Kinetic analysis of thermogravimetric data. XVIII. Thermal decomposition of some [Co(AMINE)2 (NCS)2] type complexes

[Co(p-toluidine)₂(NCS)₂] (I), [Co(m-toluidine)₂(NCS)₂] (II) and [Co(aniline)₂(NCS)₂] (III) have been synthesized. Kinetic parameters n, E and Z (apparent reaction order, activation energy and pre-exponential factor) have been derived from the TG curves recorded under 12 different working conditions. The influence of the sample weight (m_o) and of the heating rate (q) upon the kinetic parameters as well as upon the decomposition temperature and the amount of amine liberated in the first decomposition stage are discussed. Mean values of the activation energy and of the decomposition temperature are discussed in terms of the Co—amine bond strength and molecular structure based on IR evidence.     

Reactivity of cobaloxime bound to polystyrene chain by carbon–cobalt σ bond

The (alkyl)-bis(dimethylglyoximato)pyridinecobalt attached to polychloromethylstyrene by a cobalt–carbon bond was prepared by the reaction of Co(II)(DH)₂Py with polychloromethylstyrene in benzene. The fraction of p-vinylbenzyl·Co(DH)₂Py introduced to the polymer was 8.1 and 2.1 mole %. The photodecomposition of the polymer-bonded cobaloxime was investigated by following the change of the visible spectrum. The rate constant k_dec of the polymer-bonded cobaloxime was 1.1 × 10^?2 sec^?1 in benzene; it is one-fourth of that of its monomeric analog, benzyl·Co(DH)₂Py. The k_dec values of the cobaloximes were also measured in benzene–dimethyl sulfoxide mixed solvents, and the polymer effects were discussed. The dependence of the photodecomposition on energy of the irradiation light was investigated, and it was found that the absorption band near 470 nm is important for the photodecomposition of the cobalt–carbon bond. Spectroscopic measurements of the ligand exchange reaction of polymer-bonded cobaloxime with pyridine in dimethyl sulfoxide gave a larger equilibrium constant (1.2 × 10⁴ liter/mole) than that of benzyl·Co(DH)₂Py (9.4 × 10² liter/mole). The kinetic data of the ligand exchange reaction indicated that the larger equilibrium constant for the polymeric system is due to the smaller rate constant of the reverse reaction. The thermodynamic parameters were also obtained.     

Synthesis,structure, CMC values,thermodynamics of micellization,steady-state photolysis and biological activities of hexadecylamine cobalt(III) dimethyl glyoximato complexes

Metallosurfactant complexes of the type trans- [Co(DH)₂(HA)X], where DH = Dimethyl glyoxime, HA = Hexadecyl amine and X = Cl⁻, Br⁻, I⁻, N₃ ⁻, NO₂ ⁻ or SCN⁻, were synthesized and characterized by physico-chemical and spectroscopic methods. In addition, the single crystal X-ray structure of the ionic complex trans-[Co(DH)₂(HA)₂][Co(DH)₂(I)₂)] is presented. The critical micelle concentration values of the complexes in ethanol were obtained by measuring the absorption at 290 nm. Specific conductivity data (at 303–313 K) served for the evaluation of the thermodynamics of micellization ) \left( {\Updelta G^{0}_{{{\text{m}}}}, \Updelta H^{0}_{{{\text{m}}}}, \Updelta S^{0}_{\text{m}} } \right) . Steady-state photolysis, cyclic voltammetry and biological activities of the complexes were studied. The compounds were tested for antimicrobial activity.     

Kinetik und Mechanismus der Substitutionsreaktionen von Komplexverbindungen. XLII Nichtelektrolyte des Typs[Co(DH)2(NH3)X] und ihre Aquotisierungskinetik

Kinetics and Mechanism of the Substitution Reactions of Complexes. XLII. Nonelectrolytes of the Type [Co(DH)₂(NH₃)X] and their Aquation Kinetics A new synthesis of the complexes [Co(DH)₂(NH₃)Br] and [Co(DH)₂(NH₃)I] is given. IR spectra and structure of these nonelectrolytes are discussed. Aquation kinetics of these compounds is studied in acid solutions. In solutions of high acidity only the slow exchange of the halogen for water molecules occurs. In less acid and in neutral solutions aquation becomes much faster and also ammonia is substituted. Rate constants, activation enthalpy, and entropy values are compared to kinetic parameters of the aquation of other [Co(DH)₂XY] type complexes, where X stands for Cl, Br, I, and Y for Cl, Br, I, H₂O, and NH₃. Results are discussed in therms of protolytic equilibria and of the corresponding electronic effects.     

Thermal deamination of some complexes of the type [CO(Diox·H)2 (Amine)2]X

The thermal deamination of [Co(diox·H)₂(amine)₂]X type complexes were studied in dynamic temperature conditions (diox·H₂ stands for 1,2-cycloheptanedione dioxime (heptoxime, heptox·H₂) and 1,2-cyclo-octanedione dioxime (octoxime, octox·H₂), amine for aniline and pyridine,X for Br, I and NCS). Kinetic parametersn, E and logZ have been derived for some derivatives by means of two computerized integral methods. The influence of the sample weight, heating rate and chemical constitution upon the kinetic parameters, as well as the kinetic compensation effect are discussed.

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Thermische Desaminierung einiger Komplexe des Typs [Co(Diox·H) ₂ (Amin₂]X. Über -Dioximinkomplexe der Übergangsmetalle, LXIV.

Zusammenfassung Die thermische Desaminierung einiger Komplexe des Typs [Co (Diox·H)₂(Amin)₂]X wurde bei dynamischen Temperaturbedingungen untersucht [Diox·H₂ bedeutet 1,2-Cycloheptandiondioxim, (Heptoxim, Heptox·H₂) und 1,2-Cyclooctandiondioxim (Octoxim, Octox·H₂), Amin bedeutet Anilin und Pyridin,X bedeutet Br, I, bzw. NCS]. Die kinetische Parametern, E und logZ wurden mit Hilfe von zwei computergeeigneten Integralmethoden bestimmt. Der Einfluß des Gewichtes der Proben, der Heizungsgeschwindigkeit und der chemischen Zusammensetzung auf die kinetischen Parameter, bzw. der kinetische Kompensationseffekt werden diskutiert.

     

Kinetic Analysis of Thermogravimetric Data XXXII. DSC Study of Some [Co(Diox·H)2(amine)2]X and H[Co(Diox·H)2(N3)2] Type Complexes with Alicyclic α-dioximes

14 mixed Co(III) dioximine chelates of the types [Co(Diox·H)₂(amine)₂]X (X = Br, I, NO₃, ClO₄) and H[Co(Diox·H)₂(N₃)₂], respectively (Diox·H₂-1,2-cyclohexane dione dioxime (nyoxime), 1,2-cycloheptane dione dioxime (heptoxime) 1,2-cyclooctane dione dioxime (octoxime) were obtained and their thermal decompositions were studied in an argon atmosphere. After the dehydration of the crystallohydrates, both types of complexes exhibit 3 decomposition stages. For the [Co(Diox·H)₂(amine)₂]X type complexes (X = Br, I) the first endothermal stage is the substitution of an amine molecule for the external sphere anion and this process is followed by two exothermal decomposition stages. With H[Co(Diox·H)₂(N₃)₂] type complexes the first and third processes are relatively slow, but the second process is very fast, corresponding to a vertical portion of the TG curves. From the TG curves kinetic parameters were derived for 11 processes and the validity of a non-linear compensation law was observed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Coordination chemistry of some new Cu(II), Ni(II) and Co(II) macroacyclic (N2O4) Schiff base complexes: X-ray crystal structure of Cu(II) complex

Six new Cu(II), Ni(II) and Co(II) macroacyclic Schiff base complexes [M^II(H₂L)](ClO₄)₂ (L = L¹ and L²) (I–VI) were prepared by the reaction of two new N₂O₄ Schiff base ligands in equemolar ratios. The ligands H₂L¹ and H₂L² were synthesized by reaction of 2-[2-(2-formyl phenoxy)ethoxy]benzaldehyde (A¹) and/or 2-[2-(3-formylphenoxy)propoxy]benzaldehyde (A²) and ethanol amine and characterized with IR and ¹H, ¹³C NMR spectroscopy. All complexes were characterized by microanalysis, IR and mass spectrometry, whereas complex I was also characterized by single crystal X-ray (CIF file CCDC no. 1020055). The X-ray structure of complex I revealed that all nitrogen and oxygen atoms of ligand (N₂O₄) have coordinated to the metal ion. However, Cu²⁺ ion is in six coordination environment that can bedescribed as a distorted octahedral geometry.     

Trans-bis(dimethylglyoximato) cobalt(III) complexes containing imidazole and thiocyanate as axial ligands

Imidazole(Im), benzimidazole(BzIm), morpholine (Morph) and their derivatives react with Co(CNS)₂ and dimethylglyoxime(DH₂) in ethanolic medium in presence of air to form a number of new cobalt(III) complexes of the type trans-[Co(DH)₂(L)(SCN)], which are characterised on the basis of electronic and IR spectra, NMR (¹H and ¹³C) and mass spectra as well as thermogravimetric (TG-DTA) and conductance measurements. The thiocyanate groups are S-bonded. The NMR observations suggest that in solution these compounds exist as mixtures of the neutral species [Co(DH)₂(L)(SCN)] and the salt [Co(DH)₂(SCN)₂]^? [Co(DH)₂(L)₂]⁺. The mass spectra does not show the molecular ion peak of the complex. The TG-DTA measurements show that the thermolysis of these complexes proceeds through polymeric intermediates giving CO₃O₄ as the end product.     

Kinetic Analyis of TG Data XXXV. Spectroscopic and thermal studies of some cobalt(III) chelates with ethylenediamine

A number of 30 [Co(en)₃ ]Y₃ , [Co(en)₂ X₂ ]Y and [Co(en)₂ X(amine)]Y₂ type complexes (X =Cl, Br; Y =Cl, Br, I, NCO, NCS, NO₃ , ClO₄ , etc.; amine =aromatic and alkylamines) were obtained from trans-[Co(en)₂ Cl₂ ]Cl by double decomposition and by substitution reactions, respectively. The structure of the complexes was proved by means of far and middle FTIR spectra. The thermal decomposition was studied by TG, DTA and DSC measurements. Mass spectra were also recorded. In the case of [Co(en)₃ ]Y₃ complexes the nitrate, perchlorate and dimesoperiodates decompose suddenly, frequently explosion like. The halides and thiocyanates seem to substitute an ethylenediamine ligand, yielding a rather unstable intermediate. The pyrolysis of [Co(en)₂ X₂ ]Y type derivatives yields no relatively stable intermediates, but the decomposition temperatures may be correlated with the nature of Y and with the cis or trans configuration of the compound. With the [Co(en)₂ X(amine)]Y₂ type complexes one observes the formation of [Co(en)₂ XY]Y as intermediate product. From the TG curves kinetic parameters were derived for some dehydration and deamination processes, by using the nomogram method. The validity of a non-linear kinetic compensation law was observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Der Cyano-nitro-bis-biacetyldioximato-kobalt(III)-Komplex und seine Aquatisierungskinetik in saurem Medium

The [Co(BH)₂(CN)(NO₂)]^? complex (BH₂ = biacetyldioxime) has been obtained by means of an anatation reaction from the [Co(BH)₂(NO₂)(H₂O)] nonelectrolyte with KCN in aqueous solution. The free acid H[Co(BH)₂(CN)(NO₂)]·4 H₂O and 12 derivatives were obtained by double decomposition reactions. The thermal decomposition of some of these compounds was thermogravimetrically studied. Kinetics of the aquotization of the [Co(BH)₂(CN)(NO₂)]^? was investigated in acid solution by following the change of the concentration of the free NO₂ ^?-ions by means of a diazotation reaction. The kinetic parameters of the reaction are given.     

Synthesis, X-ray structure, and spectroscopic investigation of new Co(II)/Cd(II) complexes formed via the reaction of 1-hydroxymethyl-3,5-dimethylpyrazole and Co0, CdCl2, NH4I

The novel complex [Co(L)Cl]₂[CdI₄] obtained in situ from the redox system (Co⁰, CdCl₂, NH₄I, 1-hydroxymethyl-3,5-dimethylpyrazole) was characterized by X-ray diffraction IR, UV–VIS as well as magnetic and thermal investigations. The ligand, tris(1-(3,5-dimethylpyrazolylmethyl)amine (L) was synthesized in situ as a product of condensation 1-hydroxymethyl-3,5-dimethylpyrazole and ammonia molecule formed during redox process. The crystal structure of 1 includes in the unit cell two chemically identical but symmetry-independent cations: [Co(1)(L)Cl]⁺ and [Co(2)(L)Cl]⁺. Each of the [Co(L)Cl]⁺ complex ions has C₃ point group symmetry, but the point group symmetry of the trigonal bipyramidal coordination spheres of [CoN₃N′Cl] and tetrahedral sphere of [CdI₄] has C_3v point group symmetry.     

Thermoanalytical study of linkage isomerism in coordination compounds

The non-isothermal differential scanning calorimetry (DSC) experiments revealed that linkage isomerization of both pure trans-[Co(en)₂(ONO)₂]PF₆ (dinitrito isomer) and trans-[Co(en)₂(NO₂)₂]PF₆ (dinitro isomer) occurs in the solid state at elevated temperatures. The process was found to be exothermic for the dinitrito isomer and endothermic for dinitro isomer. The pure isomers could be considered to be in metastable states at ambient temperatures which would be converted to an equilibrium mixture of both isomers (stable state) upon heating. Since the isomerization of both isomers may be described as a two stages process, the corresponding DSC peaks have been resolved into two peaks by means of nonlinear curve fitting tools of PeakFit^® software. The resolution of the peaks helped us to determine enthalpy changes of stepwise isomerization of both isomers. A first-order initial rate and Kissinger methods have been employed to estimate kinetic parameters of the stepwise isomerization reactions. The Kissinger method provided more reliable kinetic results. The high activation energy and positive entropy changes of isomerization of both isomers are considered as indication of a dissociative mechanism in solid state.     

Synthesis and crystal structure of cobalt(III) α-dioximates with pyrazine

A series of new coordination compounds of cobalt(III) trans-dioximates with pyrazine [CoCl(DH)₂Pz] · H₂O (I), [CoBr(DH)₂Pz] · H₂O (II), [Co(DH)₂Pz₂]NO₃ · H₂O (III), [Co(DH)₂Pz₂][BF₄] (IV), [Co(MgH)₂Pz₂][BF₄] (V), and [Co(NioxH)₂Pz₂][BF₄] (VI), where DH, MgH, and NioxH are dimethylglyoxime, methylglyoxime, and 1,2-cyclohexanedionedioxime monoanions, respectively, Pz is a pyrazine molecule were synthesized. The structures of compounds I, II, and VI were determined by X-ray diffraction. The Co(III) environment in these compounds is octahedral and the pseudomacrocyclic (DioxH⁻)₂ fragment occurs in the equatorial plane. This fragment is stabilized by O-H…O hydrogen bonds. The neutral Pz ligand is monodentate in all three compounds.     

Structure of aniline-containing Co(III) <Emphasis Type="Italic">trans</Emphasis>-dioximates with the [ZrF<Subscript>6</Subscript>]<Superscript>2−</Superscript> anion

Two new coordination compounds, trans-octahedral aniline-containing Co(III) dioximates [Co(DH)₂(Anil)₂]₂[ZrF₆]·2H₂O (I) and [Co(NioxH)₂(Anil)₂]₂[ZrF₆]·3H₂O (II), where DH^? is the dimethylglyoxime monoanion, and NioxH^? is the 1,2-cyclohexanedionedioxime monoanion, were synthesized, and their crystal structures were studied by XRD. In I, two centrosymmetric, crystallographically independent [Co(DH)₂(Anil)₂]⁺ complex cations (A and B) are linked by a system of hydrogen bonds, the [ZrF₆]^2? centrosymmetric anion, and the crystallization water molecules into a three-dimensional framework. The coordination polyhedron of the Co³⁺ atom in I and II is a slightly distorted N₆ octahedron formed by four nitrogen atoms of the two dioxime residues and two amine nitrogen atoms of the aniline fragment. The deviation of the cobalt atom from the plane of the metallocycle in II is up to 0.012 Å. The [ZrF₆]^2? outer-spheric anions and crystallization water molecules dominate in the crystal structures.     

Imidazole cobaloximes containing nitro or nitrate

Summary A series of yellow or brown stable cobaloxime complexes containing imidazole and nitro or nitrate groups of general formula [Co(DH)₂(NO₂)(L)] or [Co(DH)₂(H₂O)(L)](NO₃). (DH₂=dimethylglyoxime, imidazole, morpholine or their derivatives) has been synthesized and characterized by elemental analyses, electronic and i.r. spectra, conductance measurements.¹H n.m.r. spectra and thermogravimetric analysis. The ambidentate nitro-groups are unambiguously N-bonded (-NO₂) and the nitrate groups are ionic, as is clear from the i.r. spectra.     

Reduction of carbon dioxide by tris(2,2′-bipyridine)cobalt(I)

Preliminary stoichiometric and kinetic results bearing on the mechanism of the reduction of HCO₃⁻ to CO by tris(2,2′-bipyridine)cobalt(I) in aqueous media are reported. The results indicate that CO (not formate) is the dominant carbon product and that it is scavenged by Co(bpy)₃⁺ to give insoluble [Co(bpy)(CO)₂]₂. At pH ∼ 9, bicarbonate reduction occurs in competition with H₂O reduction. Both processes are inhibited by bpy and promoted by H⁺, suggesting the common intermediate Co(bpy)₂(H₂O)H²⁺. The bicarbonate reaction itself branches to give H₂ and CO in ∼ 3:1 ratio.     

Effect of amines on the ceric ion-initiated polymerization of vinyl monomers. II. Polymerization of acrylonitrile by ceric ion in presence of various substituted amines

The effect of various substituted amines on the polymerization of acrylonitrile initiated by ceric ammonium sulfate has been studied in aqueous solution at 30°C. It was found that the secondary and tertiary amines considerably increased the rate of polymerization, whereas the primary amines seemed to have no effect at all. From the kinetic studies it was found that the overall polymerization rate R_p is independent of ceric ion concentration and can be expressed by the equation: R_p = k₁ [amine] [monomer] + k₂[monomer]², where k₁ and k₂ are constants (involving different rate constants). The accelerating effect of the amines was attributed to a redox reaction between the ceric ion and the amine involving a single electron transfer, the relative activity of the different amines being thus dependent on the relative electron-donating tendency of the substituents present in the amine. The mechanism of the polymerization is discussed on the basis of these results, and various kinetic constants are evaluated.     

A study of some amine,pyridine and 3,5-lutidine complexes of trimethylplatinum(IV)

The reactions of trimethylplatinum(IV) compounds with a number of amines have been examined. With ammonia and methylamine, tris-and mono(amine)species have been obtained, but no bis(amine)species apart from [pt(CH₃)₃(NH₃)₂I]. With ethylamine the bis(amine)species is formed with excess ligand. The ¹H NMR spectra of [Pt(CH₃)₃LI]₂ (L=pyridine, 3,5-lutidine) exhibit evidence for two isomers in solution and an equilibrium of these compounds with [Pt(CH₃)₃L₂I] and [Pt(CH₃)₃I]₄.     

Cobalt(III) dimethylglyoximates containing selenourea and an unusual diselenourea ligand: Synthesis and structures

The complexes [Co(DH)₂(Seu) _y (Se-Seu) _z ]₂X · mSolv (DH is the dimethylglyoxime monoanion, Seu is selenourea, and X is [TiF₆]²⁻, [ZrF₆]²⁻) were obtained from the system CoX · 6H₂O-DH₂-Seu in DMF-MeOH or MeOH-H₂O and examined by UV, IR, and NMR spectroscopy and X-ray diffraction. Unexpectedly, the ligand Se-Seu (the oxidized form of selenourea) was detected on the axial coordinate, partially replacing selenourea. The complexes were formulated as [Co(DH)₂(Seu)_1.75(Se-Seu)_0.25]₂[TiF₆] · H₂O (I) and [Co(DH)₂(Seu)(Se-Seu)]₂[ZrF₆] · 3H₂O (II). The complex cations in I and II have trans-octahedral structures. Their crystal structures are made up of the complex Co³⁺ cations and the outer-sphere MF₆²⁻ anions (M = Ti(IV) (I) and Zr(IV) (II)) held together by electrostatic interactions and hydrogen bonds; water of crystallization is also involved in hydrogen bonding.     

Cobalt(II) complexes of creatinine

Summary Cobalt(II) complexes of creatinine [Co(creat)₂X₂] (X = Cl, Br, I or NCS) and [Co(creat)₂X₂(H₂O)₂] (X = HCO₂, HOCH₂CO₂ or CNCH₂CO₂) have been prepared. Their i.r. spectra show an increase in (NH) of the cyclic secondary amine group, compared to free ligand (3300 cm^–1), indicating that cyclic nitrogen is involved in coordination. The thiocyanate group coordinates through nitrogen and carboxylates coordinate as univalent unidentate ligands. The electronic spectra and magnetic moments suggest a d⁷ configuration for cobalt: a tetrahedral geometry (4.4 B.M.) for halide and thiocyanate complexes, and an octahedral geometry (5.0 B.M.) for the carboxylate complexes. On heating, the ligand moiety is lost and the respective cobalt halide or cobalt carboxylate is formed, which is converted finally into Co₃O₄. There is a correlation between the high intensity electronic transitions and the polarographic half-wave potentials.