Ion Exchangers as catalysts I. Catalytic decomposition of hydrogen peroxide in presence of Dowex 50 W resin in the form of ethylamine-copper(II) complex ion in aqueous medium

Summary Dowex 50 W resin in the form of an ethylamine-Cu¹¹ complex ion was used as potentially active catalyst for the decomposition of H₂O₂ in aqueous medium. The stoichiometry of the amine-Cu¹¹ complex on the resin, determined experimentally, was found to have the total [Cu²⁺]: [ethylamine]=14 concentration ratio. The kinetics of the decomposition was studied and the calculated rate constant (per g of dry resin) was found to decrease with increase the degree of resin crosslinking. The active species, formed as an intermediate at the beginning of the reaction, had an inhibiting effect on the reaction rate. The brown peroxo-copper complex formed as a result of H₂O₂ decomposition, was found to contain the catalytic active species. The order of the reaction increased with decreasing initial H₂O₂ concentration, a sign of a step-wise mechanism. A quantitative treatment of the decomposition of H₂O₂ was provided in terms of activation parameters.     

Role of resin-manganese(II) complexes in hydrogen peroxide decomposition

The kinetics of hydrogen peroxide decomposition has been investigated in the presence of Wofatit KPS (4% DVB, 40–80 μm) resin in the form of mono (mea), di (dea), triethanolamine (tea), ethylenediamine (eda), and N,N′-diethylethylenediamine (deeda)- Mn(II) complexes. The rate constant k (per g dry resin) was evaluated over the temperature range 25–40°C. The reaction was first-order with respect to [H₂O₂]. The rate constant, k, with the three ethanolamines decreased in the following order mea > dea > tea which is the same order of basicity. Also, k value with deeda is lower than eda as a result of steric hindrance. The peroxo metal complex which formed at the beginning of the reaction, was found to contain the catalytic active species. The rate of reaction was proportional to [Mn-complex], [H₂O₂] and [H⁺]^?1. The activation parameters were calculated and a probable reaction mechanism is proposed. © 1994 John Wiley & Sons, Inc.     

Iron(II)-bis (salicyladimine) Schiff-base complexes catalyzed decomposition of hydrogen peroxide

The tetradentate Schiff-base ligands, N,N′-bis(salicylidene)-ethylenediamine (Salen), N,N′-bis(salicylidene) butylenediamine (Salbut), and N,N′-bis(salicylidene)-o–phenylenediamine, (sal-o-phen) are very strongly sorbed by cation exchange resin (Dowex-50W) with Fe²⁺ ions as a counter ion, forming stable complexes. The kinetics of the catalytic decomposition of H₂O₂ using these complexes was studied in ethanolic medium. The reaction was first-order with salen and sal-o-phen and second-order with salbut with respect to [H₂O₂]. The rate of the H₂O₂ decomposition increased either from salen to salbut or from salen to sal-o-phen. Also, the k (per g dry resin) values decreased with increasing both the particle size and the degree of resin cross-linkage. The active species formed at the beginning of the reaction, had an inhibiting effect on the reaction rate. The corresponding activation parameters were calculated from a least-squares fit of the temperature dependence of the rate constant. A reaction mechanism is proposed. © 1994 John Wiley & Sons, Inc.     

Kinetics of heterogeneous decomposition of hydrogen peroxide

The kinetics of the decomposition of hydrogen peroxide was studied in aqueous medium in the temperature range 25–40°C in the presence of Wofatit KPS-resin in the form of Cu(II)-ammine complex ions. The rate constant was deduced at various degrees of resin cross-linkage and different concentrations of hydrogen peroxide. The order of the decomposition reaction varied from first order to half order, i.e., the order of the reaction decreased with increasing the concentration of H₂O₂. The decomposition process was found to be a catalytic reaction which was controlled by the chemical reaction of H₂O₂ molecules with the active species inside the resin particles. The mechanism of the reaction can be summarized by the equation in which the subsequent reactions of the probable active complex are discussed.     

Kinetics of hydrogen peroxide decomposition with Fe(III) and Cr(III)-ethanolamines complexes sorbed on dowex-50W resin

The kinetics of the H₂O₂ decomposition in presence of Fe(III)- and Cr(III)-complexes of mono-, di-, and triethanolamine supported on Dowex-50W resin have been investigated. The decomposition process proceeded with first-order kinetics for the substrate concentration. The rate of reaction increased with increasing number of the coordinated ligands in the metal complex as well as with increasing ligand basicity. The decomposition reaction involved the formation of an intermediate active species, which converts into a peroxo-metal complex of brown, green, or gray color. A mechanism describing the decomposition process is proposed. © 1995 John Wiley & Sons, Inc.     

Oxidation of azo dye Orange II with hydrogen peroxide catalyzed by 5,10,15,20-tetrakis[4-(diethylmethylammonio)phenyl]porphyrinato-cobalt(II)tetraiodide in aqueous solution

The catalytic oxidation of the azo dye Orange II by hydrogen peroxide in aqueous solution has been investigated using 5,10,15,20-tetrakis-[4-(diethylmethylammonio)phenyl]porphyrinato-cobalt(II) tetra iodide 1as catalyst. The oxidation reaction was followed by recording the UV–vis spectra of the reaction mixture with time at λ_max = 485 nm. The factors that may influence the oxidation of Orange II, such as the effect of reaction temperature, concentration of catalyst, hydrogen peroxide and orange II have been studied. The results of total organic carbon analysis showed 52% of dye mineralization under mild reaction conditions. Residual organic compounds in the reaction mixture were identified by using Gas chromatography-mass spectrometry. The decolorization rate and mineralization of the dye has been found to increase with increase of catalyst concentration and reaction temperature. The rate of dye oxidation decreased with increasing the concentration of dye, H₂O₂ and at higher pH than 9. Radical scavenging measurement indicated that decolorization of Orange II by H₂O₂/cobalt (II) porphyrin complex 1 involved the formation of hydroxyl radicals as the active species.     

Synthesis and Thermal Decomposition of Cobalt(II) bis (Tartrato) Cobaltate(II) Trihydrate

The paper describes the synthesis and characterization of cobalt(II) bis (tartrato) cobaltate(II) trihydrate Co[Co[C₄O₆H₄)₂]·3H₂O. The complex was characterized on the basis of elemental analysis, infrared, electronic, e.s.r. spectra and X-ray powder diffraction studies. The thermal decomposition of the complex led to a mixture of Co₂O₃and Co₃O₄in air at about 400°C, whereas in nitrogen it was decomposed to a mixture of CoO and C at about 384°C. A tentative reaction mechanism is suggested for the thermal decomposition of the complex in air and nitrogen. This revised version was published online in July 2006 with corrections to the Cover Date.     

Heterogeneous kinetic studies of the hydrogen peroxide decomposition with some transition metal‐heterocyclic complexes

The heterocyclic compounds piperidine (Pip), piperazine (Pz), morpholine (Morph), and N‐methyl piperazine (N‐MPz) were used as ligands to form transition metal complexes with Ni(II), Cu(II), and Co(II) ions. These complexes were supported on Dowex‐50W resin so as to form new potential active catalysts for H₂O₂ decomposition in an aqueous medium. In all cases the reaction showed a first‐order kinetics with respect to H₂O₂ concentration, except with Co(II) complexes, the reaction showed a second‐order kinetics with 2% divinyl benzene (DVB) (50–100 mesh and 200–400 mesh). The rate constant k (per gram dry resin) was evaluated with a resin of cross‐linkage 2 and 8% DVB (50–100 mesh) and 2% DVB (200–400 mesh) over temperature range 25–40°C. With a given resin cross‐linkage, the rate constant has the following order: Ni(II) complexes < Co(II) complexes < Cu(II) complexes. With Pz ligand, k increased in the following sequence: Ni(II) complexes < Cu(II) complexes < Co(II) complexes. The reaction mechanisms of the first‐ and second‐order kinetics were discussed and the activation parameters were deduced. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 617–624, 2001     

Activity of metal chromate and phosphate supported on ion‐exchange resins toward hydrogen peroxide decomposition

The mixed resins, Dowex MR‐3 and MR‐12, in the H⁺/Cl⁻ form, and the cation resin, Dowex‐50W, in the H⁺ form, were used as a support for some metal chromate and phosphate salts. Similarly, anionic resin, Amberlite IRA‐400, in the Cl⁻ form, was used as a support for some metal chromate salts. The activity of these metal salt‐supported on four different resins toward hydrogen peroxide decomposition was investigated. The decomposition of H₂O₂, with these catalysts, was found to follow first‐order kinetics with respect to [H₂O₂]. Factors that affected the rate of reaction, such as mesh size of the support, amount of supported salt, and the electrostatic interactions, were investigated. With Ag(I)‐chromate supported on mixed resin MR‐3 in the Ag⁺/NO₃⁻ form, the rate of reaction was greater than that with the mixed resin MR‐12 in the same form. Moreover, the rate with Ag(I) chromate supported on the anion resin IRA‐400 in the R‐NO₃⁻ form was greater than mixed resins. Also, the rate with Fe(III) chromate supported on Amberlite IRA‐400 in the R‐CrO₄²⁻ form was greater than other counter‐anionic forms as well as Dowex‐50W resin in the metal ion form. However, Fe(III)‐chromate supported on cation resin R‐Fe³⁺ showed greater activity than other cationic forms. On the other hand, the rate with MR‐3 resin in the Na⁺/PO₄³⁻ form was greater than that in the presence of supported Fe(III) phosphate. However, the rate of reaction increased when Fe(III) was replaced by Ba(II). Iron(III) phosphate supported on Dowex‐50W resin in the Na⁺ form showed greater activity compared to MR‐3 resin in the Na⁺/PO₄³⁻ form. In the case of Fe(III) phosphate supported on mixed resin MR‐12, the rate was much greater than that with unsupported resin. However, when Ba(II) phosphate was incorporated instead of Fe(III) phosphate, the rate of reaction increased considerably. The activity of Fe(III) chromate is greater than that of Fe(III) phosphate supported on the same cation resin. Activation parameters were evaluated and a probable reaction mechanism was proposed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 667–675, 2000     

Spectroscopic Characterization and Catalytic Activity of Some Cu(II)-thiosemicarbazide Complexes

The complexes of thiosemicarbazide (HTS) have been prepared and characterized by spectral, thermal and magnetic studies. The deprotonation constant of HTS and the formation constants of its complexes were evaluated pH-metrically. The Cu(II) acetate-HTS system gave high stability. The catalytic activity of Co(II), Ni(II) and Cu(II) complexes was tested to decompose H₂O₂. The Co(II) complex has no activity whereas the Cu(II) complex was found to be more active than Ni(II). The different Cu(II) complexes were tested; [Cu₂(TS)(OH)₂(OAc)] was highly active. All parameters affecting the reaction rate (concentration of H₂O₂, weight of catalyst, temperature and pH) were studied and the optimum conditions were evaluated. Attempts to increase the activity of [Cu₂(TS)(HO)₂(OAc)] by mixing with superconducting cuprate sample, Nd_0.1Y_0.9Ba₂Cu₃O_7-δ, will be the subject of further studies.     

Polymer complexes. LXX. Synthesis,spectroscopic studies,thermal properties and antimicrobial activity of metal(II) polymer complexes

The monomer 3‐allyl‐5‐(phenylazo)‐2‐thioxothiazolidine‐4‐one (HL) was prepared by the reaction of allyl rhodanine with aniline through diazo‐coupling reaction. Reaction of HL with Ni(II) or Co(II) salts gave polymer complexes ( 1 – 8 ) with general stoichiometries [M(HL)(Cl)₂(OH₂)₂]_n, [M(HL)(O₂SO₂)(OH₂)₂]_n, [M(L)(O₂NO)(H₂O)₂]_n and [M(L)(O₂CCH₃)(H₂O)₂]_n (where M = Ni(II) or Co(II)). The structures of the polymer complexes were identified using elemental analysis, infrared and electronic spectra, molar conductance, magnetic susceptibility, X‐ray diffraction and thermogravimetric analysis. The interaction between the polymer complexes and calf thymus DNA showed a hypochromism effect. HL and its polymer complexes were tested against bacterial and fungal species. Co(II) polymer complex 2 is the most effective against Klebsiella pneumoniae and is more active than penicillin. The results showed that Ni(II) polymer complex 5 is a good antibacterial agent against Staphylococcus aureus and Pseudomonas aeruginosa. Molecular docking was used to predict the binding between the monomer with the receptors of prostate cancer (PDB code: 2Q7L Hormone) and breast cancer (PDB code: 1JNX Gene regulation). Coats–Redfern and Horowitz–Metzger methods were applied for calculating the thermodynamic parameters of HL and its polymer complexes. The thermal activation energy of decomposition for HL is higher than that for the polymer complexes.     

Catalytic Decomposition of H2O2over Supported ZnO

 Transition metal sulfates of Cu(II), Co(II), Ni(II), Cr(III), Mn(II), and Fe(III) supported on ZnO were prepared and characterized by SEM, EDX, and XRD. The kinetics of the heterogeneous decomposition of H₂O₂ over these supported catalysts was investigated. The reaction rate is correlated with both the amount of supported metal ion and its redox potential. The rate of reaction increases with increasing initial concentration of H₂O₂, attains a maximum, and decreases thereafter. It also increases with pH and reaches a maximum at high pH values. A reaction mechanism is proposed that implies the formation of a peroxo intermediate at the early stages of the reaction. A second intermediate is assumed to be formed at high [H₂O₂]_o which inhibits the progress of the reaction.     

Catalytic Decomposition of H2O2over Supported ZnO

Summary.  Transition metal sulfates of Cu(II), Co(II), Ni(II), Cr(III), Mn(II), and Fe(III) supported on ZnO were prepared and characterized by SEM, EDX, and XRD. The kinetics of the heterogeneous decomposition of H₂O₂ over these supported catalysts was investigated. The reaction rate is correlated with both the amount of supported metal ion and its redox potential. The rate of reaction increases with increasing initial concentration of H₂O₂, attains a maximum, and decreases thereafter. It also increases with pH and reaches a maximum at high pH values. A reaction mechanism is proposed that implies the formation of a peroxo intermediate at the early stages of the reaction. A second intermediate is assumed to be formed at high [H₂O₂]_o which inhibits the progress of the reaction. Received April 26, 2000. Accepted (revised) August 24, 2000     

Decomposition of a cation exchange resin with hydrogen peroxide

Ion exchange resins are widely used in the field of nuclear industry. The present work aimed at the development of a method for complete decomposition of cation exchange resins with H₂O₂ in the presence of Fe³⁺ ion. The decomposition reaction proceeded at ambient temperature and decomposition time was greatly shortened with increasing concentration of Fe³⁺ ion rather than that of H₂O₂. The catalytic action of Fe³⁺ ion was suppressed with increase of HNO₃ concentration. As much as 4 g of the air-dried resin could be decomposed with 8 ml of 30% H₂O₂, and the use of about 60 ml of 30% H₂O₂ resulted in the complete decomposition of organic carbon to CO₂. Absence of any orgnaic carbon in the residual solution will simplify the final disposal.     

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.     

Complex of copper(II) with phenoxo and hexamethylphosphoramide ligands and its decomposition

The 2,4,6-trichlorophenoxo–hexamethylphosphoramide(HMPA)–copper(II) complex was isolated by the reaction of copper(II) chloride with 2,4,6-trichlorophenol, sodium methoxide, and HMPA in methanol solvent under an atmosphere of nitrogen. This complex has the composition of Cu·HMPA·2(C₆H₂Cl₃O). The molecular weight determination was consistent with the copper(II) complex of binuclear structure. The infrared, electronic, and ESR spectra and magnetic susceptibility of the copper(II) complex are discussed in relation to its structure. Decomposition of the copper(II) complex in refluxing benzene yielded poly(dichlorophenylene oxide), coupling product of the 2,4,6-trichlorophenoxo ligand of the copper(II) complex. Electron spin resonance (ESR) measurements on the copper(II) complex in the solid state in a degassed sealed tube at 120 ± 5°C indicated that the phenoxy radical was generated during the period of decomposition and the intensity of the ESR spectra based on copper(II) ion decreased with the measurement time. From these ESR spectra, a possible initial step involving one electron transfer of the decomposition of the 2,4,6-trichlorophenoxo–HNPA–copper(II) complex is discussed.     

Effect of Cu(II)/H2 Salen complex on the non-conventional initiated emulsion polymerization of acrylonitrile

Radical polymerization of acrylonitrile was carried out in an emulsifier-free condition initiated by KHSO₅ catalyzed with Cu(II)/bis-salicylidene ethylene diamine (H₂ Salen) complex. The Cu(II) salt alone, Cu(II)/salicylaldehyde and Cu(II)/ethylene diamine have a retarding effect on the polymerization reaction, while the chelate of Cu(II) with the tetradentate Schiff base ligand, H₂ Salen has a catalytic effect. Prior to this, the catalytic effect of various bivalent transition metal salts and their couple with the Schiff base, H₂ Salen on the polymerization reaction has been examined to be not significant. The in situ developed complex produces the stable emulsion leading to high conversion. In the polymerization, the variables studied were the concentration of monomer, initiator, Cu(II), H₂ Salen and temperature. The overall activation energy was computed to be 13.1 kcal/mol. From the kinetic and spectral analyses, the mechanism of the initiator decomposition and initiation of polymerization by Cu(II)/H₂ Salen complex were suggested. The rate of polymerization (R_p) was found to be dependent on the monomer, initiator, Cu(II) ion, H₂ Salen concentrations to the 1.4, 0.3, 1.6, 1.5 power respectively. The polymers are characterized by IR and molecular weight by viscosity and GPC methods.     

A New Oscillating Reaction of the Belousov-Zhabotinskii-type with a Macrocyclic Copper(II) Complex as Catalyst

The reaction of bromate ion with malic acid in aqueous H₂SO₄ catalyzed by a tetraazamacrocyclic copper(II) complex exhibits oscillatory behavior. This complex contains an unsaturated macrocyclic ligand, 5,7,7,12,14,14-hexemethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. The reactions were monitored both spectrophotometrically and potentiometrically. It was found that the oscillation period (tp) is dependent on the initial concentrations of malic acid or H₂SO₄ but is independent of the initial concentrations of NaBrO₃. The experimental results indicate that acrylonitrile, H₂O₂, vitamin C, glucose or CCl₄ present in the system can inhibit the oscillations. A tentative mechanism is proposed.     

Thermolysis of copper(II) salts of maleic acid. Synthesis of metal-polymer composites

The thermal decomposition of neutral ([Cu(H₂O)(C₄H₂O₄)]) and acidic ([Cu(H₂O)₄](C₄H₃O₄)₂) maleates can conventionally be divided into four stages: (1) dehydration, (2) polymerization, (3) isomerization of the maleate ion to the trans form with the simultaneous reduction Cu(II) → Cu(I), and (4) decarboxylation of copper(I) fumarate. The third and fourth stages of the decomposition of these salts coincide. The residue after the thermolysis of copper(II) maleates in a He flow is a composite consisting of aggregates from 50 nm to several microns in size. Spherical conglomerates (50–200 nm) containing many spherical Cu particles (5–10 nm) are incorporated into the organic polymer matrix of these aggregates.     

Maleates of Mn(II), Fe(II), Co(II), and Ni(II) as precursors for synthesis of metal-polymer composites

Comparison was made for the structural, IR spectral, and thermoanalytical characteristics of normal [M₁(H₂O)₂(C₄H₂O₄)](H₂O) (M₁ = Co(II) and Ni(II)) and acid maleates [M₂(H₂O)₄(C₄H₃O₄)₂] (M₂ = Mn(II), Fe(II), Co(II) and Ni(II)). Only structures of acid maleates contain intramolecular asymmetric hydrogen bond whose asymmetry increases in the series of transition metal salts. Thermal decomposition of Co(II), Ni(II) normal maleates, and Mn(II), Fe(II), Co(II), Ni(II) acid maleates proceeds in three stages. Onset decomposition temperatures for the first and second stages decreases in the series of normal maleates Co(II) ≥ Ni(II) and increases in the series of acid maleates Fe(II) < Co(II) < Ni(II) ≈ Mn(II). Onset temperature of the third stage decreases in the series of both normal maleates Co(II) > Ni(II) and acid maleates Mn(II) > Fe(II) > Co(II) > Ni(II).