N. I. Pechurova

Reaction of vanadium(V) with hydrazine sulfate in the presence of certain complexones

ConclusionsThe authors have investigated the kinetics of the redox reaction of V(V) with N2H4 · H2SO4 in the presence of complexones of ethylenediaminetetraacetic, diethylenetriaminepentaacetic, and nitrilotriacetic acids; two mechanisms of the redox processes are proposed.

Complexing of cerium(IV) with nitrilotriacetic acid in the presence of sulfate and nitrate ions

The authors have made a spectrophotometric investigation of the composition of the complexes formed in the system Ce(IV)-nitrilotriacetic acid in 1 M (NH4)2SO4 and 1 M NH4NO3 solutions and have calculated the instability constants of CeX+ and CeX 2 2− complexes.

Study of the kinetics of the oxidation of complexones by vanadium (V)

The kinetics of the oxidation of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid by vanadium(V) was studied; the reaction is first order with respect to V(V) and the complexone. The reaction rate constants were determined, and the activation energies of the oxidation processes were calculated.

Investigation of the interaction of compounds of vanadium (V) with complexones

1. The redox interaction of V(V) with diethylenediaminepentaacetic, ethylenediaminetetraacetic, and nitrilotriacetic acids was investigated by a spectrophotometric method. 2. The composition and instability constants of the complexonates of V(V) were determined.

IR-spectroscopic study of diethylenetriaminepentaacetic acid and its potassium salts

1. From the IR spectra of diethylenetriaminepentaacetic acid (H5L) and its potassium salts K3H2L and K5L it follows that H5L and K3H2L have a betaine structure in the solid state, and the dissociated carboxyl groups participate in the formation of hydrogen bonds. 2. K5L is a compound with an ionic K-O bond.

Investigation of the interaction of Ce(IV) with diethylenetriaminepentaacetic acid

The formation of a neutral monocomplex of Ce(IV) with diethylenetriaminepentaacetic acid was found by a spectrophotometric method. The instability constant of the complex at μ=1.0 and pH 1.4, the value of which was equal to (0.8±0.2)·10−34, was calculated.

KINETICS OF ELECTROPHILIC EXCHANGE OF LANTHANIDE(III) AND COPPER(II) IONS IN AQUEOUS SOLUTIONS OF THE ETHYLENEDIAMINETETRAACETATES

Conclusions1.Electrophilic substitution in the systems RE ethylenediaminetetraacetate-copper(II) is brought about by an acidic dissociation mechanism and by an associative mechanism.2.It is suggested that in acidic dissociation the exchange is limited by the rupture of the metal-oxygen bond in the intermediate protonated complex, while in the case of the associative mechanism it is limited by the rupture of the metal-nitrogen bond in the intermediate binuclear complex.3.In the systems studied there are differences between the exchange mechanisms for the RE in the cerium and yttrium subgroups.

Kinetics of the exchange reaction between neodymium (III) transcyclohexanediamine tetraacetate and aquo-ions of europium (III) and holmium (III) in H2O and D2O solutions

Conclusions1.Electrophilic substitution in the systems NdD−−Eu3+, NdD−−Ho3+ (D4− is cyclohexanediamine tetraacetate) is brought about by a dissociative mechanism catalyzed by protons and by a spontaneous dissociation mechanism. The decomposition of an intermediate protonated complex limits exchange by an acid-catalyzed mechanism.2.An associative mechanism for electrophilic exchange is not realized in the systems studied.

Kinetics of electrophilic substitution of erbium(III) by ytterbium(III) in an aqueous solution of ethylenediaminetetraacetate

Conclusions1.Electrophilic substitution in ethylenediaminetetraacetates of rare-earth(III) elements, independently of the nature of the leaving cation, is accomplished according to two competing mechanisms: an acid dissociation mechanism and an associative mechanism.2.Exhange according to the acid dissociation mechanism is catalyzed by protons; and depending on the acidity of the medium, singly and doubly protonated intermediate complexes are formed.3.The associative exchange mechanism predominates in less acid media and is realized by means of formation of intermediate binuclear complexes. The limiting step for exchange according to an associative mechanism is the breaking of the metal-nitrogen bond, formed by the leaving cation and the ligand in the intermediate binuclear complex.

Effect of adduct formation on the valence state of cerium in its β-diketonates

Conclusions1.Physicochemical investigation of the cerium(III, IV)-β-diketone-additional ligand system showed that the capacity ofβ-diketonates for adduct formation decreases in the order thenoyltrifluoroacetonate > acetylacetonate > dibenzoylmethanide > benzoylacetonate.2.Adduct formation in the cerium(III, IV)β-diketonates stabilizes the cerium in the trivalent state, whereas the degree of oxidation of 4+ is stable in the tetrakis-β-diketonates.3.According to the effect on the stabilization of cerium(III) in itsβ -diketonates the additional ligands can be arranged in the following order: tributyl phosphate < trioctylphosphine oxide < triphenylphosphine oxide