Palladium(II) diamine complex induces reduction of glutathione disulfide

Reaction of [Pd(1R,2R-diaminocyclohexane)Cl(2)] with the oxidised form of the tripeptide glutathione ([gamma]-l-glutamyl-l-cysteinyl-glycine) in aqueous solution leads to reductive cleavage of the disulfide bond.     

Reaction of Gelatin-immobilized Lead(II) Hexacyanoferrate(II) with Dithioxamide

Russian Journal of General Chemistry -     

Lead(II) Siloxides

Although Pb^II-siloxides have been known until now to decompose to oxoclusters, here [{RO^F}PbOSi(SiMe₃)₃] (RO^F=fluoroalkoxide) and, most importantly, [Pb₂{OSi(SiMe₃)₃}{μ₂-OSi(SiMe₃)₃}₃], are presented. The unusual bonding pattern in the latter thermally stable dinuclear complex was investigated by crystallographic and computational methods. Its stability is much higher than that of the simple, yet elusive “[Pb(OSiPh₃)₂]”, for which decomposition pathways towards [Pb₄(μ₄-O)(μ₂-OSiPh₃)₆] have been clearly established.     

Studies in the complex formation of metal ions with sugars. I. The complex formation of cobalt(II), cobalt(3), copper(II) and nickel(II) with mannitol

The use of elastic polyurethane foam as a support for chloranil was proved successful. Reductions of cerium(IV), vanadium(V) and iron(II) on foam-filled columns were carried out quantitatively and rapidly. The effect of flow-rate and temperature on the reduction of each metal ion was examined in detail. Cerium(IV) was reduced quantitatively on passing through the foam-redox column at flow-rates of 2–11 ml min^-1 at room temperature. The reduction of vanadium(V) and iron(III) was slower; complete reduction occurred only at flow-rates up to 4 and 2 ml min^-1 for V(V) and Fe(III), respectively. At 35°, however, it was possible to use flow-rates of 7 and 6 ml min^-1 for the quantitative reduction of V(V) and Fe(III), respectively.     

Cadmium(II) N-acetylcysteine complex formation in aqueous solution

The complex formation between Cd(II) ions and N-acetylcysteine (H(2)NAC) in aqueous solution was investigated using Cd K- and L(3)-edge X-ray absorption and (113)Cd NMR spectroscopic techniques. Two series of 0.1 M Cd(II) solutions with the total N-acetylcysteine concentration c(H2NAC) varied between 0.2-2 M were studied at pH 7.5 and 11.0, respectively. At pH = 11 a novel mononuclear [Cd(NAC)(4)](6-) complex with the average Cd-S distance 2.53(2) ? and the chemical shift δ((113)Cd) = 677 ppm was found to dominate at a concentration of the free deprotonated ligand [NAC(2-)] > 0.1 M, consistent with our previous reports on cadmium tetrathiolate complex formation with cysteine and glutathione. At pH 7.5 much higher ligand excess ([HNAC(-)] > 0.6 M) is required to make this tetrathiolate complex the major species. The (113)Cd NMR spectrum of a solution containing c(Cd(II)) = 0.5 M and c(H2NAC) = 1.0 M measured at 288 K showed three broad signals at 421, 583 and 642 ppm, which can be attributed to CdS(3)O(3), CdS(3)O and CdS(4) coordination sites, respectively, in oligomeric Cd(II)-NAC species with single thiolate bridges between the cadmium ions.     

Acid-base properties of bis(hydrazinocarbonylmethyl) sulfoxide and its complex formation with copper(II) and nickel(II)

Behavior of physiologically active compound, bis(hydrazinocarbonylmethyl) sulfoxide, in aqueous solution has been studied by means of potentiometry, spectrophotometry, and mathematical simulation. Protolytic properties of bis(hydrazinocarbonylmethyl) sulfoxide have been described, and the formation of sodium salt has been confirmed. Composition and stability constants of bis(hydrazinocarbonylmethyl) sulfoxide complexes with copper(II) and nickel(II) have been determined, and the complexes structures have been simulated by molecular mechanics method.     

Potentiometric study of complex formation equilibria of alpha-oxooximes with copper(II) and nickel(II) and ions

Complex formation equilibria between copper(II) and nickel(II) with phenylglyoxal 2-oxime (HPGO) and 1-phenyl-1,2-propanedione 2-oxime (HPPO) have been studied in 50% (v/v) ethanol-water solution containing 0.5M sodium nitrate as constant ionic medium at 25 degrees , using glass electrode potentiometry. The emf data obtained have been analysed with MINIGLASS and SUPERQUAD programs. Formation constants for the Cu(PGO)(+), Cu(2)(PGO)(OH)(2+), Cu(2)(PGO)(2)(OH)(+), Ni(PGO)(+), Ni(2)(PGO)(3)(+), Ni(2)(PGO)(4), Ni(2)(PGO)(2)(OH)(2), Cu(2)(PPO)(OH)(+) and Cu(2)(PPO)(2)(OH)(+) complexes are reported.     

Mixed complex formation of lead(II) and mercury(II) ethylenediaminetetraacetates with thiourea in an aqueous solution

The formation of mixed-ligand complexes HgEdtaThio²⁻, HgEdtaS₂O₃⁴⁻, PbEdtaThio²⁻, and Pb(Thio) _i ²⁺, i = 1, 2; Thio is thiourea) was studied by calorimetry, pH metry, and ¹H and ¹³C NMR spectroscopy. The thermodynamic parameters (logK, Δ _r G ⁰, Δ _r H, and Δ _r S) for the formation of the complexes at 298.15 K and the ionic strength I = 0.5(NaClO₄) were determined. The most probable coordination mode of the ligands in the mixed complex was considered.     

Lead (II) cholate solubility

In the framework of the research carried out on the behaviour of the salts of bile acids in aqueous solutions, the lead (II) cholate solubility was determined at 25 degrees C and in 0.100, 0.500 and 0.800 mol dm(-3) N(CH3)4Cl, as ionic medium. The change of its solubility was studied as a function of the cholate and hydrogen ion concentration. Solubility and electromotive force measurements of suitable galvanic cells were carried out and from the results lead (II) cholate solubility product could be calculated and the presence of associated species in solution in the ratio 1:3 and 1:4 between lead (II) and cholate was assumed. The relative constants were determined, as well. The results of this work allow us to obtain the free cholate concentration in equilibrium with solid lead (II) cholate.     

Mercury(II) penicillamine complex formation in alkaline aqueous solution

The complex formation between mercury(II) and penicillamine (H(2)Pen = 3,3'-dimethyl cysteine) in alkaline aqueous solutions (pH approximately 2) has been investigated with extended X-ray absorption fine structure (EXAFS) and 199Hg NMR spectroscopy. By varying the penicillamine concentration (C(H(2)Pen) = 0.2-1.25 M) in approximately 0.1 M Hg(II) solutions, two coexisting major species [Hg(Pen)2](2-) and [Hg(Pen)3](4-) were characterized with mean Hg-S bond distances 2.34(2) and 2.44(2) A, respectively. The [Hg(Pen)2](2-) complex with two deprotonated penicillamine ligands forms an almost linear S-Hg-S entity with two weak chelating Hg-N interactions at the mean Hg-N distance 2.52(2) A. The same type of coordination is also found for the corresponding [Hg(Cys)2](2-) complex in alkaline aqueous solution with the mean bond distances Hg-S 2.34(2) A and Hg-N 2.56(2) A. The relative amounts of the [Hg(Pen)2](2-) and [Hg(Pen)3](4-) complexes were estimated by fitting linear combinations of the EXAFS oscillations to the experimental spectra. Also their (199)Hg NMR chemical shifts were used to evaluate the complex formation, showing that the [Hg(Pen)3](4-) complex dominates already at moderate excess of the free ligand ([Pen(2-)] > approximately 0.1 M).     

Potentiometric investigation of complex formation of lead(II) with glycine and dl-alanine

The complex formation of lead(II) with glycine and dl-alanine was investigated at 25°C in 3 mol dm⁻³ NaClO₄ medium by e.m.f. titrations using glass and amalgam electrodes. The e.m.f. measurements were performed in the −log[H⁺] range between 2.5 and 9. Analysis of the e.m.f. data revealed that PbHL²⁺ is formed at −log[H⁺]<5 and PbL⁺ and PbL₂ at higher −log[H⁺] values in both glycine and dl-alanine systems. The protonation constants of glycine and dl-alanine and the formation constants of the complexes are tabulated in Tables 1 and 2.     

Study of complex formation between lead(II) acetate andmeso-tetraphenylporphin

The reaction of Pb(OAc)₂ withmeso-tetraphenylporphin in boiling pyridine orN,N-dimethylformamide gave complexes of Pb^II with tetraphenylchlorin or Pb^IV with tetraphenylporphin. The scheme of redox reactions occurring during the complex formation involving Pb²⁺ as the reducing agent was suggested. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2052–2055, October, 1998.     

Reactions of Tin and Lead with Tricarbonylcyclopentadienylmolybdenum(II) and Tricarbonylcyclopentadienyltungsten(II) Chlorides

Tin was oxidized with tricarbonylcyclopentadienylmolybdenum and tricarbonylcyclopentadienyltungsten chlorides to obtain polynuclear organometallic compounds [⁵-C₅H₅M(CO)₃]₂SnCl₂ (M = Mo, W). The reactions of the above-mentioned oxidants with lead gave lead chloride and [⁵-C₅H₅M(CO)₃]₂ dimers. Formal-kinetic regularities of tin oxidation with tricarbonylcyclopentadienylmolybdenum chloride in N,N-dimethylformamide were found. Thermodynamic parameters of adsorption of the reagent on the metal surface were determined.