCl₃·γ-pic and ii) SbI₃·β-pic>SbI₃·γ-pic>SbI₃·α-pic. The activation energy values obtained by non-isothermal were higher than those from isothermal methods, showing the order of stability:iii) SbCl₃·α-pic<SbCl₃·β-pic<SbCl₃·γ-pic and iv) SbI₃·β-pic>SbI₃·α-pic=SbI_3··γ-pic. These obtained data through R₁ model presented the kinetic compensation effect for trichloride adducts, which could be associated to both isothermal and non-isothermal processes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cationic polymerizations of substituted 2-methylene-1,3-dioxocyclic acetals, 2-methylene-1,3-dithiolane and copolymerization of 2-methylene-1,3-dithiolane with 4-(t-butyl)-2-methylene-1,3-dioxolane1

Carbon black-supported sulfuric acid or BF₃·Et₂O-initiated polymerizations of 2-methylene-4,4,5,5-tetramethyl-1,3-dioxolane (1), 2-methylene-4-phenyl-1,3-dioxolane (2), and 2-methylene-4-isopropyl-5,5-dimethyl-1,3-dioxane (3) were performed. 1,2-Vinyl addition homopolymers of 1–3 were produced using carbon black-supported H₂SO₄ initiation at temperatures from 0°C to 60°C whereas both ring-opened and 1,2-vinyl structural units were present in the polymers using BF₃·Et₂O as an initiator. Cationic polymerizations of 2-methylene-1,3-dithiolane (4) and copolymerization of 4 with 2-methylene-4-(t-butyl)-1,3-dioxolane (5) were initiated with either carbon black-sulfuric acid or BF₃·Et₂O. Insoluble 1,2-vinyl addition homopolymers of 4 were obtained upon initiation with the supported acid or BF₃·Et₂O. A soluble copolymer of 2-methylene-1,3-dithiolane (4) and 4-(t-butyl)-2-methylene-1,3-dioxolane (5) was obtained upon BF₃·Et₂O initiation. This copolymer is composed of three structural units: a ring-opened dithioester unit, a 1,2-vinyl-polymerized 1,3-dithiolane unit, and a 1,2-vinyl polymerized 4-(t-butyl)-1,3-dioxolane unit. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2823–2840, 1999     

Kinetics and thermodynamics of thermal decomposition of NH<Subscript>4</Subscript>NiPO<Subscript>4</Subscript>·6H<Subscript>2</Subscript>O

The single phase NH₄NiPO₄·6H₂O was synthesized by solid-state reaction at room temperature using NiSO₄·6H₂O and (NH₄)₃PO₄·3H₂O as raw materials. XRD analysis showed that NH₄NiPO₄·6H₂O was a compound with orthorhombic structure. The thermal process of NH₄NiPO₄·6H₂O experienced three steps, which involves the dehydration of the five crystal water molecules at first, and then deamination, dehydration of the one crystal water, intramolecular dehydration of the protonated phosphate groups together, at last crystallization of Ni₂P₂O₇. In the DTA curve, the two endothermic peaks and an exothermic peak, respectively, corresponding to the first two steps’ mass loss of NH₄NiPO₄·6H₂O and crystallization of Ni₂P₂O₇. Based on Flynn–Wall–Ozawa equation, and Kissinger equation, the average values of the activation energies associated with the thermal decomposition of NH₄NiPO₄·6H₂O, and crystallization of Ni₂P₂O₇ were determined to be 47.81, 90.18, and 640.09 kJ mol⁻¹, respectively. Dehydration of the five crystal water molecules of NH₄NiPO₄·6H₂O, and deamination, dehydration of the crystal water of NH₄NiPO₄·H₂O, intramolecular dehydration of the protonated phosphate group from NiHPO₄ together could be multi-step reaction mechanisms. Besides, the thermodynamic parameters (ΔH ^≠, ΔG ^≠, and ΔS ^≠) of the decomposition reaction of NH₄NiPO₄·6H₂O were determined.     

Synthesis and characterization of two inorganic–organic hybrid polyoxometalates bridged by Keggin-type building blocks and copper(II) organonitrogen complexes

Two new inorganic–organic hybrid compounds, namely [Cu(dab)₂]₂[α-SiW₁₂O₄₀]·H₂O (dab = 1,2-diaminobenzene) and [Cu(dafo)₃]₂[Cu(dafo)₂(H₂O)₂][α-PMo₁₂O₄₀]₂·4H₂O (dafo = 4,5-diaza- fluorene-9-one) have been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. [Cu(dab)₂]₂[α-SiW₁₂O₄₀]·H₂O exhibits an alternating 2D ladder-like structure built of [α-SiW₁₂O₄₀]⁴⁻ and [Cu(L)₂]²⁺ units. As the inorganic building block, the Keggin-type polyoxoanion [α-SiW₁₂O₄₀]⁴⁻ is linked to two metal–organic complexes [Cu(dab)₂]²⁺ through different kinds of oxygen atoms (terminal and bridging). [Cu(dafo)₃]₂[Cu(dafo)₂(H₂O)₂][α-PMo₁₂O₄₀]₂·4H₂O shows an extended 3D supramolecular network via hydrogen bonding. Both complexes were characterized by physico-chemical and spectroscopic methods.     

Physicochemical modeling of precipitating and dissolving of gypsum in chloride solutions

Physicochemical modeling is used to study the isolation of sulfate ions as α (β)-CaSO₄ · 2H₂O from aqueous solutions. The equilibrium compositions of liquid, solid, and gas phases of the NA₂SO₄-CaCl₂-CO₂-H₂O system are calculated at 25°C, CO₂ partial pressures of 10^−1.53 kPa, CaCl₂/Na₂SO₄ molar ratios of 0.2–3.0, and CaCl₂ concentrations from 0.01 to 0.15 mol/kgH₂O. The Gibbs energies of formation for α(β)-gypsum were determined from experimental solubility data on the α(β)-gypsum-air-water system by solving the inverse problem of physicochemical modeling. The data obtained are ΔG° _f298 (α-CaSO₄ · 2H₂O) = −1796.446 kJ/mol and G° _f298 (β-CaSO₄ · 2H₂)) = −1797.317 kJ/mol. Published in Russian in Zhurnal Neorganicheskoi Khimii, 2006, Vol. 51, No. 5, pp. 889–894. This article was translated by the authors.     

Synthesis of trialkylaluminum derivatives by the reaction of non-solvated aluminum hydride with α-olefins

Hydroalumination of -olefins by non-solvated polymeric aluminum hydride (AlH₃) _n occurs at 120—140 °C. Mechanochemical activation accelerates this reaction. The addition of catalytic amounts of the prepared R₃Al forms to the reaction system decreases the temperature of the process to 90—100 °C. The greatest initiation effect is observed when ate-complexes of the MAlR₄ type (M = Li, Na) are used: the reaction occurs with a higher rate already at 60—90 °C affording R₃Al free of admixtures of carbalumination products and dimers of -olefins.     

Synthesis, structural characterization and properties of a 3D infinitely extended structural rare earth coordination compound of K3{[Sm(H2O)7]2Na[α-SiW11O39Sm(H2O)4]2} · 14 H2O· 14 H2O

A 3D infinitely extended structural rare earth coordination compound with a formula of K₃{[Sm(H₂O)₇]₂Na[α-SiW₁₁O₃₉Sm(H₂O)₄]₂}·14H₂O has been synthesized by reaction of Sm₂O₃, HClO₄, NaOH with α-K₈SiW₁₁O39·nH₂O, and characterized by IR, UV spectra, ICP, TG-DTA, cyclic voltammetry, variable-temperature magnetic susceptibility and X-ray single-crystal diffraction. X-ray single-crystal diffraction indicates that the title compound crystallizes in a triclinic lattice, Pī space group, with a = 1.2462(3) nm, b = 1.2652(3) nm, c = 1.8420(4) nm, α = 87.45(3)°, β = 79.91(3)°, γ= 82.57(3)°, Z = 1, R₁ = 0.0778, wR₂ = 0.1610. Structural analysis reveals that Sm³⁺(1) coordination cation has incorporated into the vacant site of [α-SiW11O₃₉]⁸⁻ entity, forming the [α- SiW₁₁O₃₉Sm(H₂O)₄]⁵⁻ subunit. The two adjacent [α-SiW₁₁O₃9Sm(H₂O)4]⁵⁻ subunits are combined with each other through two Sm(1)-O-W bridges accompanying the formation of dimmer structural unit [α-SiW₁₁O₃₉Sm(H₂O)₄]₂ ¹⁰⁻ of the title compound. The neighboring dimmer structural units [α-SiW₁₁O₃₉Sm(H₂O)₄]₂ ¹⁰⁻ are linked to form the 1D chainlike structure by means of two Sm³⁺(2) and a Na⁺(1) coordination cations. The K⁺(1) cations connect the 1D packing chains constructing the 2D netlike structure, and adjacent netlike layers are also grafted by K⁺(2) cations to build the novel 3D infinitely extended structure. The result of TG-DTA curves manifests that the decomposition temperature of the title polyanionic framework is 554°C. The cyclic voltammetry measurements show that the title polyanion has the two-step redox processes in aqueous solution with pH = 3.1. Variable temperature magnetic susceptibility indicates the title compound obeys the Cruie-Weiss Law in the higher temperature range from 110 to 300 K, while in the lower temperature range from 2 to 110 K the comparatively strong antiferromagnetism interactions can be observed.     

The ESR study of the structure and reactivity of α-ketoradicals, derivatives of (CF3)3CC(O)C(O)CF3

The structure and reactivity of α-ketoradicals, derivatives of (CF₃)₃CC(O)C(O)CF₃ (1), were studied by ESR spectroscopy. The photoreduction of α-diketone1 in a solution of cyclohexane in perfluorodipentyl ether results in the formation of radicals of two types, (CF₃)₃CC(2)(O(4))·C(3)(O(6)H)CF₃ (1a) and (CF₃)₃C·C(OH)C(O)CF₃ (1b) in a ∼40∶1 ratio. The degree of delocalization of the spin density in two conformers of radical1a was calculated by the MNDO/PM3 method in the UHF approximation. It was established that radicals1a and1b are capable of reversible dimerization. The rate constant of dimerization and the enthalpy of the radical—dimer equilibrium were measured for radical1a. A decrease in the rate of dimerization of radical1a upon addition of complexing solvents ((CF₃)₃COH andp-CF₃C₆H₄CF₃) was found. The influence of the solvents on the rate of dimerization was also detected for α-ketoradical (CF₃)₃CC(O)·C(OSiMe₂Ph)CF₃ (1c). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 62–67, January, 1998.     

Syntheses, Structures, and Nonlinear Optical Properties of Two Crown-like Heteroselenometallic Compounds [Et4N]4[(μ5-WSe4)(CuX)5(μ-X)2] (X = Cl, Br)

Two isostructural crown-like heteroselenometallic cluster compounds, [Et₄N]₄[(μ₅-WSe₄)(CuX)₅(μ-X)₂] (X = Cl 1, Br 2), were prepared from the reactions of [Et₄N]₂[WSe₄] with CuX and [Et₄N]X· xH₂O in the presence of 2-picoline and characterized by single-crystal diffraction analysis. The [(μ₅-WSe₄)(Cu-X)₅(μ-X)₂]⁴⁻ anions in the cluster compounds consists of five CuX fragments coordinated to the five edges of the tetrahedral [WSe₄]²⁻ moiety along with two bridging halides connected to each of the two pairs of the symmetric copper atoms, exhibiting a novel crown-like core structure. The nonlinear optical absorption and refraction of cluster compound 2 were determined to be α₂ = 6.15 × 10⁻¹⁰ m/W and n ₂ = 4.18 × 10⁻¹¹ esu, respectively.     

Synthesis of substituted 2-amino-1,3-thiazine-6-thiones

The reaction of thiourea with l-acyl-2-bromoacetylenes in AcOH in the presence of BF₃·Et₂O affords 2-amino-4-phenyl(2-thienyl)-1,3-thiazine-6-thiones in high yields. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 11, pp. 1947–1949, November, 2000.