Synthesis and thermal decomposition of Cr–urea complex

In this work, Cr–urea complex ([Cr(NH₂CONH₂)₆](NO₃)₃) was synthesized by direct solid-state reaction of chromium nitrate and urea, and its thermal decomposition reaction was studied for the first time to explore the possibilities of using the complex as precursor to nanosized chromium oxide. The formation of [Cr(NH₂CONH₂)₆](NO₃)₃ is confirmed from infrared spectroscopy and elemental analysis. Thermogravimetric and differential thermal analysis of the compound show a three-stage thermal decomposition in the temperature range from 190 to 430 °C. The result of X-ray diffraction (XRD) shows that the [Cr(NH₂CONH₂)₆](NO₃)₃ decompose at ~300 °C into α-Cr₂O₃ nanopowder with an average crystallite size of 33 nm.     

Synthesis,crystal structures,luminescence and thermal properties of lanthanide complexes containing 2,5-dichlorobenzoic acid and 2,2:6′,2″-terpyridine

Journal of Thermal Analysis and Calorimetry - Three novel ternary lanthanide complexes [Ln(2,5-DClBA)3(terpy)(H2O)] (Ln = Eu (1), Tb (2), Ho (3),...     

Kinetics of thermal decomposition of γ-irradiated and unirradiated complexes of mandelhydroxamic acid

The thermal decomposition of -irradiated and unirradiated complexes of mandel-hydroxamic acid (HMA), Co(HMA)₂.1/2H₂O, Mn(HMA)₂.2H₂O, Ba(HMA)₂.2H₂O and Cd(HMA)₂.2H₂O have been studied thermogravimetrically (under isothermal conditions). The thermal dehydration of each complex occurred in one step, while the decomposition of dehydrated complexes occurred in two steps. The kinetic parameters for dehydration were computed by different models. The thermal dehydration is regulated by random nucleation A₃ for Co-, Mn-, and Cd-complexes and by phase-boundary (R₃) for Ba-complex. The effect of -irradiation on the kinetic parameters of thermal decomposition is discussed. Radiation did not modify the mechanism of the reaction but accelarated the dehydration steps in the case of Mn- and Co-complexes.     

The thermal decomposition of metal complexes—IV: The preparation and thermal decomposition of some pyridine and substituted-pyridine complexes of nickel (II) halides

Complexes have been prepared between pyridine, α-, β- and γ-picoline, 2,6-lutidine, and s-collidine and nickel (II) chloride, bromide, and iodide. The thermal decomposition of these complexes has been studied. Diffuse reflectance spectra have been measured for all complexes and have been used to determine the environment about the nickel atoms.     

Production and thermal decomposition of polycondensates containing N,N′-disubstituted thiourea derivatives

Polycondensates containing N,N-ethylenethiourea or N,N-diisopropylthiourea units and titanium or silicon-derived coupling agent molecules were prepared. Their structures were confirmed through FTIR spectroscopy. The thermal decomposition of these polycondensates was studied by means of TG and DTA methods and FTIR and ESR spectroscopy.

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Zusammenfassung Es wurden Polykondensate mit einem Gehalt an N,N-Ethylenthiokarbamidoder N,N-Diisopropylthiokarbamideinheiten und mit Titan oder Silizium abgeleiteten Koppelreagenzmolekülen hergestellt. Ihre Struktur wurde mittels FTIR Spektroskopie bestätigt. Die thermische Zersetzung dieser Polykondensate wurde mittels TG und DTA Verfahren sowie mit Hilfe von FTIR und ESR Spektroskopie untersucht.

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The author thanks Professor P. I. Premovic for valuable discussions. This reseach was supported by the Research Fund of Macedonia, contract 10/1.     

Features of thermal decomposition of acrylates and methacrylates based on tert-butylperoxy-α-chloroalkoxyethanes

The kinetics of thermal decomposition of acrylic and methacrylic peroxides of general formula (CH₃)₃COOCH₂CH₂OCH(R¹)OC(O(R², where R¹ = H, Me, Et and R² = CH=CH₂, (CH₃)c=CH₂, Et, in the absence of solvent was studied.     

Reactions and thermal decomposition of organolithium compounds derived from 4,4′-dibromooctafluorobiphenyl

The lithiation of 4,4′-dibromooctafluorobiphenyl with n-butyllithium to yield 4,4′-dilithiooctafluorobiphenyl and 4-lithio-4′-bromooctafluorobiphenyl as a by-product under various conditions is described. It is proposed that thermal decomposition of the lithiated products formed at low temperatures (−80° to −90°) leads to products originating principally by nucleophilic displacement reactions, while rapid thermal decomposition, after metal-halogen interconversion at temperatures of 0°, leads principally to products originating by elimination reactions. The intermediacy of benzyne species is proposed on the basis of observed addition reactions with furan to give the adduct 1,1′,3,3′,4,4′-hexafluoro-5,8,5′,8′-tetrahydro-2,2′-binaphthyl 5,8,5′,8′-diepoxide.     

The thermal decomposition of freeze-dried tantalum and mixed lithium—niobium oxalate

A digital modification of a Perkin-Elmer thermobalance is described. This apparatus was used in conjunction with other thermal analysis equipment to study the thermal decomposition of NH₄Ta(C₂O₄)₃ · 2H₂O prepared by freeze-drying a commercial solution of the material. The major decomposition is in the region of 100–300 °C and the reaction is too complex to evaluate any intermediate steps. The amorphous oxide product crystallizes around 750 °C. This oxide is intimately mixed with carbon formed during the decomposition. The carbon burns off around 700–800 °C. However, if the decomposition is performed in hydrogen, the carbon remains and at about 1200 °C tantalum carbide is formed.A freeze-dried mixture of lithium and niobium oxalate was investigated to determine its suitability as a starting material for the preparation of lithium niobate. The decomposition of this material is compared to that of the conventional mixture of lithium carbonate and niobium oxide. The initial decomposition of the freeze-dried material around 100–400 °C leads to a mixture of lithium carbonate and niobium oxide but this subsequently reacts at about 500 °C to form lithium niobate. The conventional mixture of these materials does not react until around 750 °C. Surface area and electron micrographs indicate that lithium niobate having a particle size of 0.05 nm or larger can be prepared from the freeze-dried material.     

μ-Polymethylene bridged dicobaloximes: Structural, photolysis and thermal decomposition properties

A series of μ-polymethylene bridged dicobaloxime complexes py(dmgH)₂Co(CH₂)_nCo(dmgH)₂, where n = 4, 5, 6, and 12 (1-4) were synthesized and characterized. Crystal structures of py(dmgH)₂Co(CH₂)₄Co(dmgH)₂py · 2CH₂Cl₂ (1 · 2CH₂Cl₂), py(dmgH)₂Co(CH₂)₅Co(dmgH)₂py (2), and py(dmgH)₂Co(CH₂)₆Co(dmgH)₂py · CH₂Cl₂ (3 · CH₂Cl₂) have been determined by X-ray diffraction. Their structural features are compared with those reported for monocobaloxime complexes and oligomethylene-bridged vitamin B₁₂ dimer. 2-D layers or 3-D nets formed through intermolecular C-H?O interactions are observed in the molecular packing structures of 1 · 2CH₂Cl₂, 2, and 3 · CH₂Cl₂. The photolytic kinetic rates of the dicobaloximes were determined by UV-Vis spectroscopy and the products of photolytic solutions were characterized by ESI-MS. The results indicated that lengths of polymethylene have a little effect on the observed rate of the Co-C bond cleavage in our dicobaloxime complexes, while changing the solvent from methanol to ethanol has shown significant rate enhancement. In addition, TGA experiments for solid dicobaloxime complexes were performed to exam their thermal decomposition behaviors.     

Synthesis of 4-Bromo-1,1′:4′,1″-terphenyl and 4-Methyl-1,1′:4′,1″-terphenyl

Russian Journal of Organic Chemistry - Possible synthetic routes to 4-bromo-1,1′:4′,1″-terphenyl and 4-methyl-1,1′:4′,1″-terphenyl have been studied. Stevens...     

4′, 4″-Dihydroxy-3′,5′,3″,5″-tetrabrom-1,4-diphenyl-naphthalin-2, 3-dicarbonsäure-anhydrid

Ohne Zusammenfassung     

Concentration determination of I2 and I− formed by thermal and radiolytic decomposition of NaIO3

Journal of Radioanalytical and Nuclear Chemistry - As a part of the evaluation of radioactive iodine behavior under the severe accident condition of nuclear power plant, we measured the...     

New Synthesis of 3,3′,3″-Nitrilotripropionic Acid

Russian Journal of Organic Chemistry - A new procedure has been developed for the synthesis of 3,3′,3″-nitrilotripropionic acid (NTP) by reaction of formamide with acrylic acid in a...     

Crystal structure and thermal decomposition mechanism of the supramolecular complex of barium chloride with inositol

The single crystal of [Ba(H2O)2(C6H12O6)2Cl2] was obtained based on the phase equilibrium results. Its structure was determined by X-ray crystallographic analysis. The crystals are monoclinic and in space group C2/c with a=1.901 7(2) nm, b = 0.682 13(8) nm, c = 0.162 60(2) nm,β=96.593(2)°and V= 2.095 3(4) nm3, Z= 4, DC=1.917 g·cm-3. In its solid state, this supramolecular complex is a three-dimensional network with double layers connected by hydrogen bondings. The molecule structure of [Ba(H2O)2(C6H12O6)2Cl2] has a central barium ion that is coordinated to two water molecules, two chlorides, and four hydroxyls from the two inosi-tols. Losing the coordinating water is controlled by random nucleation and growth mechanism (n = 2/3) and 3-dimensional diffusion mechanism (n=2).     

DSC-TG studies on kinetics of curing and thermal decomposition of epoxy–ether amine systems

The cure behavior of diglycidyl ether of bisphenol A with a simple ether amine (4,7,10, trioxa -1,13, tridecane diamine), system I and a polyether amine (polypropylene glycol block polyethylene glycol block polypropylene glycol bis 2 amino propyl ether), system II was compared by Differential Scanning Calorimetry. The exothermicity of the curing reaction of system I is higher than that of system II (316 ± 15 J g^?1 for System I and 230 ± 15 J g^?1 for system II). Kinetic parameters viz., activation energy, pre-exponential factor, and rate constant for curing were evaluated by Kissinger method and Kissinger–Akahira–Sunose isoconversion method. Both systems showed low glass transition temperatures and System II shows a much lower T _g (?38 °C) than system I (26 °C). The thermogravimetric analysis of the two cured epoxy amine systems showed comparable thermal stability.     

Oligomeric allyl-palladium(II) complexes of β-substituted ethylselenolates: syntheses, structures and thermal decomposition

Tri-nuclear allyl-palladium complexes, [Pd(μ-SeCH(2)CH(2)COOR)(η(3)-C(3)H(4)R')](3) (R = H, Me, Et and R' = H, Me), have been synthesized by the reaction of [Pd(2)(μ-Cl)(2)(η(3)-C(3)H(4)R')(2)] with NaSeCH(2)CH(2)COOR. These complexes exist in a dynamic equilibrium with a dimeric form in solution and are fluxional at room temperature as shown by variable temperature (1)H NMR spectroscopy. The DFT calculations indicate that there is a negligible energy difference between the dimer and the trimer, and suggest that the delicate balance between the steric factors and angular strain decides the reaction products. These complexes (with R' = H) on treatment with [Pd(2)(μ-Cl)(2)(η(3)-C(3)H(5))(2)] afforded hetero-bridged complexes [Pd(2)(μ-Cl)(μ-SeCH(2)CH(2)COOR)(η(3)-C(3)H(5))(2)] (R = Me, Et). All the complexes have been characterized by NMR ((1)H, (13)C, (77)Se) spectroscopy. The molecular structure of [Pd(μ-SeCH(2)CH(2)COOEt)(η(3)-C(3)H(5))](3) revealed a chair conformation of the six-membered Pd(3)Se(3) ring, in which all the allyl groups lie at one side of the ring (similar to three axial 1,3,5-hydrogens of cyclohexane). Thermolysis of [Pd(μ-SeCH(2)CH(2)COOEt)(η(3)-C(3)H(5))](n) in diphenyl ether or hexadecylamine (HDA) yielded Pd(7)Se(4) as characterized by powder XRD.