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 . dm(-3) HClO4 at 298.2 K. The equilibrium constant, K, of the reaction Pd2+ + HL reversible arrow PdL+ + H+ was determined from multi-wavelength absorbance measurements of equilibrated solutions at variable temperatures as log(10)K (298.2K) = 0.492 +/- 0.006 with Delta H-o = - 15.6 +/- 1.9 kJ . mol(-1) and Delta S-o = -43.0 +/- 6.3 J . K-1, mol and spectra of individual species were calculated. Variable-temperature kinetic measurements gave rate constants for the forward and backward reactions at 298.2 K and ionic strength 1.00 mol . dm(-3) as k(1) = 6.46 +/- 0.08 dm(3) . mol(-1) . s(-1) and k(-1) = 2.91 +/- 0.03 s(-1), with activation parameters Delta H-1(not equal) = 56.55 +/- 0.75 kJ . mol(-1), Delta S-1(not equal) = -40.0 +/- 2.5 J . K-1 mol(-1), Delta H--1(not equal) = 64.42 +/- 0.50 kJ . mol(-1) and Delta S--1(not equal) = -20.3 +/- 1.7 J . K-1 . mol-1, respectively. From the kinetics of the forward and reverse processes, log(10) K = 0.346 +/- 0.007, Delta H-o = -7.9 +/- 0.9 kJ . mol(-1) and Delta S-o = - 19.8 +/- 3.0 J . K-1 . mol(-1) were derived, and these values are in good agreement with the results of the equilibrium measurements. The Specific Ion Interaction Theory was employed for determination of thermodynamic equilibrium constants for the protonation of chloroacetate (log(10) K-p(o) = 2.857 +/- 0.016) and formation of the PdL+ complex (log(10) K-o = 1.002 +/- 0.046, log(10) beta(o) = 3.859 +/- 0.048). Specific ion interaction coefficients epsilon(L-, Na+) = 0.042 +/- 0.022 kg . mol(-1), epsilon(L-, K+) = 0.081 +/- 0.021 kg . mol(-1), epsilon(PdL+, ClO4-) = 0.92 +/- 0.21 kg . mol(-1) were derived

Thermodynamics for complex formation between palladium(II) and oxalate

Complex formation between [Pd(H2O)(4)](2+) and oxalate (ox = C2O42-) has been studied spectrophotometrically in aqueous solution at variable temperature, ionic strength and pH. Thermodynamic parameters at 298.2 K and 1.00 mol dm(-3) HCIO4 ionic medium for the complex formation [Pd(H2O)(4)](2+) + H(2)ox (sic) Pd(H2O)(2)(ox)] + 2H(3)O(+) with equilibrium constant K-1H (in mol dm(-3)) are logio K-1,K-H = 3.38 +/- 0.08, Delta H-1(0) = -33 +/- 3 kJ mol(-1), and Delta S-1(0) = 48 +/- 11 J K-1 morl, as determined from spectrophotometric equilibrium titrations at 15.0, 20.0, 25.0 and 31.0 degrees C. Thermodynamic overall stability constants beta(0)(n) (in (mol dm-(3))(-n), n = 1,2) for [pd(H2O)(2)(ox)] and [Pd(ox)(2])(2) at zero ionic strength and 298.2 K, defined as the equilibrium constants for the reaction Pd2+ nox(2) (sic) Pd(ox)](2-2n) (water molecules omitted) are logio beta(0)(1) = 9.04 +/- 0.06 and logio beta(0)(1) = 13.1 +/- 0.3, respectively, calculated by use of Specific Ion Interaction Theory from spectrophotometric titrations with initial hydrogen ion concentrations of 1.00, 0.100 and 0.0100 mol dm-3 and ionic strengths of 1.00, 2.00 or 3.00 mol dm-3. The values derived together with literature data give estimated overall stability constants for Pd(o) compounds such as Pd(en)(ox)1 and cis-IPd(NH3)2021, some of them analogs to Pt(s) complexes used in cancer treatment. The palladium oxatato complexes are significantly more stable than palladium(v) complexes with monodentate 0-bonding ligands. A comparison between several different palladium complexes shows that different parameters contribute to the stability variations observed. These are discussed together with the so-called chelate effect

Comment on “Hypersensitive Luminiscence of Eu³⁺ in Dimethyl Sulfoxide As a New Probing for Water Measurement”

Comment on “Hypersensitive Luminiscence of Eu³⁺ in Dimethyl Sulfoxide As a New Probing for Water Measurement

Kinetic study of dissociation of a copper(II) complex of a 14-membered tetraaza-macrocyclic ligand containing pyridine and pendant N-carboxymethyl arms

The kinetics of acid-catalyzed dissociation of the copper(II) complex with 7-methyl-3,7,11,17-tetraazabicyclo[11.3.1] heptadeca-1(17), 13,15-triene-3,11-diacetic acid (ac(2)Me[14] pyN(4)) at [H+] = 0.05-0.25 mol l(-1), I = 0.25 mol l(-1) (Na, H) ClO4, and T = 298.16 K was studied with conventional and stopped-flow UV/VIS spectroscopy. Three steps of consecutive complex reaction were observed. The very fast first and second steps characterized by k(1) = 70 +/- 10 and k(2) = 0.23 +/- 0.01 l mol(-1) s(-1) depend on the H+ concentration. The third step is very slow, k(3) = (1.08 +/- 0.03) x 10(-3) s(-1), and does not depend on the H+ concentration. Latter rate-determining step involves an isomerisation process forcing the copper(II) ion to leave rapidly the macrocyclic cavity. The reaction mechanism of the complex dissociation has been proposed, taking into account the results obtained for related systems by independent methods: potentiometry, UV/VIS and EPR spectroscopies, X-ray diffraction analysis, and molecular mechanics calculations