Catalytic behavior of copper(II) chelate complexes sterically held in zeolite large cavities and fixed on its outer surface by a topological anchor

Catalytic properties of copper(II) tricyclic chelate compounds based on enamino ketone of 3-acetyl-2,4-pentanedione and 1,6-hexametylenediamine fixed on NaY and CaA zeolites by the methods of topological and topologically-anchor retention, respectively, were compared. The mode of fixation of chelates on a support affects the character of the liquid-phase catalytic oxidation of cyclohexene by molecular oxygen. At the topological fixation by a steric retention of a chelate compound in a large cavity of NaY zeolite, the reaction rate related to one reaction center of a metal complex is not proportional to the filling degree that points to inaccessibility for a substrate of catalyst molecules localized in inner cavities of crystallites. In an alternative mode of the catalyst topologically-anchor fixation, when only a ligand fragment is held in CaA zeolite, and catalytically active metal center is turned to the side of the reaction medium, the linear dependence of the cyclohexene oxidation rate on the amount of the chelate on the support is retained within the whole studied range of the surface catalyst concentrations. The catalytic activity of the topologically-anchor fixed Cu(II) chelate compound coincides with its activity in the zeolite absence, which points to a pseudo-homogeneous mode of cyclohexene oxidation. At topologically-anchor fixation of a Cu(II) chelate compound on CaA zeolite diffusion limitations characteristic for the fixation by steric retention are completely eliminated.     

Metal chelates in vinyl polymerization: Kinetics and mechanism of acrylonitrile polymerization initiated by Cu(II) imine complexes

The free radical polymerization of acrylonitrile (AN) initiated by Cu(II) 4-anilino 2-one [Cu(II) ANIPO] Cu(II), 4-p-toluedeno 3-pentene 2-one [Cu(II) TPO], and Cu(II) 4-p-nitroanilino 3-pentene 2-one [Cu(II) NAPO] was studied in benzene at 50 and 60°C and in carbon tetrachloride (CCl₄), dimethyl sulfoxide (DMSO), and methanol (MeOH) at 60°C. Although the polymerization proceeded in a heterogeneous phase, it followed the kinetics of a homogeneous process. The monomer exponents were ≥2 at two different temperatures and in different solvents. The square-root dependence of R_p on initiator concentration and higher monomer exponents accounted for a 1:2 complex formation between the chelate and monomer. The complex formation was shown by ultraviolet (UV) study. The activation energies, kinetics, and chain transfer constants were also evaluated.     

Catalytic properties of platinum(II) immobilized on polymethylene sulfide in the hydrosilylation reaction

Hydrosilylation of 1,1,3,3-tetramethyl-1,3-divinyldisiloxane with 1,1,3,3-tetramethyldisiloxane in the presence of platinum(II) immobilized on polymethylene sulfide is studied.     

Estimation of stability constants of copper(II) and nickel(II) chelates with dipeptides by using topological indices

The estimation of the overall stability constants β₁ of copper(II) and nickel(II) chelates with dipeptides was performed by using the model with the valence connectivity index of the 3rd order (³χ^v). It was done by dividing β₁ to its constituting constants K₁ and K_a, and subsequently by dividing the basic set into subsets or treating the chelate rings as separate units. Altogether 15 copper(II) and eight nickel(II) chelates with dipeptides were investigated. Six models for the estimation of log K₁ and pK_a were checked, most of them by usage of indicator variables (for differentiation of copper(II) and nickel(II) complexes or subclasses of ligands). Estimates of log β₁ gave the range of rms values from 0.19 to 0.27. For the best model, errors of estimates were less than 0.34.     

Metal chelates in vinyl polymerization: Bulk polymerization of acrylonitrile initiated by Cu(II)–imine complexes

This article deals with the kinetics and mechanism of acrylonitrile (AN) polymerization initiated by Cu(II)–4-anilino 3-pentene 2-one[Cu(II)ANIPO], Cu(II)–4-p-toluedeno 3-pentene 2-one [Cu(II)TPO], and Cu(II)–4-p-nitroanilino 3-pentene 2-one [Cu(II)NAPO] in bulk at 60°C. The polymerization is free radical in nature. The exponent of initiator(I) is ? 0.5. The initiation step is a complex formation between the chelate and monomer and subsequent decomposition of the intermediate complex giving rise to free radical and Cu(I). This is substantiated by ultraviolet (UV) and electron spin resonance (ESR) studies. The activation energies and kinetic and chain transfer constants have also been evaluated.     

Thermal study of Cu(II), Ni(II) and Pd(II) chelates of resacetophenoneoxime

Summary Thermal analysis of resacetophenoneoxime and its chelates of Cu(II), Ni(II) and Pd(II) is carried out. A comparison is made between the thermal stability and the solution stability of chelates and found that they oppose each other. The thermal stability for the chelates studied is PdNi>Cu and the solution stability on the other hand is Pd>Cu>Ni. The results obtained were compared with the data available in the literature for structurally similar oximes. The advantages of the reagent for gravimetric and thermogravimetric analysis of metal ions were discussed.

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Thermochemische Untersuchung der Cu(II)-, Ni(II)- und Pd(II)-Chelate von Resacetophenonoxim

Zusammenfassung Die thermische Stabilität der Chelate und ihre Stabilität in Lösung wurden verglichen und festgestellt, daß diese sich nicht entsprechen. Die erste nimmt ab in der Reihenfolge PdNi>Cu, die zweite in die Reihenfolge Pd>Cu>Ni. Die erhaltenen Ergebnisse wurden denen aus der Literatur für strukturell ähnliche Oxime gegenübergestellt. Die Vorteile des Reagenses für gravimetrische und thermogravimetrische Bestimmungen werden diskutiert.

     

Thermodynamic stability of Ni(II) and Cu(II) chelates with biladiene-a,c in DMF

The equilibria of the reactions of complex formation between alkyl-substituted biladiene-a,c and Ni(II) and Cu(II) acetates in DMF were studied by the electronic spectroscopy. Porphyrin-like complexes (1:1) were shown to form in the systems under study. Concentration constants of complex formation were calculated and extrapolated to infinite dilution in order to obtain standard thermodynamic quantities. The role of the nature of a metal cation on thermodynamic parameters of complex formation processes was discussed.     

Studies of Co(II), Ni(II), Cu(II) and Cd(II) chelates with different phosphonic acids

Co(II), Ni(II), Cu(II) and Cd(II) chelates with 1-aminoethylidenediphosphonic acid (AEDP, H₄L¹), α-amino benzylidene diphosphonic acid (ABDP, H₄L²), 1-amino-2-carboxyethane-1,1-diphosphonic acid (ACEDP, H₅L³), 1,3-diaminopropane-1,1,3,3-tetraphosphonicacid (DAPTP, H₈L⁴), ethylenediamine-N,N′-bis(dimethylmethylene phosphonic)acid (EDBDMPO, H₄L⁵), O-phenylenediamine-N,N′-bis(dimethyl methylene phosphonic)acid (PDBDMPO, H₄L⁶), diethylene triamine-N,N,N′,N′,N″N″-penta(methylene phosphonic)acid (DETAPMPO, H₁₀L⁷) and diethylene triamine-N,N″-bis(dimethyl methylene phosphonic)acid (DETBDMPO, H₄L⁸) have been synthesised and were characterised by elemental and thermal analyses as well as by IR, UV–VIS, EPR and magnetic measurements. The first stage in the thermal decomposition process of these complexes shows the presence of water of hydration, the second denotes the removal of the coordinated water molecules. After the loss of water molecules, the organic part starts decomposing. The final decomposition product has been found to be the respective MO·P₂O₅. The data of the investigated complexes suggest octahedral geometry with respect to Co(II) and Ni(II) and tetragonally distorted octahedral geometry with respect to Cu(II). Antiferromagnetism has been inferred from magnetic moment data. Infrared spectral studies have been carried out to determine coordination sites.     

Hetero-binuclear chelates of Mn(II), Co(II) and Cu(II) o-cresolphthalein complexonates with other metal ions

Heterobinuclear metal chelates of Mn²⁺, Co²⁺ or Cu²⁺ and some transition metal ions with o-cresolphthalein complexone have been prepared and characterized. Elemental analyses are in agreement with proposed formulae. Thermal analyses (TGA and DTA) were used to determine the degradation products; some thermodynamic parameters were calculated. IR and UV-Vis spectra identified the mode of bonding between the metal ions and the ligand as well as its geometry. Magnetic moment determination and ESR spectra of the heterobinuclear complex revealed some antiferromagnetic interaction between the metal ions, which depends mainly on the two metal ions forming the chelate. Electrochemical studies of the complexes [DC-polarography and cyclic voltammetry (CV)] confirmed the existence and the nature of the metal ions in the chelate.     

Cu(0) nanoclusters derived from poly(propylene imine) dendrimer complexes of Cu(II).

A family of diaminobutane core, poly(propylene imine) dendrimers coordinated to Cu(II), DAB-Am(n)-Cu(II)x (n = 4, 8, 16, 32, 64, x = n/2), was studied by means of extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) spectroscopies. The geometry of the dipropylene triamine (dpt)-Cu(II) end-group complexes for all dendrimer generations is reported for the first time and is found to be that of a square-based pyramid with each Cu ion bound to three nitrogen atoms (Cu-N distance approximately 2.03 A) of the dpt end group of the dendrimer. An oxygen atom residing 1.96 A from the Cu ion also occupies the equatorial plane, and the pyramid is completed by an axial oxygen at approximately 2.65 A. In addition, we report for the first time that reduction of the Cu(II)-dendrimer complexes with NaBH4 yields DAB-Am(n)-Cu(0)(cluster) species. Transmission electron microscopy (TEM) studies of the reduced species demonstrate that there is a systematic decrease in the size of the generated Cu clusters with increasing dendrimer generation. Additionally, it was found that the size of the nanoclusters is a function of the n/x ratio of the DAB-Am(n)-Cu(II)x precursor, with highly monodisperse, extremely small nanoclusters (r(cluster) = 8.0 +/- 1.6 A) obtained with n = 64 and x = 16. EXAFS and XANES measurements on the reduced DAB-Am(n)-Cu(0)(cluster) corroborate the TEM data, and provide additional information on the possible encapsulation of the Cu nanoclusters by the dendrimers.     

Ternary complexes of the Cu(II) and Ni(II) chelates of edta and dcta with cyanide and ethylenediamine

The formation of the ternary complexes CuEDTA(en)(2-), CuEDTA(CN)(3-), CuDCTA(CN)(3-), NiDCTA(CN)(3-) and NiEDTA(en)(2-) has been established spectrophotometrically. The stability constants found were log K = 2.87 +/- 0.03, 3.76 +/- 0.06, 2.64 +/- 0.35, 2.41 +/- 0.21 and 2.74 +/- 0.35 respectively. For the system CuDCTA(2-) + en no ternary complex was observed, instead Cu(en)(2)(2+) was formed. No reaction was found for the systems CoEDTA(2-) + N(3)(-), CoDCTA(2-) + N(3)(-), NiDCTA(2-) + en, NiDCTA(2-) + phen, NiEDTA(2-) + phen, NiDCTA(2-) + N(3)(-), NiEDTA(2-) + N(3)(-), CrEDTA(-) + NH(3), CrEDTA(-) + CN(-), CuEDTA(2-) + N(3) and CuEDTA(2-) + N(3)(-). The systems CoEDTA(2-) + en and CoDCTA(2-) + en involve more than one equilibrium. The absorption spectra of the ternary complexes between 500 and 850 nm are reported.     

Poly(ethylene imine) hybrids containing polyhedral oligomeric silsesquioxanes: Preparation, structure and properties

Both octaglycidyletherpropyl polyhedral oligomeric silsesquioxane and hepta(3,3,3-trifluoropropyl)glycidyletherpropyl polyhedral oligomeric silsesquioxane were synthesized via the hydrosilylation reactions between octahydrosilsesquioxane [and/or hepta(3,3,3-trifluoropropyl)hydrosilsesquioxane] and allyl glycidyl ether. The polyhedral oligomeric silsesquioxane (POSS) macromers were characterized by means of Fourier transform infrared and nuclear magnetic resonance spectroscopy. The inter-component macromolecular reactions between the POSS macromers and poly(ethylene imine) (PEI) were employed to prepare the POSS-containing organic-inorganic PEI hybrids. The inclusion of octaglycidyletherpropyl POSS into PEI results in the formation of the organic-inorganic hybrid networks whereas the introducing hepta(3,3,3-trifluoropropyl)glycidyletherpropyl POSS to PEI affords the linear POSS-grafted PEI copolymers. Differential scanning calorimetry and thermogravimetric analysis show that the POSS-containing PEI hybrids displayed increased glass transition temperatures (T_g’s) and enhanced thermal stability compared to the plain PEI. These PEI hybrid composites can be significantly swollen with water without dissolving, suggesting the formation of hydrogels. The PEI hydrogels containing octaglycidyletherpropyl POSS is in reality the chemically-crosslinked hydrogels whereas the those containing hepta(3,3,3-trifluoropropyl)glycidyletherpropyl POSS displayed the behavior of physical hydrogels. The formation of physical hydrogels is ascribed to the microphase-separated morphology in the hybrids. In addition, the hybrids containing hepta(3,3,3-trifluoropropyl)glycidyletherpropyl POSS exhibited the typical amphiphilicity as evidenced by the increase in surface hydrophobilicity.     

Synthesis and liquid crystal properties of copper(II) and palladium(II) chelates with new ferrocene-containing enaminoketones

Heterometallic liquid crystals are of special interest because of the possibility to combine optical, magnetic and electric properties of different metal ions in one mesogenic molecule. In order to investigate new heteropolynuclear mesogenic systems, a series of β-aminovinylketone ligands derived from acetyl ferrocene have been synthesized. Subsequently Cu(II) and Pd(II) ions were incorporated into the enaminoketone chelate core. The obtained ligands and complexes were characterized by element analysis, ¹H NMR, IR and UV–Vis spectroscopies. According to thermal polarizing microscopy and DSC studies, the ligands and Cu(II) complexes exhibit disordered soft crystal phases upon cooling from the isotropic liquid state. The Pd(II) complexes showed monotropic smectic C mesomorphism. The metal centres in the synthesized heteropolynuclear mesogens are in close vicinity to each other, which is of considerable interest from the viewpoint of the potential electron-transfer interactions between a ferrocene core and the central ions.     

Encapsulation of Fe(III) and Cu(II) complexes in NaY zeolite

The use of nonporphyrin complexes encapsulated in zeolites as catalysts for oxidation reactions has been improved in the past decades by the discovery of increasing numbers of nonheme monoxygenases. The zeolite lattice can change the oxidative chemistry of the metallocomplexes, resulting in a catalytic effect different from those observed in homogeneous reactions. We report the encapsulation of iron and copper metallocomplexes with the ligand (2-hydroxybenzyl)(2-methylpyridyl)amine, Hbpa, and iron complexes with the ligand N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-methylpyridyl) ethylenediamine, H(2)bbpen. The zeolite-encapsulated metallocomplexes were prepared by diffusion of the ligands through the pores of the zeolites, already exchanged with the respective metal. The syntheses were performed in methanol and toluene solutions. Elemental analysis of solids with the Hbpa ligand have indicated better complexation for synthesis in toluene, where 74% of the iron atoms were coordinated by the ligand, against 37% for the synthesis in methanol. For the immobilization with the H(2)bbpen ligand in toluene it was observed that 46% of the iron atoms are coordinated, showing that the diffusion of the small ligand Hbpa through the zeolite cage was facilitated. The EPR spectra of the solids show signals at g = 2.0, which was attributed to an Fe-Fe interaction from the noncoordinated atoms, and g = 4.3 attributed to iron (III) in a rhombic geometry.     

A trinucleating ligand based on 1,8-naphthalenediol: synthesis, structural and magnetic properties of a linear Cu(II)Cu(II)Cu(II) complex

The extension of Robson-type ligands from dinucleating based on 2,6-diformylphenol to trinucleating based on 2,7-diformyl-1,8-naphthalenediol is demonstrated by the synthesis, structural and magnetic characterization of the first trinuclear Cu(II) complex using a 1,8-naphthalenediol derived ligand.     

Sequestration of Cu(II), Ni(II), and Co(II) by ethyleneimine immobilized on silica

Thermodynamic data on interaction of Cu(II), Ni(II), and Co(II) with silica modified with ethyleneimine are obtained by calorimetric titration. The amount of ethyleneimine anchored on silica surface was estimated to be 0.70 mmol g⁻¹. The enthalpies of binding Ni(II), Cu(II) and Co(II), are −3.59 ± 0.001, −4.88 ± 0.001, and −7.75 ± 0.003 kJ mol⁻¹, respectively.     

Heterogenization of palladium(II) chelates on a sibunite

Summary Heterogenized palladium(II) chelates have been prepared by a sibunite treatment of acetone or aqueous solutions of palladium complexes with alizarin red C, 4- anilino-pent-3-en-2-one,N, N-bis(acetylacetone)ethylenediamine, 1-phenyl-4-methylpent-4-en-1,3-dione and 1-phenyl-3-anilino-4-methylpent-4-en-1-one. The catalytic properties of these chelates in chloronitrobenzene hydrogenation have been studied. It was found that the catalytic activity approaches 159 mol H₂ (mol Pd min)^–1 depending on the chlorine atom position in the aromatic ring and the nature of the solvent. The catalysts do not lose their activity after five cycles. The products of chloronitrobenzene hydrogenation are chloroanilines (up to 90%), azo- and azoxychlorobenzenes (5–7%) as a result of incomplete reduction as well as small quantities (2–5%) of dehalogenated azo-, azoxybenzenes and aniline.     

Catalytic determination of Pb(II) in the presence of Cu(II)

A kinetic method is presented to determine micro-molar amounts of Pb(II) from various river and wastewater samples, in the presence of trace copper. The procedure is based on the catalytic effect of both species on the oxidation of mercaptosuccinic acid by chromate in acidic media. The extent of the reaction is followed spectrophotometrically at 420 nm and pseudo-first-order rate coefficients of the rate-determining step are determined as a function of catalyst concentrations. The optimum operating conditions (ionic strength, temperature, and concentration of reagents) regarding sensitivity towards lead were established. Interference by several ionic species has been studied. The effect of Fe(III), the only severe interferent, is suppressed by complexation with 1,10-phenantroline. The bi-component calibration model employs an artificial neural network to compute the Pb(II) concentration from a k(obsd) value and the a priori-known Cu(II) concentration of the sample. Working concentration ranges are 20-2160 micro g L(-1) for Pb(II) and 80-650 micro g L(-1) for Cu(II), respectively. Detection limits are 20 micro g L(-1) Pb(II) and 80 micro g L(-1) Cu(II), respectively. The relative standard deviations (3 measurements) for four different testing points are lower than 2.5%. The method was applied to samples of river and wastewater of the mining region of Baia-Mare, Northern Romania. The results were compared to those obtained by an officially standardized AAS method. Good agreement was achieved. The method is inexpensive, fairly rapid, and sensitive. Its working range covers the exact range of concentrations usually encountered in the mentioned geographic area.