Thermal decomposition reactions of amminecobalt(III)complexes

Simultaneous TG-DTG-DTA studies under non-isothermal conditions on [Co(NH₃)₆]Cl₃, [Co(NH₃)₅]Cl₂ and [Co(NH₃)]₂(C₂O₄)₃.4H₂O complexes have been carried out in air and argon atmospheres in the temperature range 293–1273 K. All the dissociation processes occur in three main stages. The kinetics of thermal decomposition of the complexes have been evaluated from the dynamic weight loss data, to determine the most probably mechanisms of the stages on the basis of statistical analysis. The decomposition of the compounds was controlled by diffusion and phase boundary reactions except stage III of the oxalate complex in argon (random nucleation). The activation energiesE _a of the particular stages of the thermal decomposition were calculated.

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Zusammenfassung Simultane TG-DTG-DTA-Untersuchungen an den Komplexverbindungen [Co(NH₃)₆]Cl₃, [Co(NH₃)₅Cl]Cl₂ und [Co(NH₃)₆]₂(C₂O₄)₃.4H₂O unter nichtisothermen Bedingungen wurden in Luft und Argonatmosphäre bei 293–1273 K durchgeführt. Die Zersetzung läuft in jeweils drei Stufen ab. Für die kinetische Auswertung der thermischen Zersetzung der Komplexverbindungen aus den dynamischen Gewichtsabnahmekurven wurde der wahrscheinlichste Mechanismus der einzelnen Stufen mit Hilfe von statistischen Analysen ermittelt. Die Zersetzung der Komplexverbindungen wird meist durch Diffusions- und Phasengrenzreaktionen kontrolliert, nur bei der 3. Stufe des Oxalatkomplexes in Argon herrscht statistische Keimbildung. Die AktivierungsenergienE _a der einzelnen Zersetzungsstufen werden berechnet.

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293–1273 — [Co(NH₃)₆]Cl₃, [Co(NH₃)₅Cl]G₂ [Co(NH₃)₆]₂(C₂O₄)₃.4H₂O. . , . , III , . _a .

     

Thermal decomposition of some dihalotetramminecobalt(III) nitrates

The thermal decomposition of some dihalotetramminecobalt(III) nitrates [tetrammire =(NH₃)₄, (NH₃)₂(en), (NH₃)(dien), (en)₂, (pn)₂, (trien), etc.] with different degrees of chelation was studied by various thermoanalytical techniques. A partial oxidation—reduction was observed for these complexes above 200°C which was indicated by a rapid TG mass-loss and a large exothermic DTA peak. A relative order thermal stability is reported.     

Thermal decomposition of some biologically active complexes of ruthenium (III) with quinolone derivatives

A series of new complexes with mixed ligands of the type RuL₂(DMSO) _m Cl₃·nH₂O ((1) L: norfloxacin (nf), m = 1, n = 1; (2) L: ciprofloxacin (cp), m = 2, n = 2; (3) L: ofloxacin (of), m = 1, n = 1; (4) L: enrofloxacin (enro), m = 0.5, n = 4; DMSO: dimethylsulfoxide) were synthesised and characterised by chemical analysis and IR data. In all complexes both fluoroquinolone derivative and DMSO act as unidentate. The thermal behaviour steps were investigated in synthetic air flow. The thermal transformations are complex processes according to TG and DTG curves including dehydration, quinolone derivative and DMSO degradation respectively. The final product of decomposition is ruthenium (IV) oxide.     

Thermal decomposition of dinitrogen complexes of Cr(III)

The thermal behaviour of two dinitrogen complexes of chromium with EDTA and CDTA have been studied using DTA and TG. IR spectroscopy is used for the characterization of intermediate products. The loss of dinitrogen occurs at 240°C in both cases.     

The thermal decomposition of some Cr(III) complexes

The thermal decomposition reactions of the following chromium(III) complexes were investigated: Cr(CH₃COO)₃·2 H₂O, [C_r3O(CH₃COO)₆(H₂O)₃]Cl·2 H₂O and [Cr₃O(CH₂ClCOO)₆(H₂O)₃]Cl·6H₂O. Simultaneous TG/DTG/DTA were applied nonisothermal conditions. From the recorded curves, the activation energiesE _a were calculated for all the thermal decomposition steps. Appropriate chemical reactions were attributed to the thermal effects, with consideration to the X-ray diffraction and IR spectra results.

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Zusammenfassung Für die Untersuchung der thermischen Zersetzungsreaktion der Chrom(III)-Komplexe Cr(CH₃COO)₃·2H₂O [C_r3O(CH₃COO)₆·(H₂O)₃]Cl2H₂O und [C_r3O(CH₂ClCOO)₆·(H₂O)₃]C₁₆H₂O wurde simultane TG/DTG/DTA unter nichtisothermen Bedingungen eingesetzt. Ausgehend von den aufgezeichneten Kurven wurden für alle Schritte der Zersetzungsreaktion die E_a-Werte berechnet. In Übereinstimmung mit röntgenographischen und IR-spektroskopischen Ergebnissen wurden den thermischen Effekten passende chemische Reaktionen zugeordnet.

     

Thermal decomposition studies on manganese(III) selenito complexes

The heats of immersion of the systems B₂O₃P₂O₅ and Na₂OB₂O₃P₂O₅ in pyridine have been measured by the use of a solution microcalorimeter. In the composition range R R = atomic ratio, B/P) the heat of immersion was relatively small and was almost independent of R. The heat increased markedly with boron content in R > 1. The increase of heat qualitatively parallels that of surface acidity. Introduction of the Na₂O component reduced both heat of immersion and acidity. MgO was immersed in a benzene solution of benzoic acid. The heat of immersion increased with an increase of surface basicity.     

Thermal decomposition of complexes of antimony(III) bromide with hydrobromides of some aromatic amines

Thermal studies have been carried out on crystalline complexes formed between antimony(III) bromide and hydrobromides of some aromatic amines in concentrated hydrobromic acid solutions. Thermal analysis curves of the compounds under study are presented. Kinetic parameters of the thermal decomposition reactions were calculated from the TG curves using the Horowitz—Metzger method. A comparison of the thermal stabilities of the complexes was made.     

Kinetics of thermal decomposition of iron(III) dicarboxylate complexes

Summary Tris(dicarboxylate) complexes of iron(III) with oxalate, maleate, malonate and phthalate viz. K₃[Fe(C₂O₄)₃]×3H₂O (1), K₃[Fe(OOCCH₂COO)₃]×3H₂O (2), K₃[Fe(OOCCH=CHCOO)₃]×3H₂O (3), K₃[Fe(OOC-1,2-(C₆H₄)-COO)₃]×3H₂O (4) have been synthesized and characterized using a combination of physicochemical techniques. The thermal decomposition behaviour of these complexes have been investigated under dynamic air atmosphere upto 800 K. All these complexes undergo a three-step dehydration/decomposition process for which the kinetic parameters have been calculated using Freeman-Carrol model as well as using different mechanistic models of the solid-state reactions. The trisoxalato and trismalonato ferrate(III) complexes undergo rapid dehydration at lower temperature below 470 K. At moderately higher temperatures (i.e. >600 and 500 K, respectively) they formed bis chelate iron(III) complexes. The trismalonato and trismaleato complexes dehydrate with almost equal ease but the latter is much less stable to decomposition and yields FeCO₃ below 760 K. The cis-dicarboxylate complexes particularly with maleate(2-) and phthalate(2-) ligands are highly prone to the loss of cyclic anhydrides at moderately raised temperatures. The thermal decomposition of the tris(dicarboxylato)iron(II) to iron oxide was not observed in the investigated temperature range up to 800 K. The dehydration processes generally followed the first or second order mechanism while the third decomposition steps followed either three-dimensional diffusion or contracting volume mechanism.     

Thermal decomposition of Cr(III) complexes with urea and thiourea

The thermal decompositions of Cr(III) complexes with urea and thiourea were investigated. The courses of the decompositions were found to be anion- and ligand-dependent. Suggestions for a mechanism of decomposition of these complexes are presented. The final product of decomposition of the complexes investigated was chromium(III) oxide (Cr₂O₃).

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Zusammenfassung Die thermische Zersetzung der Komplexe von Cr(III) mit Karbamid und Thiokarbamid wurde untersucht. Der Verlauf der Zersetzung wurde für Anionen- und Liganden-abhängig gefunden. Vorstellungen über eine mechanische Zersetzung dieser Komplexe werden gegeben. Das Endprodukt der Zersetzung der untersuchten Komplexe war jeweils Chrom(III)oxid (Cr₂O₃).

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Résumé On a étudié la décomposition thermique des complexes du chrome(III) avec l'urée et la thiourée. On a trouvé que le processus de la décomposition dépend de l'anion et du ligand. On propose un mode de décomposition mécanique pour ces complexes. Le produit final de la décomposition des complexes étudiés est l'oxyde de chrome(III), Cr₂O₃.

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Cr (111) . , . . (111) (Cr₂O₃).

     

Thermal behaviour of some crystal solvates of magnanese(III) complexes

The thermal behaviour of some crystal solvates of square pyramidal Mn(III) complexes has been studied. The nature of interaction of the water of crystallization has been clarified, and a correlation was found between the hardness of the axial anions and the desolvation temperatures. The decomposition pathways of the investigated complexes have also been discussed.

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Thermisches Verhalten einiger Kristallsolvate von Mangan(III)-Komplexen

Zusammenfassung Es wurde das thermische Verhalten einiger Kristallsolvate von quadratischpyramidalen Mangan(III)-Komplexen untersucht. Die Natur der Wechselwirkung des Kristallwassers wurde geklärt und eine Korrelation zwischen der Härte der axialen Anionen und der Solvatationstemperatur gefunden. Der Verlauf der thermischen Zersetzung der Komplexe wird ebenfalls diskutiert.

     

Thermal analysis of some chromium(III) complexes with dicarboxylic ligands

The solid chromium(III) complexes with a series of dicarboxylic ligands were prepared as potassium salts and examined by TG, DTG and DSC. The results are discussed in terms of basicity by arranging the ligands in proper series.     

Thermal decomposition of bis(dimethylglyoximate) iron(II) complexes containing axial N-heterocyclic ligands

A systematic TG and DTG study of the thermal decomposition of a series of bis(dimethylglyoximate)iron(II) complexes containing axial N-heterocyclic ligands is reported. The decomposition reaction is very exothermic, coinciding with the loss of the axial ligands. The average temperatures of decomposition correlate linearly with the basicity properties of the axial ligands.

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Zusammenfassung Es wird eine systematische TG- und DTA-Untersuchung der thermischen Zersetzung einer Reihe von Bis(dimethylglyoximat)-Komplexe von Eisen(II) mit axialem N-heterocyclischen Liganden beschrieben. Die Zersetzungsreaktion ist sehr exotherm, was mit dem Verlust der axialen Liganden zusammenfällt. Die durchschnittliche Zersetzungstemperatur ist den Basizitäts eigenschaften der axialen Liganden proportional.

     

Electron paramagnetic resonance characteristics of some non-heme low-spin iron(III) complexes

We have recorded the powder EPR-spectra of some near octahedral iron(III) complexes with tridentate ligands donors and analysed their spectra with simple ligand field analysis and for some cases with the angular overlap model (AOM). We have determined the electron praramagnetic resonance (EPR) characteristic of bis 1,4,7-triazacyclonane iron(III)chloride at 4 K and found that it was similar to the characteristics of the so-called 'highly anisotropic low spin' complexes. We have recorded the powder spectra of bis (2,6-bis(benzimidazoly-2-yl)pyridine) iron(III) perchlorate and made an AOM-analyses of the structural similar complex bis-(2,6 (N-carbamoyl)-pyridine) iron(III). With a combination of ligand field analyses and AOM, we could determine the pi-donor properties of these ligands. The same approach have been used to determine the pi-donor properties of the hydroperoxo ligand. Finally we have recorded the powder EPR-spectrum of [Fe(CN)6]3- doped in K3[Co(CN)6] and [Co(NH3)6][Co(CN)6] at 4 and 100 K and in water at 4 K. The spectra are interpreted as the effect of a dynamic Jahn-Teller distortion.     

Thermal studies on oxalate complexes. II. Complexes of iron (III) and chromium (III)

The decomposition of solid K₃[Fe(C₂O₄)₃] · 2 H₂O and K₃[Cr(C₂O₄)₃] · 3 H₂O has been studied using TGA and DSC. After dehydration, the chromium compound was found to decompose by the loss of CO in two steps, the loss of CO₂ and additional CO, and finally the loss of CO₂. The final product appears to be either K₃CrO₃ or the mixed oxides of chromium and potassium. Kinetic parameters and enthalpy data are presented for these reactions. In the case of K₃[Fe(C₂O₄)₃] · 2 H₂O, dehydration is followed by the loss of CO₂ and CO, CO₂ alone, and finally CO. The final product appears to be a basic carbonate of the type K₃[FE(O)₂(CO₃)]. Kinetic and thermal data are presented for most of these decomposition reactions.     

Thermal decomposition of metal complexes V. Lanthanide(III) complexes of benzo-15-crown-5

Thermal dissociation reactions of lanthanide(III) nitrates and thiocyanates solid complexes of the cyclic polyether benzo-15-crown-5 were studied in dynamic atmosphere of dry nitrogen and under reduced pressure (5·10^?2 mm Hg). The complexes of lanthanide nitrates undergo dissociation with ligand decomposition while from those of lanthanide thiocyanates the ligand is released undecomposed. Values of enthalpy change and “activation energy” for the dissociation reactions of the complexes with lanthanide thiocyanate were obtained and briefly discussed.     

Thermal decomposition of metal complexes IV. Lanthanide(III) complexes with dibenzo-18-crown-6

The solid-state thermal dissociation reactions of the complexes of all the lanthanide(III) nitrates and thiocyanates (except Pm) with the cyclic polyether dibenzo-18-crown-6 were investigated. Thermal analysis was carried out in a dynamic atmosphere of dry nitrogen and under reduced pressure (5·10^?2 mm Hg). In both the conditions examined, the two series of complexes exhibit different thermal behaviours. The values of enthalpy change and “activation energy” for the dissociation reactions of the complexes with lanthanide thiocyanates show a periodic trend along the lanthanide series.     

Thermal decomposition of ammonium fluoromanganates(III)

The thermal decomposition of ammonium fluoromanganates (III) has been investigated in air and argon by simultaneous thermogravimetry and differential thermal analysis. Chemical analysis, X-ray powder data, and infrared spectra have been employed to characterise the intermediate and final products. The thermal decomposition can be described by the sequence (NH₄₃MnF₆ → (NH₄)₂MnF₅ → NH₄MnF₄ → MnF₂. Although penta- and tetra-fluoromanganates are well-defined compounds, the intermediate states could not be separated. In addition, a high temperature form of ammonium hexafluoromanganate has been observed.     

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.     

Thermal decomposition of tris(N,N-disubstituted dithiocarbamate) complexes of As(III), Sb(III) and Bi(III)

Thermal studies on tris(N,N-disubstituted dithiocarbamates) of arsenic(III), antimony(III) and bismuth(III) of the type M[S₂CX]₃ (M=As, Sb, Bi; X=NEt₂, N(CH₂)₄O) by simultaneous TG, DTG and DTA were carried out in air and nitrogen atmospheres. The apparent activation energies were determined by the graphical method of Freeman-Carroll, modified forn=1, and Piloyan's two methods from the TG and DTG curves. The TTN temperatures were calculated from the TG profiles.A possible mechanism of the decomposition reaction is suggested on the basis of the results of their pyrolysis and their mass spectral data.The intermediates obtained at the ends of various decomposition stages were identified via elemental analysis and i. r. and mass spectral data, whereas the residues were identified by X-ray powder diffraction analysis. A dimeric structure of the type M₂[S₂CN(CH₂)₄O]₄ (M=As, Sb) is proposed.

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Zusammenfassung N,N-Disubstituierte Tris-dithiocarbaminate von Arsen(III), Antimon(III) und Wismut(III) des Typs M[S₂CX]₃ (M=As, Sb, Bi; X=NEt₂, N(CH₂)₄O) wurden simultan mittels TG, DTG und DTA in Luft- und StickstoffatmosphÄre untersucht. Die scheinbaren Aktivierungsenergien wurden nach der fürn=1 modifizierten graphischen Methode von Freemann-Carroll und nach den zwei Methoden von Piloyan aus den TG- und DTG-Kurven ermittelt. Die TTN-Temperaturen wurden aus den TG-Profilen berechnet. Ein möglicher Zersetzungsmechanismus wird basierend auf Ergebnissen der Pyrolyse und massenspektrometrischen Daten vorgeschlagen. Die nach den verschiedenen Zersetzungsstufen vorliegenden Zwischenprodukte wurden mittels Elementaranalyse sowie infrarot- und massenspektrometrischen Daten, der Rückstand durch Röntgenpulverdiffraktometrie identifiziert. Es wird eine dimere Struktur des Typs M₂[S₂CN(CH₂)₄O)₄ (M=As, Sb) vorgeschlagen.

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(N,N- ) , M[S₂CX]₃, M=As, Sb, Bi; a X=NEt₂, N(CH₂)₄O, , . —, n=1, . . - , . , , , , — - . M₂[S₂CN(CH₂)₄O]₄, M=As, Sb.

     

Thermal decomposition of hexamminecobalt(III) chloride

The results of comparative thermal analysis (TG-DTG-DTA-DSC) of the thermal decomposition of hexamminecobalt(III) chloride in air atmosphere are reported. The kinetics and mechanism of the thermal decomposition, the process enthalpy and the variation in specific thermal capacity of the solid product reaction with temperature were determined.