Thermal decomposition of rubidium-sodium halidothiocyanatobismuthates(III)

Mono- and binuclear rubidium-sodium halidothiocyanatobismuthates(III) have been prepared. Thermal, chemical and X-ray analyses were used to establish the thermal decomposition course of these complexes. The pyrolysis occurs in three stages connected with the mass loss and exothermic effects. The decomposition temperatures of the title salts are 190–210°C.     

Thermal properties of rhodium(III) chloride

Thermal decomposition of rhodium(III) chloride under inert, oxidative and reductive gas atmospheres was investigated in order to determine its thermal properties. Stoichiometries of the reactions occurring during heating are described. it is suggested that the chemical formula of soluble rhodium(III) chloride should be presented as RhCl₃·HCL·xH₂O. Cold crystallisation of anhydrous rhodium(III) chloride at a temperature of about 500°C was established. The procedure for quantitative determination of volatile matter (water and hydrochloric acid) content and rhodium content by thermogravimetry is given and discussed. The repeatability and reproducibility of the method are estimated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Lanthanum(III) chloride complexes with heterocyclic Schiff bases

Condensation of 2-amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene with carbonyl compounds such as isatin, o-hydroxyacetophenone or benzoin in 1:1 ratio in ethanol medium yielded three distinctly different heterocyclic Schiff bases viz. 2-(N-indole-2-one)amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene (ISAT), 2-(N-o-hydroxyacetophenone)amino- 3-carboxyethyl-4,5,6,7-tetrahydro-benzo[b]thiophene (HAAT) or 2-(N-benzoin)amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene (HBAT) respectively. These ligands formed well defined complexes with lanthanum(III) chloride under suitable conditions. The ligands and the complexes have been characterized on the basis of elemental analyses, molar conductance measurements, UV-visible, IR and proton NMR spectral studies. Kinetics and mechanism of the thermal decomposition of the ligands and the metal complexes have been studied using non-isothermal thermogravimetry. Kinetic parameters were calculated for each step of the decomposition reactions using Coats-Redfern equation. The rate controlling process for all the ligands and complexes is random nucleation with the formation of one nucleus on each particle (Mampel equation). Relative thermal stabilities of the ligands and the metal complexes have been compared.     

Thermal and spectroscopic studies of terbium(III) and dysprosium(III) complexes with piperidin-4-ones

Terbium(III) and dysprosium(III) nitrate complexes with variously substituted 2,6-diphenylpiperidin-4-ones (L¹)-(L¹⁰) of general formula [Ln(L)(NO₃)₂(H₂O)₂]NO₃ have been synthesized. These complexes have been characterized by analytical, spectral and thermal studies. Molar conductance data show that these complexes are 1:1 electrolytes. The presence of two coordinated water molecules is confirmed by thermal and infrared spectral studies. IR spectral data indicate that piperidin-4-ones, in spite of having two coordinating sites, are monodentate, coordinating only through ring nitrogen. The IR and conductance data reveal the presence of two bidentate and one ionic nitrate groups. The nephelauxetic ratio (β), covalency factor (b^1/2) and Sinha’s parameter (δ) evaluated from electronic spectral data of dysprosium(III) complexes indicate a little covalency in metal-ligand bonding.     

Thermogravimetric and spectroscopic studies on La(III) and Ce(III) complexes with some thio-schiff bases

Solid complexes of five derivatives of thio-Schiff bases with La(III) and Ce(III) ions were prepared and characterized by elemental and thermogravimetric analyses. The suggested general formula of the solid complexes is [ML₂(H₂O)X]·2H₂O, whereM=trivalent lanthanide ion,L=Schiff base andX=Cl^? or ClO ₄ ^? . Information about the water of hydration, the coordinated water molecules, the coordination chemistry and the thermal stability of these complexes was obtained and is discussed. Additionally, a general scheme of thermal decomposition of the lanthanide-Schiff base complexes is proposed.     

Thermal decomposition of chromium(III) nitrate(V) nanohydrate

Thermal decomposition of Cr(NO₃)₃·9H₂O in helium and in synthetic air was studied by means of TG, DTA, EGA and XRD analysis. The dehydration occurs together with decomposition of nitrate(V) groups. Eight distinct stages of reaction were found. Intermediate products of decomposition are hydroxy- and oxynitrates containing chromium in hexa- and trivalent states. The process carried out in helium leads to at about 260°C and in air is formed at about 200°C. The final product of decomposition (>450°C) is Cr₂O₃, both in helium and in air. This revised version was published online in July 2006 with corrections to the Cover Date.     

Complexes of Oxamic Acid with La(III), Gd(III), Tb(III), Er(III), Tm(III) and Lu(III)

The preparation, for the first time, of the deprotonated complexes of oxamic acid with La(III), Gd(III), Tb(III), Er(III), Tm(III) and Lu(III) is reported. Analytical results, conductometric measurements, magnetic moments and spectral data (IR and diffuse reflectance spectra) are discussed in terms of possible structural types. The oxamate anion acts as a N, O bidentate non-bridging ligand.     

Thermal decomposition of scandium(III) 2-chloro-, 30chloro, 4-chloro- and 2,4-dichlorobenzoates in an air atmosphere

The conditions of thermal decomposition of hydrated scandium(III) chlorobenzoates were studied. On heating, the carboxylates decompose in many steps. The hydrated complexes first lose water of crystallization in one or two steps and then anhydrous compounds are transformed to Sc₂O₃ with formation of Sc₂O(CO₃)₂ intermediate. The dehydration of the complexes is accompanied by an endothermic effect and the decomposition of anhydrous complexes by strong endothermic effects. The anhydrous complexes are melted at 255–300°C.     

Thermal Deamination-anation in Cobalt(III) Thiocyanate Complexes. Novel decarbonylation of the equatorial amide ligand

The solid state thermal behavior of trans-[Co(bpb)(amine)₂]NCS⋅H₂O complexes where (bpb)=[N,N’-bis(2-pyridinecarboxamido-N)-1,2-benzene], and amine=pyrrolidine (prldn)(1), and benzylamine (bzlan) (2), and trans-[Co(bpb)(piperidine)₂]ClO₄⋅H₂O (3) (mixed with KSCN), has been studied using thermoanalytical techniques, infrared spectroscopy, and pyrolysis coupled to both infrared and mass spectrometry, PY/FTIR and PY/MS. The deamination-anation reaction is clearly observed for all three complexes. The estimated values of E _a for the deamination-anation are: E _a(1)=246.8 kJ mol⁻¹, E _a(2)=255.7 kJ mol⁻¹, E _a(3)=234.7 kJmol⁻¹. The trend in E _a values is rationalized based on the ligand field strength of the amines and the structural effects. A novel decarbonylation of the amide CO group from the equatorial ligand is observed after the release of one amine molecule. This process has been monitored for complex (1) by FTIR in the carbonyl region and by mass spectrometry for the detection of CO₂ at 280°C. The activation energy of this process is estimated for complex (1) (662.5 kJ mol⁻¹). The reaction scheme for the observed reactions is proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Complex formation constants and thermodynamic parameters for La(III) and Y(III)L-serine complexes

Summary The stoichiometric stability constants for La(III) and Y(III)L-serine complexes were determined by potentiometric methods at different ionic strengths adjusted with NaClO₄ and at different temperatures. The overall changes in free energy (G ^o), enthalpy (H ^o), and entropy (S ^o) during the protonation ofL-serine and that accompanying the complex formation with the metal ions have been evaluated.

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Komplexbildungskonstanten und thermodynamische Parameter für La(III)- und Y(III)-L-Serin-Komplexe

Zusammenfassung Die stöchiometrischen Komplexbildungskonstanten für La(III)- und Y(III)-L-Serin-Komplexe wurden mittels potentiometrischer Methoden bei verschiedenen Ionenstärken (mit NaClO₄ adjustiert) und bei verschiedenen Temperaturen bestimmt. Die Änderungen in der freien Energie (G ^o), Enthalpie (H ^o) und Entropie (S ^o) während der Protonierung und der Komplexbildung mit den Metallionen wurden ermittelt.

     

Vanadium(III) chloride as an effective catalyst for the Pechmann reaction

Good yields of substituted coumarins were obtained by a synthetic method involving the Pechmann reaction using vanadium(III)chloride (VCl₃) reagent to effect this condensation under solvent-free conditions. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 197–200, February, 2006.     

Fe(III) chloride catalyzed conversion of epoxides to acetonides

A mild and efficient method for the preparation of acetonides from epoxides catalyzed by iron(III) chlorides has been developed.     

Intradiffusion and viscosity measurements in acidified iron(III) chloride solutions at 25°C

Intradiffusion of species in acidified (using eithe hydrochloric or perchloric acid) iron(III) chloride solutions has been studied using labeled iron(III), chloride and water. Comparison with data for iron(III) perchlorate has enabled the influence of complexed species upon the diffusion to be ascertained. The chloro-iron species formed have larger diffusion coefficients than the free iron(III) ion as would be expected from their lower net charge. Simple diffusion models have been employed to enable estimates of the diffusion of the complexed species and of the free chloride diffusion coefficients to be obtained. These are discussed in relation to literature data for similar systems. In addition esitmates of the effective hydration of the iron(III) species in solutions have been obtained from the diffusion data. These are discussed in relation to two other trivalent metal salt systems, chromium chloride and lanthanum chloride; the overall hydration of the three cations is virtually identical.     

Oxidation of ketones by cerium(IV) in presence of iridium(III) chloride

Kinetic data, in iridium(III) chloride catalyzed oxidation of ethyl methyl ketone (EMK) and methyl propyl ketone (MPK) by cerium(IV) perchlorate in aqueous perchloric acid medium, suggest the formation of complex C₁ between cerium(IV) and organic substrate in the first equilibrium step, which in turn gives rise to another complex C₂ with the catalyst. This second complex in the rate-determining step gives rise to the intermediate products. Interestingly IrCl_3, which is considered to be a sluggish catalyst in alkaline media, was found to surpass the catalytic efficiency of even osmium and ruthenium in acidic media. Rate decreases in the beginning at low acid concentrations, but after reaching to a minimum it becomes directly proportional to acid concentrations. Probably on increasing the acid concentrations hydrolyzed species of ceric perchlorate gradually converts into the un-hydrolyzed species, which then accelerates the rate at higher [H⁺], resulting in the observed peculiar effect of hydrogen ions on the rate. Initial concentrations of cerium(IV) and acid determine the extent of reduction of cerium(IV) by water. Order of the reaction shows direct proportionality with respect to the oxidant and ketones at their low concentrations, but tends to become zeroth order at their higher concentrations. Rate of the reaction shows direct proportionality with respect to [IrCl₃] while change in ionic strength of the medium does not affect the reaction velocity. Parameters such as the energy of activation, free energy of activation and entropy data suggest that methyl propyl ketone forms the activated complex more easily compared to ethyl methyl ketone.     

Complexes of oxamic acid with Au(III) and Rh(III)

The preparation and some properties of the deprotonated complexes of oxamic acid with Au(III) and Rh(III) are reported. On the basis of analytical results, conductometric measurements, magnetic moments and spectral data (IR and UV-visible), a square planar structure is proposed for K[AuL(OH)₂] and octahedral for K₃[RhL ₃] 3H₂O (whereLH₂=oxamic acid).L ^2– acts as a bidentate, non-bridging ligand.

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Komplexe der Oxamidsäure mit Au(III) und Rh(III)

Zusammenfassung Es wird über die Darstellung und einige Eigenschaften von deprotonierten Komplexen der Oxamidsäure mit Au(III) und Rh(III) berichtet. Auf der Grundlage von analytischen Ergebnissen, Leitfähigkeitsmessungen, magnetischen Momenten und IR- und UV(vis)-spektroskopischen Daten wird für K[AuL(OH)₂] eine quadratisch planare und für K₃[RhL ₃] 3 H₂O eine oktaedrische Struktur vorgeschlagen (LH₂=Oxamidsäure).L ^2– reagiert als zweizähniger, nicht überbrückender Ligand.

     

Thermal Behaviour of Some Iron(III) Complexes with Active Therapeutically Biguanides

Two iron(III) complexes with therapeutically active biguanides - N',N'-anhydrobis-(beta-oxyethyl) biguanide (HMBig), and N',N'-dimethylbiguanide (HMetf), respectively - [Fe(HMBig)₃]Cl₃·9H₂O (I) and [Fe(HMBig)(HMetf)]Cl₃·6H₂O (II) - were synthesized and characterized through elemental analysis, electrical conductivity, IR and UV/VIS spectroscopy, measurements in magnetic field and non-isothermal analysis. In studied complexes the biguanide derivatives act as bidentate ligands through nitrogen atoms of the iminic groups. Their magnetic moments correspond to iron(III) in the spin quartet ground state. The thermal analysis evidenced an endotherm release of crystallization and coordinated water molecules. The degradation of the ligand molecules is a complex one, several processes being overlapped. The presence of biguanidic ligand increase the thermal stability of the coordination compound. The final product of both thermal decompositions is a-Fe₂O₃. This revised version was published online in July 2006 with corrections to the Cover Date.     

氨基羧酸铁(III)配合物催化分解过氧化氢

用碘量法研究了[Fe（EDTA],[FeⅢ(DCTA)],[FeⅢ(EGTA)]催化分解H2O2反应，提出了反应动力学方程为-d[H2O2]/dt=k[FE(Ⅲ)][H2O2][H ]^-1，认为氨基羧酸铁（Ⅲ）配合物催化分解H2O2反应为键式自由基反应，反应中间体包括过氧铁（Ⅲ）配合物，氨基羧酸铁（Ⅱ）和HO-，HO2-自由基。     

Thermal dehydrochlorination of poly(vinylidene chloride)

The kinetics of the early stages of thermal degradation below 1% dehydrochlorination of emulsion-polymerized poly(vinylidene chloride) (PVDC) is studied by the variation of the pH value of potassium hydroxide aqueous solution between 160 and 190°C in the presence of air and other gas streams. The results turned out that the thermal degradation of PVDC can be divided into three stages, which correspond to an induction period, a period with conversion below 0.1% dehydrochlorination, and that with conversion ranging from 0.1 to 1%. For the induction stage, the induction time depends upon the types of environment gas and degradation temperature. Both of the second and the third stages are zero-order reactions, which also result in the discoloration and crosslinking of the neat polymer. The average apparent activational energy of the zero-order degradation reaction was about 21 kcal/mol, which is independent of the types of environment gas. The whole degrading kinetics data can be well explained by the mechanism of a free-radical-induced dehydrochlorination. The viscosity of the degraded sample increases rapidly with degradation and becomes insoluble in regular solvents. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2035–2044, 1999     

Thermal Analysis of Fe(III) Complexes with Salicylaldehyde Semi-, Thiosemi- and S-methylisothiosemi-carbazones

The paper describes the results of differential thermal analysis of the octahedral Fe(III) complexes of the general formula [Fe(HLⁿ)₂]Cl and Fe(HL³)L³, as well as of the corresponding ligands H₂Lⁿ (H₂Lⁿ — tridentate salicylaldehyde semi thiosemi- and S-methylisothiosemi-carabazones with n=1, 2 and 3 respectively). The decomposition of the complexes involving sulphur-containing ligands (H₂L² and H₂L³) starts with sulphur elimination. In case of the complexes [Fe(HL²)]Cl and [Fe(HL³)]Cl sulphur evolves independently, whereas with Fe(HL³)L³ it is eliminated within the SCH₃ group. In the former case, sulphur elimination takes place at the same temperature for both complexes. The change in the coordination mode, being a consequence of the replacement of O by S, has no essential effect on thermal stability of the coordination polyhedron. The complexes involving ONN coordination, realized with the H₂L³ ligand, exhibit a comparatively highest thermal stability of the coordination polyhedron.This revised version was published online in November 2005 with corrections to the Cover Date.     

Surface Properties of Poly(vinyl alcohol) with Iron(III)chloride Before and After UV-Irradiation

Summary: Surface properties of poly(vinyl alcohol) (PVA) with low content of FeCl₃ (1, 5 wt.%) were studied by measurements of contact angles and atomic force microscopy. The results of contact angles and the surface free energy calculations revealed that the hydrophilicity of the surface of PVA films depended on the content of iron (III) chloride in these polymeric films. Introduced salt also affected photochemical reactions in poly(vinyl alcohol). Photooxidation of PVA was more effective in the presence of FeCl₃ because of formation of reactive chlorine atoms, which were capable of initiating new reactions. Also the morphology and roughness parameters of PVA film changed when iron (III) chloride was added.