Thermal decompositions of formates. Part IV. Thermal dehydrations of Mg(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) formate dihydrates

The thermal dehydrations of formate dihydrates of Mg(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) were studied by means of thermogravimetry, differential thermal analysis and differential scanning calorimetry in air.The reaction orders of dehydration obtained by the dynamic and the static methods were found to be 2/3 for all the salts examined, which indicated that the rate of dehydration was controlled by a chemical process at a phase boundary. This was confirmed by microscopic observation.The values of activation energy, frequency factor and the enthalpy change of dehydration for all salts examined, were 21–30 kcal mole^?1, 10¹⁰-10¹² sec^?1 and 28–31 kcal mole^?1, respectively.The temperature at which the dehydration occurred was regarded as a measure of the strength of the metalOH₂ bond, and this temperature increased with increasing the reciprocal of the radius of the metallic ion.     

Thermal decompositions of zinc(II) benzenedicarboxylates

The thermal decompositions of zinc(II)benzenedicarboxylates were studied in air atmosphere at a heating-rate of 10 deg min^–1. Zinc phthalate and isophthalate were dehydrated in one step and next decomposed directly to ZnO. Zinc terephthalate was dehydrated in two steps and then decomposed directly to ZnO.

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Zusammenfassung Bei einer Aufheizgeschwindigkeit von 10°-min^–1 wurde die thermische Zersetzung von Zink(II)benzoldikarboxylat in Luft untersucht. Zinkphtalat und -isophtalat wird zunächst in einem Schritt dehydratisiert und anschließend zu ZnO zersetzt. Zinkterephtalat wird vor der endgültigen Zersetzung zu ZnO in zwei Schritten dehydratisiert.

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10 / . - . , .

     

Thermal decomposition of Co(II), Ni(II), Cu(II) and Zn(II) hippurates

The hippurates of Co(II), Ni(II), Cu(II) and Zn(II) were isolated from the solution, their quantitative composition and the way of coordination of metal — ligand were determined and the conditions and products of thermal decomposition during heating in air atmosphere up to 1273 K were studied. The complexes of Ni(II), Cu(II) and Zn(II) heated lose some water molecules and then decompose to MO. The hippurate of Co(II) heated loses some water molecules and then decomposes to CoO with intermediate formation Co₃O₄.

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Zusammenfassung Aus Lösung wurden die Co(II)-, Ni(II)-, Cu(II)- und Zn(II)-Salze der Hippursäure gewonnen, ihre quantitative Zusammensetzung sowie die Art der Koordination der Metall-Ligandenbindung bestimmt. Weiterhin wurden die Bedingungen und Produkte der thermischen Zersetzung beim Erhitzen in einer Luftatmosphäre bis 1273 K untersucht. Die Komplexe von Ni(II), Cu(II) und Zn(II) verlieren beim Erhitzen ein paar Moleküle Wasser und zersetzen sich anschlieend zu MO. Co(II)-hippurat gibt beim Erhitzen einige Moleküle Wasser ab und zersetzt sich dann über die Zwischenstufe Co₃O₄ zu CoO.

     

Thermal Decomposition of Bi(III), Cd(II), Pb(II) and Cu(II) Thiocyanates

Thermal decomposition of Bi(SCN)₃, Cd(SCN)₂, Pb(SCN)₂ and Cu(SCN)₂ has been studied. The thermal analysis curves and the diffraction patterns of the solid intermediate and final products of the pyrolysis are presented. The gaseous products of the decomposition (SO₂ and CO₂) were detected and quantitatively determined. Thermal, X-ray and chemical analyses have been used to establish the nature of the reactions occurring at each stage in the decomposition.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermal behaviour of Co(II), Ni(II), Cu(II), Zn(II), Hg(II) and Pd(II) complexes with isatin-β-thiosemicarbazone

The isatin-β-thiosemicarbazone (ITC) complexes of Co(II), Ni(II), Cu(II), Zn(II), Hg(II) and Pd(II) were prepared and characterized by elemental analysis, as well as molar conductivity, magnetic susceptibility, FTIR, UV-Vis and ¹H NMR spectroscopic methods. The complexes were also studied for its thermal stability. They all behaviour as anhydrous complexes and its thermolysis passes through the stages of deamination (517–547 K) and complete thermal decomposition (619–735 K).     

Spectral and Thermal Studies of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) Complexes with 3-methylglutaric Acid

Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 3-methylglutarates were prepared as solids with general formula MC₆ H₈ O₄ ×n H₂ O, where n =0–8. Their solubilities in water at 293 K were determined (7.0×10⁻² −4.2×10⁻³ mol dm⁻³ ). The IR spectra were recorded and thermal decomposition in air was investigated. The IR spectra suggest that the carboxylate groups are mono- or bidentate. During heating the hydrated complexes lose some water molecules in one (Mn, Co, Ni, Cu) or two steps (Cd) and then mono- (Cu) or dihydrates (Mn, Co, Ni) decompose to oxides directly (Mn, Cu, Co) or with intermediate formation of free metals (Co, Ni). Anhydrous Zn(II) complex decomposes directly to the oxide ZnO. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal and Spectral Characterization of 5-Cholro-2-methoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)

The thermal stabilities of 5-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) were studied in air and nitrogen atmospheres. The complexes were obtained as mono-, di-, tetra-and pentahydrates with a metal to ligand ratio of 1:2 and with colours typical for M²⁺ ions (Mn-slightly pink, Co-pink, Ni-green, Cu-blue and Zn-white) and as polycrystalline compounds. When heated they dehydrate to form anhydrous salts which nextare decomposed to the oxides of the respective metals in air while in nitrogen to the mixtures of metal oxides and oxychlorides and carbon. The most thermally stable in air, nitrogen and argon atmospheres is 5-chloro-2-methoxybenzoate of Cu(II) while the least thermally stable is that of Co(II). This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition kinetics of Co(II), Ni(II), Cu(II) and Zn(II) complexes of dihydrazinium ethylenediamine-tetraacetate

Hydrazinium ethylenediaminetetraacetatometalate complexes of the type, N₂H₅ [M(Hedta)·H₂O] were subjected to systematic TG/DTG analysis. The decomposition process consists of three stages. Kinetic parameters were evaluated for each of these stages using the Coats-Redfern equation.     

Thermal decomposition of mixed ligand complexes of manganese(II), nickel(II), copper(II), zinc(II) and cadmium(II) containing triethanolamine and oxalate

The kinetics of thermal decomposition of mixed ligand complexes of Mn(II), Ni(II), Cu(II), Zn(II) and Cd(II) containing triethanolamine and oxalate have been studied using thermogravimetry (TG) and differential scanning calorimetry (DSC). The decomposition reaction in which the complexes lose one molecule of triethanolamine was found to be first order and the activation energy and pre-exponential factors were calculated using established techniques. The values of E_a obtained for these reactions using a modified form of the Horowitz and Metzger equation were 27.75, 20.54, 18.33, 25.32 and 23.25 kcal mole^?1, respectively. Infrared spectral data of these complexes and the intermediates gave additional information about the coordinating nature of the ligands in these complexes.     

Thermal stability and photostability of water solutions of sulfophthalocyanines of Ru(II), Cu(II), Ni(II), Fe(III) and Co(II)

The thermal and photochemical stabilities were investigated for tetrasulfophthalocyanines of Cu, Co, Ni, Fe and Ru (MPcS) and for two monosulfophthalocyanines of Ru, either without (RuPcS1) or with the coordination of two units of DMSO in apical positions ([RuPcS1(DMSO)₂]DMSO). The thermal degradation of all of the studied complexes never showed the formation of spectroscopically detectable intermediates. CuPcS was the most stable complex, while all of the Ru-sulfophthalocyanines were particularly prone to thermal degradation. Photodegradation showed a better selectivity, and as with thermal degradation, the order of reactivity goes from the most stable CuPcS, to the least stable Ru-sulfophthalocyanines (RuPcS, RuPcS1 and [RuPcS(DMSO)₂]DMSO). In particular, when the RuPcS complex was irradiated, a stable intermediate was detected that had an absorption band at 532 nm and a mass spectrum attributable to the tetrasulfophthalocyanine from oxidative ring cleavage by the action of the singlet oxygen formed via ¹*RuPcS photosensitization. The most probable molecular formula demonstrates a new complex, with a cleaved ring containing an -NO group and two -OH groups that are all bonded at the two extremities of the open-chain molecule.     

Preparation,Properties and Thermal Decompositions of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) Complexes of 2,5-dichlorobenzoic Acid

Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 2,5-dichlorobenzoates were prepared and their compositions and solubilities in water at 295 K were determined. The IR spectra and X-ray diffractograms of the obtained complexes were recorded. The complexes of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) were obtained as solids with a 1:2 molar ratio of metal to organic ligand and different degrees of hydration. When heated at a heating rate of 10 K min^-1, the hydrated complexes lose some (Co, Zn) or all (Ni, Cu, Cd) of the crystallization water molecules and then decompose to oxide MO (Co, Ni) or gaseous products (Cu, Zn, Cd). When heated at a heating rate of 5 K min^-1, the complexes of Ni(II) and Cu(II) lose some (Ni) or all (Cu) of the crystallization water molecules and then decompose directly to MO. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal analysis of cobalt(II), nickel(II), copper(II) and zinc(II) bis (3,5-dimethyl-1-pyrazolyl)dihydroborates

Complexes of general formula M[H₂B(Me₂pz)₂]₂, [where M = Co(II), Ni(II), Cu(II), and Zn(II)] are characterized by thermal analysis and complementary techniques. Mixtures of boron and metal oxides are found as final residues. Relative thermal stability (Ni > Cu > Co = Zn) and thermal behaviour are discussed. Melting and sublimation data are compared with those referred to in the literature.     

Thermal decomposition kinetics of vanillidene anthranilic acid complexes of cobalt(II), nickel(II), copper(II) and zinc(II)

The thermal decomposition of cobalt(II), nickel(II), copper(II) and zinc(II) complexes of the Schiff base vanillidene anthranilic acid was studied by TG. The chelates show somewhat similar TG plots when heated in an atmosphere of air. Thermoanalytical data (TG and DTG) of these chelates are presented in this communication. Interpretation and mathematical analysis of these data and evaluation of order of reaction, the energy and entropy of activation based on the differential method employing the Freeman-Carroll equation, the integral method using Coats-Redfern equation and the approximation method using the Horowitz-Metzger equation are also given. On the basis of experimental findings in the present course of studies, it is concluded that the relative thermal stability of vanillidene anthranilic acid chelates can be aligned as Co(II)Ni(II)>Zn(II)>Cu(II).

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Zusammenfassung Die thermische Zersetzung von Cobalt(II)-, Nickel(II)-, Kupfer(II)- und Zink(II)-Komplexen der Schiffschen Base Vanillidenanthranilsäure wurde thermogravimetrisch untersucht. Die Chelate zeigen in einer Luftatmosphäre ähnliche TG-Kurven. Thermoanalytische Daten (TG and DTG) dieser Chelate werden mitgeteilt, interpretiert und mathematisch analysiert. Ebenfalls werden die Reaktionsordnung und die Energie und Entropie der Aktivierung nach der von Freeman-Carroll angewandten differentiellen Methode, nach der auf der Coats-Redfern-Gleichung basierenden integralen Methode und nach der die Horowitz-Metzger Gleichung benutzenden Näherungsmethode bestimmt. Aus den Befunden wird geschlossen, dass die thermische Stabilität von Vanillidenanthranilsäure-Chelaten in der Reihenfolge Co(II)Ni(II)>Zn(II)> >Cu(II) abnimmt.

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, , . - . . , , - , , - . , Ni>Zn>u.

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We thank Dr. C. P. Savariar, Professor of Chemistry, University of Calicut for encouragement. We are also grateful to the University Grants Commission for the award of a Senior Research Fellowship to one of us (J. C).     

Synthesis and Thermal Properties of 4,4'-bipyridine Adducts of Mn(II), Co(II), Ni(II) and Cu(II) Monochloroacetate

The complexes with the empirical formula M(4-bipy)(ClCH₂COO)₂ ×nH₂O (where: 4-bipy=4,4'-bipyridine, L=ClCH₂ COO^–, M (II)=Mn, Co, Ni, Cu) were prepared and characterized via the IR and electronic (VIS) spectra and conductivity measurements. Thermal decomposition of these compounds was studied. During heating in air dehydration processes occur. The anhydrous compounds decompose at high temperature to oxides. The principal volatile mass fragments correspond to: H₂O, CO₂, CH₃Cl, HCl, Cl₂ and other. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal study of Cu(II), Ni(II) and Pd(II) chelates of resacetophenoneoxime

Summary Thermal analysis of resacetophenoneoxime and its chelates of Cu(II), Ni(II) and Pd(II) is carried out. A comparison is made between the thermal stability and the solution stability of chelates and found that they oppose each other. The thermal stability for the chelates studied is PdNi>Cu and the solution stability on the other hand is Pd>Cu>Ni. The results obtained were compared with the data available in the literature for structurally similar oximes. The advantages of the reagent for gravimetric and thermogravimetric analysis of metal ions were discussed.

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Thermochemische Untersuchung der Cu(II)-, Ni(II)- und Pd(II)-Chelate von Resacetophenonoxim

Zusammenfassung Die thermische Stabilität der Chelate und ihre Stabilität in Lösung wurden verglichen und festgestellt, daß diese sich nicht entsprechen. Die erste nimmt ab in der Reihenfolge PdNi>Cu, die zweite in die Reihenfolge Pd>Cu>Ni. Die erhaltenen Ergebnisse wurden denen aus der Literatur für strukturell ähnliche Oxime gegenübergestellt. Die Vorteile des Reagenses für gravimetrische und thermogravimetrische Bestimmungen werden diskutiert.

     

Thermal behaviour of xanthinium salts of Zn(II), Cd(II) and Hg(II)

Salts [XanH⁺]₂[MCl ₄ ^2- ] (where XanH⁺=protonated form of xanthine and M=Zn(II), Cd(II) and Hg(II) have been synthesized and studied by IR,¹H-NMR, TG and DSC. The metal is not coordinated to the ligand and forms a salt-like structure. The cationic proton is on N(7). Thermal decomposition of these salts occurs in two steps: (i) dehalogenation and (ii) decomposition. Dehalogenation enthalpies have been calculated from DSC curves.

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Zusammenfassung (XanH⁺)₂(MCl ₄ ^2- )-Salze (worin XanH⁺ die protonisierte Form von Xanthin bedeutet und M=Zn(II), Cd(II) oder Hg(II) ist) wurden synthetisiert und mit IR,¹H-NMR, TG und DSC untersucht. In diesem Fall liegt keine Koordination des Metalls mit dem Liganden vor, und es bildet sich eine salzartige Struktur aus. Das kationische Proton ist an N(7) lokalisiert. Die thermische Zersetzung dieser Salze erfolgt in zwei Schritten: (i) Dehalogenisierung und (ii) Zersetzung. Dehalogenierungsenthalpien wurden aus DSC-Kurven berechnet.

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- -, [XanH⁺]₂[MCl ₄ ^2– ], XanH⁺ — , M — , . , . . : . - .

     

Study of the Thermal Decompositions on N,N-Dialkyl-N'-Benzoylthiourea Complexes of Cu(II), Ni(II), Pd(II), Pt(II), Cd(II), Ru(III) and Fe(III)

The thermal decompositions of the complexes of N,N-dialkyl-N'-benzoylthioureas with Cu(II), Ni(II), Pd(II), Pt(II), Cd(II), Ru(III) and Fe(III) were studied by TG and DTA techniques. These metal complexes decompose in two stages: elimination of dialkylbenzamide, and total decomposition to metal sulphides or metals. The influence of the alkyl substituents in these benzoylthiourea chelates on the thermal behaviour of the metal complexes was investigated.This revised version was published online in November 2005 with corrections to the Cover Date.     

Synthesis and Thermal Decomposition of Mixed 2,4'-bipyridine-oxalato Complexes With Mn(II), Co(II), Ni(II) and Cu(II)

The mixed 2,4'-bipyridine-oxalato complexes of the formulae M(2,4'-bipy)₂ C₂ O₄ 2H₂ O (M (II)=Mn, Co, Ni, Cu; 2,4'-bipyridine=2,4'-bipy or L ; C₂ O^2– ₄ =ox) have been prepared and characterized. IR data show that the 2,4'-bipy coordinated with these metals(II) via the least hindered (4')N atom; that oxalate group acts as bidentate chelating ligand. Room temperature magnetic moments are normal for the orbital singlet states. The thermal decomposition of these complexes was investigated by TG, DTA and DTG in air. The endothermic or exothermic character of the decomposition of ML₂ (ox)2H₂ O was discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal, spectral and magnetic behaviour of 2,3,4-trimethoxybenzoates of Mn(II), Co(II), Ni(II) AND Cu(II)

Four new complexes of 2,3,4-trimethoxybenzoic acid anion with manganese(II), cobalt(II), nickel(II) and copper(II) cations were synthesized, analysed and characterized by standard chemical and physical methods. 2,3,4-Trimethoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) are polycrystalline compounds with colours typical for M(II) ions. The carboxylate group in the anhydrous complexes of Mn(II), Co(II) and Ni(II) is monodentate and in that of Cu(II) monohydrate is bidentate bridging one. The anhydrous complexes of Mn(II), Co(II) and Ni(II) heated in air to 1273 K are stable up to 505–517 K. Next in the range of 505–1205 K they decompose to the following oxides: Mn₃O₄, CoO, NiO. The complex of Cu(II) is stable up to 390 K, and next in the range of 390–443 K it loses one molecule of water. The final product of its decomposition is CuO. The solubility in water at 293 K is of the order of 10^–3 mol dm^–3 for the Mn(II) complex and 10^–4 mol dm^–3 for Co(II), Ni(II) and Cu(II) complexes. The magnetic moment values of Mn²⁺, Co²⁺, Ni²⁺ and Cu²⁺ ions in 2,3,4-trimethoxybenzoates experimentally determined in the range of 77–300 K change from 5.64–6.57 μB (for Mn²⁺), 4.73–5.17 μB (for Co²⁺), 3.26–3.35 μB (for Ni²⁺) and 0.27–1.42 μB (for Cu²⁺). 2,3,4-Trimethoxybenzoates of Mn(II), Co(II) and Ni(II) follow the Curie–Weiss law, whereas that of Cu(II) forms a dimer.