Interaction of manganese(II) with methyl salicylate ethyl salicylate and phenyl salicylate

The proton ligand stability constants of methyl salicylate, ethyl salicylate and phenyl salicylate and the stepwise stability constants of manganese(II) complexes with these have been determined potentiometrically in aqueous ethanol system 50/50 (v/v) at 25°C at different ionic strengths, viz. 0.050 M, 0.075 M, 0.100 M and at 35 and 45°C at an ionic strength of 0.05 M. The thermodynamic stability constants of the complexes have been evaluated from the various values by extrapolating to zero ionic strength at 25°C. The thermodynamic parameters such as free energy changes (ΔG), enthalpy changes (ΔH) and entropy changes (ΔS) involved have been calculated.     

Kinetics and Equilibria for Complex Formation between Palladium(II) and Chloroacetate

Kinetics and equilibria for the formation of a 1:1 complex between palladium(II) and chloroacetate were studied by spectrophotometric measurements in 1.00 mol HClO₄ at 298.2 K. The equilibrium constant, K, of the reaction

Formation of protonated salicylate complexes of Cd(II) and Zn(II)

The formation constants of the protonated complexes of Cd(II) and Zn(II) with salicylic acid (H₂Sal) and the equilibrium constants for the extraction of these complexes into cyclohexane containing tributyl phosphate (TBP) have been determined. For the complex formation:

log K₁₁ is 1.9 for Cd(II) and 1.4 for Zn(II) at 30°C and 0.1 M NaClO₄. For the extraction:

log K_ex is ?1.6 for Cd(1I) and ?2.2 for Zn(II).     

Kinetics and mechanism of complex formation between beryllium(II) and the 3-nitrosalicylatopentaamminecobalt(III) ion

Summary The kinetics of formation and dissociation of the binuclear complex of Be²⁺ with 3-nitrosalicylatopentaamminecobalt(III) have been investigated in the 20–40 and 25–40 °C ranges (I = 0.3 mol dm ^–3), respectively. At 25 °C the rate and activation parameters for the formation of the binuclear species are: k _f = 26.9 × 10² dm³mol^–1s^–1, H = 104 ± 7kJ mol^–1 S = 91 ± 22JK^–1mor^–1.The rate constant, activation enthalpy and activation entropy for the acid-catalysed dissociation of the binuclear species are: 1.25 ± 0.08dm³mol ^–1 at 25 °C, 53 ± 3kJ mol^–1 and - 67 ± 9 J K ^–1 mol^–1, respectively. The formation of the binuclear species is chelation controlled while the dechelation is acid catalysed.     

Interactions between Co(III) and Ni(II) complex ions and polyelectrolytes

An investigation has been carried out of the interaction of optically active tris(ethylenediamine)–Co(III) and of tris(o-phenanthroline)–Ni(II) complex ions with different polyelectrolytes in dilute aqueous solution. Optical rotatory dispersion measurements reveal that binding of the Co(III) complex ions occurs with a noticeable degree of specificity which in addition to depending on the nature of the fixed charges is also affected by the chemical constitution of the polyelectrolytes chain backbones. The dependence of tris(ethylenediamine)–Co(III) optical activity on polyelectrolyte concentration also exhibits interesting features. Polarimetric measurements of the rate of racemization of tris(o-phenanthroline)–Ni(II) ions in the presence of different polyelectrolytes lead to similar conclusions. Sodium dextran sulfate is shown to interact selectively with one of the antipodes of tris(phenanthroline)–Ni(II) complex.     

Bis(perfluoroalkyl and aryl substituted acetylacetonate)beryllium(II) chelates

The synthesis of eight beryllium chelates having substituted beta-diketone ligands, RCOCH₂COR′, is reported (R=methyl, 2′-thienyl, 2′- furyl, phenyl; R′=CF₃, C₂F₅, C₃F₇). ¹³C, ¹⁹F and ¹H NMR spectra data are compared to give a shielding order. These four-coordinate pseudo- tetrahedral complexes of idealized C₂ symmetry all give a more deshielded ring carbon than the corresponding ring carbon resonances of the same ligand in four-coordinate square planar complexes. Some dipole moment data are also presented.     

Thermodynamics of interactions between lead(II) and cadmium(II) ions and azulene-based complexing polymer films

In order to understand the essential processes/interactions between the metal ions and modified electrodes which are based on complexing polymeric films, access to thermodynamic characteristics is compulsory. The paper enlarges the information concerning the sorption of metal ions within complexing polymer films, particularly based on azulene, which can be involved in metal detection sensors. Interactions between lead(II) or cadmium(II) ions and complexing polymer films have been studied using chemical preconcentration–anodic stripping method. The films have been obtained by controlled potential electrolysis in millimolar solutions of 4-azulen-1-yl-2,6-bis(2-thienyl)pyridine (L) in acetonitrile. PolyL films affinities towards these metal ions have been quantified at different temperatures by means of sorption isotherms. Parameters for sorption of lead(II) and cadmium(II) ions within polyL films have been calculated for Freundlich, Langmuir and Redlich–Peterson isotherms. The best fit was obtained when using Langmuir isotherm. The results evidence that lead ions are better sorbed than cadmium within polyL film. Thermodynamic parameters for the chemical sorption of lead(II) and cadmium(II) ions within polyL films have been calculated.     

Heat effects of complex formation between maleic acid and zinc(II) and nickel(II) ions

The heat effects of formation of zinc(II) and nickel(II) complexes with maleic acid were determined by the direct calorimetric method at 298.15 K and several ionic strength values against the background of NaNO₃. The standard thermodynamic characteristics of complex formation in aqueous solution were calculated.     

Equilibria and kinetics of complex formation between copper(II) and the polyamine Me2octaen

The kinetics and the equilibria of complex formation between Cu(II) and 1,25-dimethyl-1,4,7,10,13,16,19,22,25-nonaazapentacosane (Me₂octaen) have been investigated in acidic aqueous solution, at an ionic strength of 0.1 mol dm⁻³ and 25°C, by the stopped-flow method and UV spectrometry. Me₂octaen is a linear polyamine made by the union of eight en units bearing two methyl residues at the ends of the chain. Spectrophotometric titrations and kinetic experiments indicated that below pH 2.4 the binding of Cu(II) to the ligand gives rise to several 1:1 complexes differing for their degree of protonation, whereas above pH 2.4 binuclear complexes are formed as well. Concerning the mononuclear species, the ratios of the formation to the dissociation rate constants are in agreement with the equilibrium constants measured by static spectrometry. The analysis of the kinetic and spectrophotometric data reveals that, in the range of pH between 1.7 and 2.4, the most reactive forms of the ligand (denoted in its fully protonated form as H₉L⁹⁺) are H₇L⁷⁺, H₆L⁶⁺, and H₅L⁵⁺. The analysis of the results shows that Cu²⁺ and H₆L⁶⁺ may react according to the internal conjugate base mechanism (ICB), although the observed internal conjugate base effect is more modest than that displayed by the Ni²⁺–Me₂octaen system. The small magnitude of the ICB effect is explained in terms of the enhanced reactivity of copper(II) owing to the Jahn–Teller distortion occurring for Cu²⁺ complexes.     

Equilibria in complexes of N-heterocyclic ligands. Part 33. Ruthenium(II) complex ions with chelating pyridyl-imidazoles

Summary The complex salts [RuL₃] (ClO₄)₂ · nH₂O have been made, where L = 2-(2-pyridyl)imidazole and n = 2 or 2-(2-pyridyl)-benzimidazole, n = 3. Spectra are discussed, including circular dichroism (the complex ions having resulted from asymmetric syntheses).Author to whom correspondence should be directed.     

Extraction of lead(II) and copper(II) from salicylate media by tributylphosphine oxide.

Tributylphosphine oxide (TBPO) is proposed as an extractant for the extraction of lead(II) and copper(II) from salicylate media. The optimum conditions were evaluated by varying the experimental parameters, such as the pH, sodium salicylate concentration, tributylphosphine oxide (TBPO) concentration, shaking period and various diluents. The probable extracted species, deduced from log-log plots were Pb(HSal)2.2TBPO and Cu(HSal)2.2TBPO. The extraction took place through a solvation mechanism. The method permits the binary separation of lead(II) and copper(II) from commonly associated elements as well as the mutual separation of lead(II) and copper(II). The method is applicable to the determination of lead(II) and copper(II) in various alloys as well as environmental and pharmaceutical samples.     

Electrochemical behaviour of aluminium(III) and beryllium(II) perchlorates in dimethylformamide

Well defined voltammetric peaks of A1(III) and Be(II) were obtained in DMF at the HMDE, and the nature of the electrochemical process in this medium was investigated. Adsorption and chemical reaction coupled with the charge transfer were observed in both cases. The optimum depolarizer concentration and scan-rate for analytical determination were established. Close similarities were found in the electrochemical behaviour of Al(III) and Be(II), and differences were in degree rather than of kind.     

Equilibria in aqueous solution between Be(II) and iminodiacetic,N-methyliminodiacetic,N-ethyliminodiacetic and N-propyliminodiacetic acids

The complex species formed in aqueous solution between Be(II) and iminodiacetic, N-methyliminodiacetic, N-ethyliminodiacetic and N -propyliminodiacetic acids were studied at 25°C and ionic strength 0.5 M in Na ClO₄. The application of the least-squares computer program LETAGROP to the experimental potentiometric data, taking into account hydrolysis of the Be(II) ion, indicates that, upon varying the ligand-metal relationship, only the monohydroxide complex [Be(OH)C]⁻ (H₂C ligand) is formed in significant amounts for the four systems studied. The formation constants β_pr (11, − 11 and −21) of the protonated species of the ligands, β_pq(− 12 and − 33) of the hydrolytic species of Be(II), and β_pqr(− 311) of the complex [Be(OH)C]⁻ were determined.     

Solvent effects upon reactions between ions: hexacyanoferrate(II)-peroxodisulphate and sulphite-hexacyanoferate(III)

Summary Different approaches to the interpretation of solvent effects on reactions between ionic reactants are analysed, taking as a basis the kinetic data corresponding to the sulphite-hexacyanoferrate(III) and peroxodisulphate-hexacyanoferrate(III) oxidations. It is concluded that the approach based on the use of solvent parameters is the more promising, although knowledge of the transfer chemical potentials of the reactants may also be useful in the interpretation of kinetic behaviour.     

Electrometric study of uranyl(II) and beryllium(II) complexes of 2,2′-dimercapto diethyl ether

Complexation of uranyl(II) and beryllium(II) ions with 2,2′-dimercaptodiethyl ether has been studied in 40% ethanolic media by potentiometric and conductometric titration techniques revealing the formation of an 1∶1 complex in either case. The stability constants of the complexes have been determined at ionic strength μ=0.1M (NaClO₄) by applyingCalvin andMelchior's extension ofBjerrum's method. LogK _stab values are found to be 12.60, 11.96 at 25 °C and 12.55, 11.90 at 35 °C respectively. The values of ΔG, ΔH and ΔS for the complexation reactions determined at 25 °C are also reported.