The stabilities and thermodynamic functions for the formation of aluminium and mercury (II) chelates of certain polyaminepolyacetic acids

Moeller, Therald; Chu, Shu‐Kung

doi:10.1016/0022-1902(66)80238-5

Cited by 21 publications

(3 citation statements)

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“…40 Doi tried to verify the correctness of his value by a comparison of his ΔS°for Fe III edta with that of Al III edta. 48,49 This comparison cannot be considered reasonable because there is a large difference between the ionic radii of Al III (0.535 A ˚) and Fe III (0.645 A ˚), 50 leading to the expected higher ΔS°values for the formation of aluminum(III) complexes as compared to those of iron(III) complexes. We consider our data for Fe III edta to be more reliable based on the following arguments.…”

Section: Resultsmentioning

confidence: 99%

“…A large discrepancy is apparent upon comparison of our Δ H ° value for the complex formation of Fe III edta with the value reported by Doi . Doi tried to verify the correctness of his value by a comparison of his Δ S ° for Fe III edta with that of Al III edta. , This comparison cannot be considered reasonable because there is a large difference between the ionic radii of Al III (0.535 Å) and Fe III (0.645 Å), leading to the expected higher Δ S ° values for the formation of aluminum(III) complexes as compared to those of iron(III) complexes.…”

Section: Resultsmentioning

confidence: 99%

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Detailed Spectroscopic, Thermodynamic, and Kinetic Studies on the Protolytic Equilibria of Fe^IIIcydta and the Activation of Hydrogen Peroxide

et al. 2009

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The crystal structure of the as-yet-unknown salt K[Fe(III)(cydta)(H(2)O)].3H(2)O, where cydta = (+/-)-trans-1,2-cyclohexanediaminetetraacetate, has been resolved: orthorhombic space group Pbca with R1 = 0.0309, wR2 = 0.0700, and GOF = 0.99. There are two independent [Fe(III)(cydta)(H(2)O)](-) anions in the asymmetric unit, and the ligand is (R,R)-cydta in both cases. The coordination polyhedron is a seven-coordinate capped trigonal prism where the quadrilateral face formed by the four ligand donor oxygen atoms is capped by the coordinated water molecule. The speciation of [Fe(III)(cydta)(H(2)O)](-) in water was studied in detail by a combination of techniques: (i) Measurements of the pH dependence of the Fe(III/II)cydta redox potentials by cyclic voltammetry enabled the estimation of the stability constants (0.1 M KNO(3), 25 degrees C) of [Fe(III)(cydta)(H(2)O)](-) (log beta(III)(110) = 29.05 +/- 0.01) and [Fe(II)(cydta)(H(2)O)](2-) (log beta(II)(110) = 17.96 +/- 0.01) as well as pK(III)(a1OH) = 9.57 and pK(II)(a1H) = 2.69. The formation enthalpy of [Fe(III)(cydta)(H(2)O)](-) (DeltaH degrees = -23 +/- 1 kJ mol(-1)) was measured by direct calorimetry and is compared to the corresponding value for [Fe(III)(edta)(H(2)O)](-) (DeltaH degrees = -31 +/- 1 kJ mol(-1)). (ii) pH-dependent spectrophotometric titrations of Fe(III)cydta lead to pK(III)(a1OH) = 9.54 +/- 0.01 for deprotonation of the coordinated water and a dimerization constant of log K(d) = 1.07. These data are compared with those of Fe(III)pdta (pdta = 1,2-propanediaminetetraacetate; pK(III)(a1OH) = 7.70 +/- 0.01, log K(d) = 2.28) and Fe(III)edta (pK(III)(a1OH) = 7.52 +/- 0.01, log K(d) = 2.64). Temperature- and pressure-dependent (17)O NMR measurements lead to the following kinetic parameters for the water-exchange reaction at [Fe(III)(cydta)(H(2)O)](-) (at 298 K): k(ex) = (1.7 +/- 0.2) x 10(7) s(-1), DeltaH(++) = 40.2 +/- 1.3 kJ mol(-1), DeltaS(++) = +28.4 +/- 4.7 J mol(-1) K(-1), and DeltaV(++) = +2.3 +/- 0.1 cm(3) mol(-1). A detailed kinetic study of the effect of the buffer, temperature, and pressure on the reaction of hydrogen peroxide with [Fe(III)(cydta)(H(2)O)](-) was performed using stopped-flow techniques. The reaction was found to consist of two steps and resulted in the formation of a purple Fe(III) side-on-bound peroxo complex [Fe(III)(cydta)(eta(2)-O(2))](3-). The peroxo complex and its degradation products were characterized using Mossbauer spectroscopy. Formation of the purple peroxo complex is only observable above a pH of 9.5. Both reaction steps are affected by specific and general acid catalysis. Two different buffer systems were used to clarify the role of general acid catalysis in these reactions. Mechanistic descriptions and a comparison between the edta and cydta systems are presented. The first reaction step reveals an element of reversibility, which is evident over the whole studied pH range. The positive volume of activation for the forward reaction and the positive entropy of activation for the backward reaction suggest a dissoci...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Detailed Spectroscopic, Thermodynamic, and Kinetic Studies on the Protolytic Equilibria of Fe^IIIcydta and the Activation of Hydrogen Peroxide

et al. 2009

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“…Whenever possible the Aml's as expressed in eq 6 were calculated directly from the potentiometric titration data of the 1:1 metal-ligand systems. The titration curves are shown in HEDTA 17.2b (4) UEDDA 16.75 (5) DGENTA 13.26 (4) 9.70 (4) IDA 12.76 (4) HIDA 11.33 (3) DTMA 4.51 (2) CA 10.02 (2)…”

Section: Resultsmentioning

confidence: 99%

Aqueous complexes of gallium(III)

Harris¹,

Martell²

1976

Inorg. Chem.

114

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Complexes of aluminium with aminopolycarboxylic acids: ²⁷Al NMR and potentiometric studies

Iyer

Karweer

Jain

1989

Magnetic Reson in Chemistry

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The reactions of A13+ ion with a series of aminopolycarboxylic acids containing coordinating sites (denticity, n) ranging from 3 to 8 were studied by potentiometric and "A1 NMR methods. Hydrolysis constants of the complexes were determined by potentiometry. The 27Al {'H} NMR data indicate a nearly linear relationship between the 27Al chemical shift of the normal complex and denticity of the ligand up to n = 6. Hydroxo complexes form in all systems, and at high pH (ca. 10) aluminate forms. Protonated complexes were formed in some cases. Diprotonated complexes of EDTA and PDTA have been identified by "A1 NMR spectroscopy. Maximum deshielding of the 27Al resonance was observed for the octahedral [Al(EDTA)I-complex. The Al-NTA complex appears to be the most symmetric of the complexes.

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The stabilities and thermodynamic functions for the formation of aluminium and mercury (II) chelates of certain polyaminepolyacetic acids

Cited by 21 publications

References 25 publications

Detailed Spectroscopic, Thermodynamic, and Kinetic Studies on the Protolytic Equilibria of Fe^IIIcydta and the Activation of Hydrogen Peroxide

Detailed Spectroscopic, Thermodynamic, and Kinetic Studies on the Protolytic Equilibria of Fe^IIIcydta and the Activation of Hydrogen Peroxide

Aqueous complexes of gallium(III)

Complexes of aluminium with aminopolycarboxylic acids: ²⁷Al NMR and potentiometric studies

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The stabilities and thermodynamic functions for the formation of aluminium and mercury (II) chelates of certain polyaminepolyacetic acids

Cited by 21 publications

References 25 publications

Detailed Spectroscopic, Thermodynamic, and Kinetic Studies on the Protolytic Equilibria of FeIIIcydta and the Activation of Hydrogen Peroxide

Detailed Spectroscopic, Thermodynamic, and Kinetic Studies on the Protolytic Equilibria of FeIIIcydta and the Activation of Hydrogen Peroxide

Aqueous complexes of gallium(III)

Complexes of aluminium with aminopolycarboxylic acids: 27Al NMR and potentiometric studies

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Detailed Spectroscopic, Thermodynamic, and Kinetic Studies on the Protolytic Equilibria of Fe^IIIcydta and the Activation of Hydrogen Peroxide

Detailed Spectroscopic, Thermodynamic, and Kinetic Studies on the Protolytic Equilibria of Fe^IIIcydta and the Activation of Hydrogen Peroxide

Complexes of aluminium with aminopolycarboxylic acids: ²⁷Al NMR and potentiometric studies