Complexation of copper(II) with nitrilotriacetic acid in aqueous and water-acetonitrile solutions at variable concentrations of supporting electrolyte

The pH-metric titration was used to determine dissociation constants of nitrilotriacetic acid (H3L) and to study its complexation with copper(II) in aqueous and water-acetonitrile solutions (t = 25 ± 0.05°C) at variable concentrations of a supporting electrolyte (μ = 0.5-3.0, NaClO4, NaNO3). The dissociation constants of H3L increase as the content of the supporting salt in an aqueous solution increases. The composition of the copper(II) nitrilotriacetate complexes in the presence of NaClO4 and NaNO3 is more complicated than in the presence of KNO3. A tendency of the carboxyl groups of H3L toward dissociation decreases and the stability of the similar copper(II) complexes increases in aqueous acetonitrile (Xs = 0.19 mole fractions) compared to those in an aqueous solution. © 1997 MAEe cyrillic signK Hayκa/Interperiodica Publishing

Volume properties of the hydrolyzed aluminum species

The composition of polynuclear aluminum hydroxo complexes, their hydrolysis constants, and the volume changes due to complex formation have been determined by CPESSP software analysis of the potentiometry and dilatometry data. © 2013 Pleiades Publishing, Ltd

Thiocyanatomolybdenum(V) Complexes

Formation of thiocyanatomolybdenum(V) complex ions [MoO(NCS)2]+, H3[MoOCl3(NCS)2]+, H4[MoOCl4(NCS)]2+, H4[MoOCl5]2+, H4[MoOCl3(NCS)]3+, and H2[MoOCl2]3+ (within the range of 0.7-5 mol/l HCl) and H4[MoOBr3(NCS)2]2+ and H4[MoOBr5]2+ (for 5 mol/l HBr) in aqueous solution was shown by means of spectrophotometry and mathematical simulation. As compared to bromide ions, Cl- ions demonstrate a higher competitive ability when thiocyanato ions occur in the coordination sphere of molybdenum(V). The absence of polymeric complex species confirms the depolymerizing properties of the ligand under investigation

Complexation between copper(II) and ethylenediaminetetraacetic acid in aqueous acetonitrile

The complexation between copper(II) and ethylenediaminetetraacetic acid (H4L) in an aqueous solution of acetonitrile (XCH3CN=0.34 molar fractions) is studied by spectrophotometry. The formation of ethylenediaminetetraacetates [CuHL]- and [CuL]2- is established. No [CuH2L] complexes are observed. It is shown that the addition of acetonitrile makes the HL3- and L4- anions dentate higher. The coordination number of the Cu2+ ion in the [CuHL]- complex decreases in the presence of CH3CN and NaClO4 (1.5 mol/1). DMSO (X = 0.36 molar fractions) and DMF (X = 0.33 molar fractions) molecules are outerspherically bound by copper(II) ethylenediaminetetraacetate complexes. © 1996 MAEe Cyrillic signK Hayκa/Interperiodica Publishing

Solubility products of basic salts Cu2(OH)3NO 3 and Hg3O2(NO3)2, determined from dilatometric data

The solubility products of basic salts Cu2(OH) 3NO3 and Hg3O2(NO3) 2 were determined using dilatometric data. © 2008 MAIK Nauka

Dissociation of ethylenediaminetetraacetic acid and stability of copper(II) ethylenediaminetetraacetates in aqueous solutions of ammonium nitrate

The dissociation constants (K1 and K2) of the carboxy groups of ethylenediaminetetraacetic acid (H4L) and the dissociation constant (K5) of the protonated form H5L+ were determined by pH-metric titration in the pH range 1.3-4.5 at variable concentrations of ammonium nitrate (μ = 1.0-7.0) in an aqueous solution (I = 25 ± 0.05°C). The dissociation constants of the ammonium groups in H4L (K3 and K4) failed to be determined under the experimental conditions chosen. For KNO3 and NaClO4 (μ = 1.2), all K1-K5 constants were calculated. The complexation of H4L with copper(II) in the presence of the supporting electrolytes of the indicated concentrations was studied by spectrophotometry and pH-metric titration. In the strongly acidic region, the [CuH3L]+ species was found to form, in addition to the diprotonated and monoprotonated copper(II) complexonates. The equilibrium constants for the formation of the complexonates change nonmonotonically with increase in the concentration of ammonium nitrate. At comparable ionic strengths of the solutions created by KNO3 (μ = 1.2), NH4NO3 (μ = 1.0), and NaClO4 (μ = 1.2), the effect of NaClO4 is most pronounced: the equilibrium constants decrease by ∼2 units of logK for all the complexonates. The formation of the heteroligand complex [CuLNH3]2- in the aqueous solutions of ammonium nitrate (pH > 6) was established by the spectrophotometric method. © 1998 MAEe cyrillic signK Hayκa/Interperiodica Publishing

Complexation of copper(II) with ethylenediamine in an aqueous dioxane solvent

The spectrophotometric and pH-metric methods are used to study the complexation of copper(II) with ethylenediamine in aqueous dioxane (Xs = 0.17-0.48 mole fraction) solvent in the presence of NaClO4 (μ = 0.1 and 0.5). Starting from Xs = 0.17 mole fraction, the growth in the stability of the [CuEn]2+ and [CuEn2]2+ complexes becomes inconsistent with the dissolution factor because of the solvation processes in the system under consideration. Dioxane forms the solvate complexes with copper(II) through the inner-sphere coordination to the mono(ethylenediamine)copper(II) complex. In the bis(ethylenediamine)copper(II) complex, either the outer-sphere or simultaneous outer- and inner-sphere coordination of dioxane are most probable. © 1996 MAEe cyrillic signK Hayκa/Interperiodica Publishing

Selective solvation of cations and proton donors in the water-dipolar aprotic solvent mixtures

Selective solvation of rare-earth (yttrium subgroup), cobalt(II), nickel(II), and copper(II) ions and proton donors [L-(+)-tartaric acid and its dianion; protonated, zwitterionic, and anionic forms of L-α-alanine and L-β-phenyl-α-alanine] in binary water-dipolar aprotic solvent (acetonitrile, dimethyl sulfoxide, dimethyl-formamide, and hexamethylphosphoramide) mixtures of variable composition is examined. The relationships X′2 = f(X2 0), where X′2 and X2 0 are the mole fractions of the dipolar aprotic solvent (DAS) in the nearest surroundings of the solvated species and in the bulk, respectively, show that, on the background of the preferential solvation by the DAS molecules, there are some cases of inversion of solvation selectivity. This fact is explained in terms of the steric and dipole-dipole intermolecular interactions. © 1998 MAEe cyrillic signK Hayκa/Interperiodica Publishing