Structure,thermal stability and decomposition of bis-allyl-zinc compounds

The structure, thermal stability and decomposition of solutions of diallylzinc (I), bis(2-methylallyl)zinc (II), bis(3-methylallyl)zinc (III) and bis(3,3-dimethylallyl)zinc (IV) in deuterated solvents, have been investigated by¹H NMR and by kinetic measurements at temperatures between ?125 and +180°C. At room temperature I, II, III and IV are dynamic systems and are best described as being rapidly equilibrating mixtures of all isomeric σ-allyl forms; the NMR spectra are averages weighted according to the relative concentrations of the respective forms. I displays a¹H NMR spectrum of a static σ-allyl system only below ?125°C and II only below ?115°C. At temperatures above 100°C the thermal decomposition of I–IV results in coupling of the allyl groups, decomposition via radicals being the major process. The coupled products exhibit CIDNP, in which the multiplet polarisations confirm a decomposition via randomly diffusing allyl radicals. In the allyl radicals CH₂CR¹CR²R³ an alternating spin density was proved experimentally. The thermal stability decreases in the order I > II > III > IV.     

Thermal decomposition of lead titanyl oxalate tetrahydrate

The thermal behaviour of PbTiO(C₂O₄)₂·4H₂O (PTO) has been investigated, employing TG, quantitative DTA, infrared spectroscopy and (high temperature) X-ray powder diffraction.The decomposition involves four main steps. The first is the dehydration of the tetrahydrate (30–180°C), followed by a small endothermic (270–310°C) and a large exothermic decomposition of the oxalate. The main (exothermic) oxalate decomposition (310–390°C) results in a stable oxide-carbonate PbTiO₂₅.(CO₃)_0.5. In the last step a phase transition, release of CO₂ and ordering of the crystalline cubic PbTiO₃ lattice can be detected (460–530_C).It can be argued that for thermodynamic reasons the presence of lead-oxo- carbonates in the oxide-carbonate intermediate is not possible.No differences could be found in thermal behaviour of two crystallographically different synthetic forms of PTO, of which one has an orthorhombic lattice.     

Thermal behaviour of two new salts of malonic acid: Cu(C3H2O4)·4H2O and Cu(NH4)2(C3H2O4)2

Two new salts of malonic acid have been prepared: the copper(II) malonate tetrahydrate and the copper(II)-ammonium double malonate. Their study by thermal analysis (TG and DTA) leads to the following results:Cu(C₃H₂O₄)·4H₂O: the dehydration is rather complex and it is only under careful conditions that an intermediate hydrate Cu(C₃H₂O₄)·3H₂O could be traced. At about 170°C the dehydration is not ended (the salt holds yet about 0.15H₂O) and the anhydrous salt occurs only at about 240°C. It decomposes immediately leading to residues the composition of which depends upon the surrounding atmosphere; the part played by the gas given off is discussed.Cu(NH₄)₂(C₃H₂O₄)₂: this salt melts and decomposes simultaneously at about 190°C. During the decomposition the copper nitride Cu₃N forms as intermediate compound (as well as copper metal). Concerning the final residues of the decomposition the results and the conclusions are the same as the ones of the previous case.     

Factors influencing the thermal decomposition of transition metal complexes with 2-OH-aryloximes under nitrogen

Summary The thermal behavior of copper(II), nickel(II) and palladium(II) complexes with two anionic varieties of 2-OH-aryloximes (ox), [M(ox)₂] (2-hydroxypropiophenonoxime and 2-hydroxy-4-methoxy-benzophenonoxime) was studied by using simultaneous TG/DTG-DTA technique under nitrogen in the temperature range 40-700°C. The behavior was compared with that in static air, which had been previously studied. It was found that the metal, the substituents on the ligand and the heating rate influenced their thermal decomposition. The thermal stability of the complexes with the same ligand depended on the metallic cation, following the order Pd(II)>Ni(II)>Cu(II). It also depended on the type of ligand, increasing with bulky substituents on the oximic carbon and the benzene ring. The sample mass almost did not affect their decomposition mode. The residues at 700°C of all complexes consisted of a carbonaceous oxide, determined by energy dispersive spectrometry (EDS) and IR spectroscopy     

Darstellung und Kristallstruktur von Ptl3, einem valenzgemischten Platin (II,IV)-iodid

Preparation and Crystal Structure of PtI₃, a Mixed-valence Platinum (II, IV) Iodide PtI₃ was obtained by thermal decomposition of PtI₄ in a closed system at 300°C and 8 atm iodine pressure. Single crystals were formed by the reaction of PtI₄ with aqueous solutions of KI and I₂ at 270°C. The crystal structure of the monoclinic compound (a = 673.5(2) pm; b = 1206.1(4) pm; c = 1331.3(5) pm; β = 101.25(6)°; Z = 8; space group C2/c-C_2h⁶) contains square planar PtI₄ and octahedral PtI₆ groups which are connected by common edges to chains.     

Synthesis and Thermal Study of Magnesium Complexes with 8-hydroxyquinolinate Derivatives

Magnesium ion was reacted with 5,7-dibromo-, 5,7-dichloro-, 7-iodo-and 5-chloro-7-iodo-8-hydroxyquinoline, in acetone/ammonium hydroxide medium under constant stirring to obtain (I) Mg[(C₉H₄ONBr₂)₂]·2H₂O; (II) Mg[(C₉H₄ONCl₂)₂]·3H₂O; (III) Mg[(C₉H₅ONI)₂]·2H₂O and (IV)Mg[(C₉H₄ONICl)₂]·2.5H₂O complexes. The compounds were characterized by elemental analysis, IR spectra, ICP, TG-DTA and DSC. Through thermal decomposition residues were obtained and characterized, by X-ray diffractometry, as a mixture of hexagonal MgBr₂ and cubic MgO to the (I) compound at 850°C; cubic MgO to the (II), (III) and (IV) compounds at750, 800 and 700°C, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of the thermal decomposition on Pt(II) complexes with cycloalkanespiro-5′-hydantoins

The thermal decomposition of the Pt(II) complexes with cyclobutane-and cycloheptanespiro-5′-hydantoins were studied by TG and DTA techniques. The Pt(II) complex with cyclobutanespiro-5′hydantoin (PtCBH) was stable up to 115°C (388 K) and Pt(II) complex with cycloheptanespiro-5′-hydantoin (PtCHTH) was stable up to 150°C (423 K). After the thermal decomposition of PtCBH the solid residue was platinum, while the decomposition of PtCHTH gave a mixture of platinum carbides (PtC₂, Pt₂C₃).     

Evaluation of cation influence on the formation of M(II)Cr2O4 during the thermal decomposition of mixed carboxylate type precursors

This paper reports an investigation regarding the influence of the cation M(II) (M = Zn, Ni, Mg) on the formation of MCr₂O₄ by thermal decomposition of the corresponding M(II),Cr(III)-carboxylates (precursors) obtained by redox reaction between the corresponding metal nitrates and 1,3-propanediol. The decomposition products at different temperatures have been characterized by FT-IR spectroscopy and thermal analysis. Thus, we have evidenced that by thermal decomposition of the studied precursors in the range 250–300 °C, different amorphous oxidic phases mixtures form depending on the nature of metalic cation: (Cr₂O_3+x + ZnO) (Cr₂O_3+x + Ni/NiO) and (Cr₂O_3+x+MgO). In case of M = Zn, around 400 °C when the transition Cr₂O_3+x to Cr₂O₃ takes place, zinc chromite nuclei form by the interaction ZnO with Cr₂O₃. In case of M = Ni, due to the partial reduction of Ni(II) at Ni(0) during the thermal decomposition of the precursor the formation of nickel chromite by the reaction NiO + Cr₂O₃ is shifted toward 500 °C, when Ni is oxidized at NiO. The thermal evolution of the mixture (MgO + CrO₃) is different due to the formation as intermediary phase of MgCrO₄, which decomposes to MgCr₂O₄ around 560 °C. In order to investigate the chromites formation mechanism, we have studied the mechanical mixtures of single oxides obtained from the corresponding carboxylates. These mixtures (MO + Cr₂O₃) have been annealed at 400, 500, and 600 °C to study the evolution of the crystalline phases. It results in the prepared mixture behaving different from the mixtures obtained by thermal decomposition of the binary M(II),Cr(III)-carboxylates, recommending our synthesis method for obtaining binary oxides.     

The thermal properties of cobalt(II), nickel(II) and copper(II) iminodiacetates

The thermal properties of the Cu(II), Ni(II) and Co(II) complexes of iminodiacetic acid (H₂IMDA) were determined using TG, DTG and DSC techniques. The complexes, of general formula, MIMDA-2H₂O evolved water of hydration from 50 to 150°C which was followed by the decomposition of the anhydrous complex in the 250 to 400°C temperature range. The thermal stability, as determined by procedural decomposition temperatures, was: Ni(II) >Co(II) >Cu(II). The thermal stability is discussed in terms of IR spectra, ΔH, and ΔS, as well as thermal data.     

Synthesis,characterization, and thermal study of solid-state alkaline earth metal mandelates,except beryllium and radium

Characterization, thermal stability, and thermal decomposition of alkaline earth metal mandelates, M(C₆H₅CH(OH)CO₂)₂, (M = Mg(II), Ca(II), Sr(II), and Ba(II)), were investigated employing simultaneous thermogravimetry and differential thermal analysis or differential scanning calorimetry, (TG–DTA or TG–DSC), infrared spectroscopy (FTIR), complexometry, and TG–DSC coupled to FTIR. All the compounds were obtained in the anhydrous state and the thermal decomposition occurs in three steps. The final residue up to 585 °C (Mg), 720 °C (Ca), and 945 °C (Sr) is the respective oxide MgO, CaO, and SrO. For the barium compound the final residue up to 580 °C is BaCO₃, which is stable until 950 °C and above this temperature the TG curve shows the beginning of the thermal decomposition of the barium carbonate. The results also provide information concerning the thermal behavior and identification of gaseous products evolved during the thermal decomposition of these compounds.     

Heterogeneous reactions of solid nickel(II) complexes XXIV

The Stoichiometry of thermal decomposition was studied for the following compounds: Ni(NCS)₂(pip)₄ (I), (pip=piperidine), Ni(NCS)₂(pip)₂py·H₂O (II), (py=piridine), Ni(NCS)₂(4-Mepip)₃ (III), Ni(NCS)₂(3-Mepip)₃ (IV) and Ni(NCS)₂(3.5-Me₂pip)₃ (V). In complexes I, II, III and IV the loss of the volatile ligands (on the TG curve to 300 °C) occurs in three steps and in complex V in two steps. The loss of the last molecules of volatile ligands is accompanied by the decomposition of NCS groups. Spectral data and magnetic moment values for the initial complexes I and II (together with the defined intermediates) indicated pseudooctahedral configuration while pentacoordination for complexes III, IV and V. Structural changes of the complexes studied in thermal decomposition reactions are discussed.     

Insect pheromones and their analogs

A four-stage asymmetric synthesis of (+)-disparlure [(7R,8S)-(+)-cis-methyl-7,8-epoxyoctadecane (V)] has been effected from 8-methylnon-2Z-en-l-ol (I), obtained by the carboalumination of acetylene with tris(5-methylhexyl)aluminum using the Sharpless reaction. The asymmetric epoxidation of (I), (Ar, mol. sieve A, (+)-DET, (iOPr)₄Ti, t-BuOOH, ?15°C, 20 h; H₂O, 1 h, NaOH, ?7°C, 30 min) gave 8-methyl-2S,3R-epoxynonan-l-ol (II), which was oxidized (kieselguhr-CrO₃-Py, 0°C, 2 h; 25°C, 2 h) to 8-methyl-2S,3R-epoxynonan-l-al (III). The coupling of (III) with n-C₈H₁₇CH=PPh₃ (?78°C, 1 h; 25°C, 15 h) gave 2-methyl-7R,8S-epoxyoctadec-9Z-ene (IV), the hydrogenation (H₂/5% Pd-C, 25°C, 5 days) of which led to (V) in admixture with an isomerization product. Compound (V) was isolated by HPLC. Substance, yield, [α] _D ²⁵ : (II), 73, ?2.75°; (III), 80, [80.8°; (IV), 50, +37.25°; (V), 50, +0.8°. The IR and PMR spectra of (II–IV), the¹³C NMR spectra of (II) and (III), and the mass spectrum of (IV) are given.     

The thermal properties of the copper(II), nickel(II) and cobalt(II) glycinates

The thermal properties of the Ni(II), Co(II) and Cu(II) complexes of glycine were determined using TG, DTG and DSC techniques. The complexes, MGly₂·nH₂O (n = 1, 2), dehydrated in the temperature range of 75 to 200°C, followed by the decomposition of the anhydrous compounds in the temperature range of 200 to 400°C. The thermal stability of the complexes, as determined by procedural decomposition temperatures, was: Ni(II) >Co(II) >Cu(II).     

Thermal decomposition of potassium chlorate in presence of chromium(III) oxide and nickel(II) chromite(III)

A study of thermal behaviour of intimate mixtures of different molar ratios of potassium chlorate and chromium(III) oxide, and potassium chlorate and nickel(II) chromite(III) was made by employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray powder diffraction analysis. Potassium chlorate in presence of Cr(III), starts decomposing around 200°C which is much below the decomposition temperature of pure KClO₃. Each mole of Cr(III) takes up 8/3 moles of KClO₃ to become oxidized into potassium dichromate.     

Novel Cobalt(II), Nickel(II) and Copper(II) Complexes of Neutral Orotic Acid. Synthesis,Spectroscopic and Thermal Studies

The new orotic acid complexes, [MCl₂(H₂O)₃(H₃Or)], M=Co(II), Ni(II) and [CuCl₂(H₂O)(H₃Or)₃] · H₂O, were synthesized and characterized by elemental analysis, magnetic susceptibility, spectral (Diffuse reflectance UV–Vis and FTIR) methods, and simultaneous thermal analysis (TG, DTG and DTA) techniques. Physical measurements indicate that the neutral orotic acid ligands are bonded to metal ions through the carbonyl groups. Two thermal processes of the complexes can occur: dehydration and pyrolytic decomposition. On the basis of the DTG_max, the thermal stability of the complexes follows the order: Co(II) (122 °C) > Cu(II) (77 °C) > Ni(II) (66 °C).     

Evolution of yttrium trifluoroacetate during thermal decomposition

A detailed analysis of the thermal decomposition of yttrium trifluoroacetate under different atmospheres is presented. Thermogravimetry, differential thermal analysis, and evolved gas analysis have been used for this in situ analysis. Solid residues at different stages have been characterized by means of X-ray diffraction, elemental analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The first decomposition stage (310 °C) is exothermic and involves the complete removal of carbon (organic part) and the formation of yttrium fluoride. This process is characterized by a fast mass loss rate. Afterwards, yttria (Y₂O₃) is formed at 1200 °C through a slow process controlled by the out diffusion of fluorine that involves the formation of yttrium oxyfluoride as an intermediate. The evolution of the mass during the decomposition and the structure of the yttria particles is not affected by the presence of oxygen or water. However, when the oxygen (water) partial pressure is as low as 0.02% (<0.002%), the kinetics and final particle structure are strongly affected.     

TG–MS–FTIR (evolved gas analysis) of kaolinite–urea intercalation complex

The products evolved during the thermal decomposition of kaolinite–urea intercalation complex were studied by using TG–FTIR–MS technique. The main gases and volatile products released during the thermal decomposition of kaolinite–urea intercalation complex are ammonia (NH₃), water (H₂O), cyanic acid (HNCO), carbon dioxide (CO₂), nitric acid (HNO₃), and biuret ((H₂NCO)₂NH). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved products CO₂, H₂O, NH₃, HNCO are mainly released at the temperature between 200 and 450 °C with a maximum at 355 °C; (2) up to 600 °C, the main evolved products are H₂O and CO₂ with a maximum at 575 °C. It is concluded that the thermal decomposition of the kaolinite–urea intercalation complex includes two stages: (a) thermal decomposition of urea in the intercalation complex takes place in four steps up to 450 °C; (b) the dehydroxylation of kaolinite and thermal decomposition of residual urea occurs between 500 and 600 °C with a maximum at 575 °C. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanation have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials and its intercalation complexes.     

Thermal decomposition of the biguanide complexes of the 3d-transition metals

The thermal decomposition (TG, DTG and DTA) of the complexes of biguanide with the following metals was studied: V, Cr, Mn, Co, Ni, Cu and Zn. Structural water, when present, is first eliminated at ～100–150°C; this is followed by a main decomposition state at ～300–350°C. Pyrolytic residues are analysed and characterised by their x-ray powder diffraction patterns and are found to be the oxides V₂O₅, Cr₂O₃, Mn₃O₄, Co₃O₄, NiO, CuO and ZnO, respectively. The decomposition curves of the free ligand (biguanide) and biguanide sulphate are also given. The decomposition characteristics are discussed.     

Thermal decomposition of cerium(III) perchlorate

Thermal decomposition of Ce(ClO₄)₃ ? 9H₂O and Ce(ClO₄)₃ to give cerium(IV) dioxide in the temperature range 240–460°C was studied by DSC–TGA, X-ray powder diffraction, IR and mass spectroscopy. The thermolysis of these salts was shown to proceed through the stage of formation of intermediate product supposedly cerium oxoperchlorate. The thermal decomposition of cerium(III) perchlorate hydrate at 460°C leads to formation of nanocrystalline cerium dioxide with particle size of 13 nm.     

Comprehensive evolved gas analysis (EGA) of amorphous precursors for S-doped titania by in situ TG–FTIR and TG/DTA–MS in air: Part 2. Precursor from thiourea and titanium(IV)-n-butoxide

Thermal decomposition of an amorphous precursor for sulfur-doped titania (S:TiO₂) nanopowders, prepared by controlled sol–gel hydrolysis-condensation of titanium(IV) tetrabutoxide and thiourea in aqueous butanol, has been studied in situ up to 850 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA–MS) and FTIR spectrometric gas cell (TG–FTIR) for analysis of gases and their evolution dynamics in order to explore and simulate thermal annealing processes of fabrication techniques aimed S:TiO₂ photocatalysts with photocatalytic activities under visible light.The studied S-doped precursor's decomposition course remembers to that of non-doped xerogel from Ti(IV)-n-butoxide, which seems to retard a considerable amount of organics in the solid phase even at high temperature, probably in polymeric forms, proven by evolution of CO₂ in several temperature regions of decomposition stages. The incorporation form of thiourea in the original xerogel seems to be chemically bounded, resulting lower decomposition temperature than that of pure thiourea, and producing evolution of carbonyl sulfide (COS) already between 120 and 190 °C. Nevertheless, evolution of SO₂, and that of CO₂ is also observed above 500 °C by both EGA detection methods. The latter observation implies that the blackish grey samples obtained even at 750 °C might be simultaneously S- and C-doped ones.