Complex Formation Between Zinc(II) and Alkyl-N-iminodiacetic Acids in Aqueous Solution and Solid State

Abstract Removal of metal compounds from wastewater using processes where metals can be removed and valuable chemicals recycled is of significant industrial importance. Chelating surfactants are an interesting group of chemicals to be used in such applications. Carboxylated polyamines are a promising group to be used in such processes. To apply carboxylated polyamines as chelating surfactants, detailed knowledge of the solution chemistry, including complex formation, kinetics and structures of pure fundamental systems, is required. In this study zinc(II) alkyl-N-iminodiacetate systems with varying length of the alkyl chain have been studied. Acidic and stability constants have been studied by potentiometry, and the structures of both solids and aqueous solutions have been determined by EXAFS. Zinc(II) forms two strong complexes with alkyl-N-iminodiacetates in aqueous solution. In an attempt to determine the acidic constants of these complexes, the deprotonation of the nitrogen atom in the complex bound ligands, it was observed that this reaction is very slow and no accurate values could be obtained. The bis(alkyl-N-iminodiacetato)zincate(II) complexes take, however, up two protons in the pH region 3–7, which means that this complex is approximately singly protonated in the pH region 3–7 and doubly protonated at pH < 3. The bis(n-hexyl-N-iminodiacetato)zincate(II) complex at pH = 13 has a distorted octahedral configuration with four short strong Zn–O bonds at 2.08(1) Å, while the Zn–N bonds are weaker at much longer distance, 2.28(2) Å. Similar configurations are also found in most reported structures of zinc(II) complexes with carboxylated amines/polyamines. The singly protonated complex seems to be five-coordinate, with four Zn–O bond distances at ca. 2.03 Å, and a single Zn–N bond distance in the range 2.15–2.25 Å. The relationship between the structure of the protonated bis(n-hexyl-N-iminodiacetato)zincate(II) complex and the slow kinetics in the region pH = 3–7 are discussed.

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Complex Formation of Alkyl-N-iminodiacetic Acids and Hard Metal Ions in Aqueous Solution and Solid State

Journal of Solution Chemistry ◽

10.1007/s10953-020-01025-8 ◽

2020 ◽

Vol 49 (9-10) ◽

pp. 1250-1266

Author(s):

Cecilia Lindblad ◽

Anders Cassel ◽

Ingmar Persson

Keyword(s):

Aqueous Solution ◽

Solid State ◽

Bond Distance ◽

Degree Of Hydrolysis ◽

Acid Base ◽

Strong Base ◽

Slow Kinetics ◽

The Mean ◽

Low Solubility ◽

Base Properties

Abstract The calcium(II), iron(III) and chromium(III) alkyl-N-iminodiacetate systems have been studied in aqueous solution with respect to stability, acid–base properties and structure. The calcium(II) ion forms only one weak complex with methyl-N-iminodiacetic acid in water, K1 = 12.9 (2) mol–1⋅dm3, while iron(III) and chromium(III) form very stable complexes with alkyl-N-iminodiacetic acids. The calcium(II)–methyl-N-iminodiacetate complex is octahedral in the solid state with most probably water in the remaining positions giving a mean Ca–O bond distance of ca. 2.36 Å. The iron(III) alkyl-N-iminodiacetate complexes have low solubility due to a strong tendency to form polymeric structures. Depending on pH in the solution at their preparation, the degree of hydrolysis in the resulting compound(s) may differ. In the solid state, the polymeric iron(III) alkyl-N-iminodiacetate compounds seem to have the mean composition Fe2O(Cx-IDA)5; the mean Fe–O bond distances to the oxo group and the alkyl-N-iminodiacetate ligands are 1.92 and 2.02 Å, respectively. In these complexes the nitrogen atoms are bound at much longer bond distances, 0.1–0.2 Å, than the carboxylate oxygens. This distribution with short strong Fe–O bonds and much longer and weaker Fe–N bonds is also found in most other structurally characterized iron(III) carboxylated amine/polyamine complexes. The chromium(III) alkyl-N-iminodiacetate complexes are octahedral in both solution and solid state, and the low solubility of the solid compounds indicates a polymeric structure with the ligands bridging chromium(III) ions. Also, chromium(III) binds oxygen atoms in carboxylated amines at significantly shorter distance than the nitrogen stoms. The chromium(III) alkyl-N-iminodiacetate complexes display such slow kinetics at titration with strong base that the back-titration with strong acid shows completely different acid–base properties, thus the acid–base reactions are irreversible.

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ChemInform Abstract: THERMODYNAMICS OF METAL COMPLEX FORMATION IN AQUEOUS SOLUTION. XIII. ENTHALPY Y MEASUREMENTS ON COPPER(I) AND SILVER(I) HALIDE SYSTEMS

Chemischer Informationsdienst ◽

10.1002/chin.197808019 ◽

1978 ◽

Vol 9 (8) ◽

Author(s):

S. AHRLAND ◽

B. TAGESSON ◽

D. TUHTAR

Keyword(s):

Aqueous Solution ◽

Complex Formation ◽

Metal Complex

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Schiff base equilibria. II. Beryllium complexes of N-n-butylsalicylideneimine and the hydrolysis of the Be2+ ion

Australian Journal of Chemistry ◽

10.1071/ch9650651 ◽

1965 ◽

Vol 18 (5) ◽

pp. 651 ◽

Cited By ~ 12

Author(s):

RW Green ◽

PW Alexander

Keyword(s):

Aqueous Solution ◽

Schiff Base ◽

Complex Formation ◽

Distribution Coefficient ◽

Dilute Aqueous Solution ◽

The Stability ◽

Ph Range ◽

Hydrolysis Of ◽

Beryllium Complexes ◽

Equilibria In Aqueous Solution

The Schiff base, N-n-butylsalicylideneimine, extracts more than 99.8% beryllium into toluene from dilute aqueous solution. The distribution of beryllium has been studied in the pH range 5-13 and is discussed in terms of the several complex equilibria in aqueous solution. The stability constants of the complexes formed between beryllium and the Schiff base are log β1 11.1 and log β2 20.4, and the distribution coefficient of the bis complex is 550. Over most of the pH range, hydrolysis of the Be2+ ion competes with complex formation and provides a means of measuring the hydrolysis constants. They are for the reactions: Be(H2O)42+ ↔ 2H+ + Be(H2O)2(OH)2, log*β2 - 13.65; Be(H2O)42+ ↔ 3H+ + Be(H2O)(OH)3-, log*β3 -24.11.

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Comparison of a Non Electrostatic Surface Complexation Model and Surface Phase Theories for Prediction of Future Sorption Properties.

MRS Proceedings ◽

10.1557/proc-824-cc7.2 ◽

2004 ◽

Vol 824 ◽

Author(s):

Allan T. Emrén ◽

Anna-Maria Jacobsson

Keyword(s):

Aqueous Solution ◽

Chemical Potential ◽

Surface Complexation ◽

Sorption Properties ◽

Phase Method ◽

Detailed Knowledge ◽

Surface Phase ◽

Surface Complexation Model ◽

Advantages And Disadvantages ◽

The One

AbstractIn performance assessments, sorption of radionuclides dissolved in groundwater is mostly handled by the use of fixed Kd values. It has been well known that this approach is unsatisfying. Only during the last few years, however, tools have become available that make it possible to predict the actual Kd value in an aqueous solution that differs from the one in which the sorption properties were measured.One such approach is surface complexation (SC) that gives a detailed knowledge of the sorption properties. In SC, one tries to find what kinds of sorbed species are available on the surface and the thermodynamics for their formation from species in the bulk aqueous solution. Recently, a different approach, surface phase method (SP), has been developed. In SP, a thin layer including the surface is treated as a separate phase. In the bulk aqueous solution, the surface phase is treated as a virtual component, and from the chemical potential of this component, the sorption properties can be found.In the paper, we compare advantages and disadvantages of the two kinds of models. We also investigate the differences in predicted sorption properties of a number of radionuclides (Co, Np, Th and U). Furthermore, we discuss under which circumstances, one approach or the other is preferable.

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