Thermal decomposition kinetics of Schiff base complexes of copper(II) and palladium(II)

Thermogravimetric (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) curves of CuL₂ and Pd(LH)₂Cl₂ (LH=salicylidene-2-aminofluorene and 2-hydroxy-1-naphthalidene-2-aminofluorene) in air are studied. Mass loss considerations at the main decomposition stages indicate conversion of the complex to oxides. Mathematical analysis of TG data shows that first order kinetics are applicable in all cases. Kinetic parameters (energy and entropy of activation and preexponential factor) are reported.     

Platinum(II) and palladium(II) complexes with substituted pyrimidines

Summary Platinum(II) and Palladium(II) complexes with 2-mercaptopyrimidine, 2-thiocytosine (4-aminopyrimidine 2-thione), and isocytosine (2-amino-4-hydroxy pyrimidine) were prepared and characterised by elemental analysis, conductivity data, i.r.,¹H n.m.r. and¹³C n.M.r. spectral studies. 2-Mercaptopyrimidine and 2-thiocytosine are coordinated to the metal ion through N(3) and C₂S, thus forming a four-membered chelate ring. Isocytosine acts as a monodentate ligand and coordinates to the metal ion through N(1). All the complexes are non-electrolytes.     

Thermal decomposition kinetics of thiophene-2-carboxaldehyde thiosemicarbazone complexes of nickel(II) and palladium(II)

The thermal analysis of Ni(II) and Pd(II) complexes with thiophene-2-carboxaldehyde thiosemicarbazone have been studied using TG technique. Their decompositions are subjected to critical evaluation using the equations of Coats-Redfern, Horowitz-Metzger and modified Horowitz-Metzger and the kinetic parameters (non-isothermal method) have been evaluated for each step of decomposition by the method of weighted least-squares.     

Thermal decomposition kinetics of palladium(II) 1‐allylimidazole complexes

Thermal dehydration and decomposition processes of a Pd(II) coordination compound, [PdL₄]Cl₂·3H₂O ( 1 ), (where L is 1‐allylimidazole) were studied by simultaneous TG/DSC techniques under constant heating rates condition. The released gas products were analyzed by online coupling a FTIR spectrometer to the TG equipment. The so obtained evolved gas analysis confirmed that only two ligand molecules were released and that a new 1‐allylimidazole Pd(II) complex, trans‐[PdL₂Cl₂] ( 2a ), was obtained. The same coordination compound was also prepared by heating 1 at 413.15 K in air atmosphere until a constant weight was reached 2b . Thermal decomposition mechanisms for the 2a and 2b complexes examined were proposed according to the three mass loss steps derived by TG data. Based on the model‐free isoconversional method described by Flynn–Wall–Ozawa (FWO), the dependencies of activation energy on the degree of conversion were determined. A model‐free “single point” method was also applied using the Kissinger equation, and derived results were compared to those of the former method. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 667–674, 2005     

Thermal and spectral studies of palladium(II) complexes

Palladium(II) complexes of type [Pd(L)Cl₂] [where L=2-aminopyridine-N-thiohydrazide (L¹), (2-aminopyridine-N-thio)-1,3-propanediamine (L²), benzaldehyde 2-aminopyridine-N-thiohydrazone (L³) and salicylaldehyde-2-aminopyridine-N-thiohydrazone (L⁴)] have been synthesized. The thiohydrazide, thiodiamine and thiohydrazones can exist as thione-thiol tautomer and coordinate as a bidentate N-S ligand. The ligands found to act in bidentate fashion. The complexes have been characterized by elemental analysis, IR, mass, electronic, ¹H NMR spectroscopic studies, and TG/DTA study. Antifungal studies of some complexes were also carried out. Various kinetic and thermodynamic parameters like order of reaction (n), activation energy (E _a), apparent activation entropy (S ^# ) and heat of reaction (ΔH) have also been carried out for one complex.     

Thermal decomposition of some N-oxide complexes of cobalt(II), nickel(II) and copper(II) carboxylates

Thermal decomposition of mono pyridine N-oxide complexe; of cobalt(II), nickel(II) and copper(II) propionates and mono quinoline N-oxide complex of copper(II) ben zoate has been studied by TG and DTA techniques. These dimeric complexes are stable upto 350–380 K and decompose in two stages: (i) successive elimination of the two ligand molecules (mostly endothermic); and (ii) decomposition of the resulting anhydrous metal(II) carboxylates by an exothermic multistep process in air.

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Zusammenfassung Die thermische Zersetzung der Monopyridin N-oxidkomplexe der Kobalt(II)-, Nickel(II) und Kupfer(II)-propionate sowie des Monochinolin N-oxidkomplexes von Kupfer(II)-benzoat wurden durch TG und DTA-Methoden untersucht. Diese dimeren Komplexe sind bis zu 350–380 K stabil und werden in zwei Stufen zersetzt: (i) sukzessive Eliminierung der zwei Ligandmoleküle (hauptsÄchlich endotherm); und (ii) Zersetzung der entstehenden wasserfreien Metall(II)carboxylate durch einen mehrstufigen exothermen Vorgang in Luft.

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Résumé On a étudié, par TG et ATD, la décomposition thermique des propionates des complexes mono-pyridine N-oxyde de cobalt(II), de nickel(II) et de cuivre(II) ainsi que du benzoate mono-quinoline N-oxyde de cuivre(II). Ces complexes dimères sont stables jusqu'à 350–380 K et se décomposent en deux étapes: (i) élimination successive des deux moléculesligands (la plupart du temps endothermique); et (ii) décomposition des carboxylates anhydres des métaux(II) formés par un processus en plusieurs étapes dans de l'air.

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-N- (II), (II) (II), -N- (II). 350–380 : (1) (2) .

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The authors are thankful to Dr. R. K. Dewan, Head of the Chemistry Department, University of Jammu, Jammu for providing necessary facilities in the department. The authors are also indebted to Dr. O. P. Vig, Head of the Chemistry Department, Panjab University, Chandigarh for assistance provided. One of the authors (R. K.) is grateful to University Grants Commission, New Delhi for the award of Junior Research Fellowship.     

Thermal decomposition of oxovanadium(IV) complexes with substituted pyridines

The kinetics of decomposition of solid complexes of bis(dibenzoylmethanato) oxovanadium(IV) with pyridine and several methyl, dimethyl and aminopyridines has been studied using differential scanning calorimetry. Activation energies have been determined and, in general show an increase with increasing basicity of the ligands. A linear relationship exists between pK_b values of the bases and the temperatures for the decomposition, except for the complexes obtained with 4 aminopyridine and 4 methylpyridine. These complexes are less stable than expected from the basicity of the ligands. These observations are discussed in terms of the nature of the metalligand bond.     

Thermal decomposition study of cobalt(II)-mixed ligand complexes with aliphatic or aromatic dicarboxylic acids and imidazole

The thermal decomposition study of Co(II)–malate, tartarate and phthalate complexes with imidazole was monitored by TG, DTG and DTA analysis in static atmosphere of air. The complexes and their calcination products were characterized by IR spectroscopy. The decomposition course and steps were analyzed and the kinetic parameters of the non-isothermal decomposition were calculated. The results revealed that the decomposition processes of these complexes are the best described by a random nucleation mechanism. The stability order found for these complexes follows the trend tartarate>phthalate>malate in terms of the dicarboxylic acid ligands.     

Thermal properties of mercury(II) and palladium(II) purine and pyrimidine complexes

Six solid Pd(II) and Hg(II) complexes of some purines and pyrimidines have been prepared and characterized by elemental analyses, IR, UV–Vis spectra, magnetic measurements, and thermal analyses. The data suggest tetrahedral and square planar geometries for mercury and palladium complexes, respectively. The thermal behavior of the complexes has been studied applying TG, DTA, and DSC techniques, and the thermodynamic parameters and mechanisms of the decompositions were evaluated. The ?S* values of the decomposition steps of the metal complexes indicated that the activated fragments have more ordered structure than the undecomposed complexes, and/or the decomposition reactions are slow. The thermal processes proceeded in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing small molecules such as H₂O, HCl or C=O. The palladium adenine complex is ended with the metal as a final product. However, the thermal reactions of the other five palladium and mercury pyrimidines complexes are ended with metal bonded to O, N, or S of the pyrimidine ring.     

Thermal decomposition of some homobinuclear dihalide-bridged iron(III) complexes

Thermal studies by TG and DTG on some homobinuclear dihalide-bridged iron(III) complexes of the general type [Fe(S₂CNR₂)₂X]₂(}-X ₂) were carried out in air and nitrogen atmospheres. The apparent activation energies were determined by graphical methods and the TIN temperatures were calculated from the TG profiles. Finally, a possible mechanism of the decomposition is suggested on the basis of the pyrolysis and mass spectral data.

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Zusammenfassung Einige homobinukleare Eisen(III)-Komplexe mit Dihalidbrücken der allgemeinen Formel [Fe(S₂CNR₂)₂X]₂(–X₂) wurden mittels TG und DTG in Luft und Stickstoffatmosphäre untersucht. Die scheinbaren Aktivierungsenergien wurden nach graphischen Methoden aus den TG-Profilen bestimmt. Ein möglicher, auf pyrolytischen und massenspektrometrischen Daten basierender Zersetzungsmechanismus wird vorgeschlagen.

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[Fe(S₂CNR₂)₂X]₂ (-₂) . , . - .

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Thanks are due to Dr. G. Karagiannidis, Laboratory of Organic Chemical Technology, Aristotelian University, for technical assistance.     

Syntheses and characterisation of some triphenylcyanoborate complexes of rhodium(II) and palladium(II)

The triphenylcyanoborate (N-bonded) complexes {η⁵-(C₅Me₅)Rh(SS)-NCBPh₃} (SS? =^?S₂PMe₂,^?S₂PPh₂,^?S₂CNMe₂), {η⁶-(C₆H₆)Ru(S₂PPh₂)-NCBPh₃} and [Pd(S₂ CNEt₂)(PMe₂Ph)(NCBPh₃) have been synthesised and characterised by both spectroscopic and X-ray structural methods.     

Spectroscopic studies on some complexes of nickel(II) and palladium(II) with thiosemicarbazides

Summary The electronic absorption spectra of the complexes M(L)Cl₂ and M(L)₂Cl₂ [M=Ni^II or Pd^II; L=thiosemicarbazide (tsc), 1-phenylthiosemicarbazide (1-phtsc), or 4-phenylthiosemicarbazide (4-phtsc)] were investigated in a number of solvents. The complexes Ni(tsc)Cl₂, Ni(tsc)₂Cl₂, Ni(4-phtsc)Cl₂ and Ni(4-phtsc)₂Cl₂ exist in a distorted O_h geometry when dissolved in any of the solvents used. On the other hand, the complex Ni(1-phtsc)₂Cl₂, although weakly paramagnetic, proved to be planar. Theoretical and experimental results proved that the complex has neither O_h nor T_d geometry. Molecular orbital calculations were performed on some selected complex ions assuming a local point group symmetry of D_2h.     

Thermal decomposition of complexes of cadmium(II) and mercury(II) with triphenylphosphanes

A series of substituted triphenylphosphane complexes of the type CdL₂X₂ (L= triorthotolylphosphane or trimetatolylphosphane; X=Cl⁻, Br⁻ or I⁻) and HgL₂X₂ (L=triphenylphosphane or triorthotolylphosphane) was prepared fresh. The thermal decomposition was carried out in air with heating rate programmed at 10°C min⁻¹ and it revealed that the complexes with ortho derivative were less stable and the triphenylphosphane moiety leaves along with halogen in the first step. All the complexes were stable up to 210°C. However, the stability order of the tetrahedral complexes was X=Cl>Br. Values of n, E, lnA and ΔS ^# have been approximated and compared. Complexes having Br have higher E _a, lnA and ΔS ^# values than that having Cl.     

Ultraviolet spectrophotometric characterization of copper(II) complexes with imidazole N-methyl derivatives of L-histidine in aqueous solution

In this study we considered pi-methyl-L-histidine (pi-methis) and tau-methyl-L-histidine (tau-methis) as ligands for copper(II) ion, in order to clarify, by means of ultraviolet (UV) spectroscopy in aqueous solution (T = 25 degrees C, I = 0.1 M), some aspects of the co-ordination mode with respect to other ligands of a previous study in which copper(II) complexes of L-histidine, N-acetyl-L-histidine, histamine, L-histidine methyl ester or carnosine were investigated. Particularly, UV spectra (300-400 nm) were recorded on solutions at various pH values, containing each binary system Cu-L; afterwards, an UV absorption spectrum for single complexes was calculated, taking into account the chemical model previously assessed, in order to fulfil a correct spectrum-structure correlation. The problem related to the eventual superimposition of the CT shoulder (approximately 330 nm) to copper(II) of OH- and imidazole pyridine nitrogen groups were now solved by means of a comparison of the UV spectra of dimer species formed by both pi-methis or tau-methis. Finally, copper(II) complex formation with 2,2'-bipyridine was taken into account to compare the behaviour of pyridine (from 2,2'-bipyridine) and pyridine imidazole nitrogens (from pi-methis or tau-methis) with respect to the UV charge transfer process to copper(II) ion.     

Studies of thermal decomposition of palladium(II) complexes with olefin ligands

Thermal decomposition kinetics of ML₂ (M = Ni(II) and Co(II); L = 5-(2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)hydrazono)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione) complexes were investigated by thermogravimetric analysis (TGA). The first decomposition process of the NiL₂ and CoL₂ complexes occurs in the temperature range of 320–350 °C. Kinetics parameters corresponding to this step, such as activation energy, E_α, and apparent pre-exponential factor, ln A_aap, were calculated from the thermogravimetric data at the heating rates of 5, 10, 15 and 20 K min⁻¹ by differential (Friedman's equation) and integral (Flynn–Wall–Ozawa's equation) methods. The results show that the activation energy evidently depends on the extent of conversion. As far as their activation energy is concerned, NiL₂ complex shows a higher thermal stability than the CoL₂ complex.     

Synthesis and characterization of palladium(II) complexes of some tellurium heterocycles

Summary A series of square planar complexes of the type [PdX₂L₂] where X=Cl, Br, I; L=telluracyclopentane (tcp), telluracyclohexane (tch) or benzotelluracyclopentane (btp) have been synthesised. The complexes were characterised by far-i.r., n.m.r. and u.v.-vis. spectroscopy. The data implytrans-geometries except for the complex [PdCl₂(tch)₂] where a mixture ofcis- andtrans-isomers is obtained.     

Thermal decomposition of nickel(II) complexes under quasi-equilibrium conditions

The stoichiometry of thermal decomposition and the relationship between the thermal parameters (quasi-equilibrium decomposition temperaturesT _D and decomposition entalpies H _D) of NiL₄(NCS)₂ complexes (L=imidazole derivatives) were studied. It was found that changes in the experimental conditions strongly influence the decomposition stoichiometry. TheT _D and H _D can be ordered in the following sequence (according toL): imidazole<2-Me imidazole<2-Et imidazole相似文献   

Synthesis and evaluation of substituted pyrazoles palladium(II) complexes as ethylene polymerization catalysts

The substituted pyrazole palladium complexes, (3,5-^tBu₂pz)₂PdCl₂ (1) (3,5-Me₂pz)₂PdCl₂ (2), (3-Mepz)₂PdCl₂ (3) and (pz)₂PdCl₂ (4) (pzH=pyrazole), can be prepared from the reaction of (COD)PdCl₂ with the appropriate pyrazole. The chloromethyl derivative, (3,5-^tBu₂pz)₂PdCl(Me) (5), was prepared from (COD)PdClMe and ^tBu₂pzH. X-ray crystal structure determination of 1 and 5 established their structures in the solid state to be the trans-isomer. After activation of 1-4 and 5 with methylaluminoxane (MAO) the resulting palladium complexes were used as catalysts in ethylene polymerization, yielding linear high-density polyethylene (HDPE). The highest activity was observed for (3,5-^tBu₂pz)PdClMe.     

N-aminorhodamne complexes of palladium(II), palladium(IV) and platinum(II)

Summary TheN-aminorhodanine (L) complexes: PdLX, (X = Br or I), ML_1.5Cl₂ (M = Pd or Pt), PtL₂X₂ (X = Br, I or ClO₄), PdL₃(ClO₄)₂, PdL_1.5Cl₄ and PdL₃(ClO₄)₄ have been prepared and investigated. The ligand is bonded to the metal ion through the aminic nitrogen atom as monodentate or through this atom and the thiocarbonylic sulphur atom when it acts as chelating or bridging ligand. The carbonylic oxygen atom is never coordinated.