Coördination Compounds. II. Trends in the Stability of Some Rare Earth Chelates

Cefola, Michael; Tompa, Albert S.; Celiano, Alfred V.; Gentile, P.S.

doi:10.1021/ic50002a018

Cited by 76 publications

(24 citation statements)

References 2 publications

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“…J. Chem. Downloaded from www.nrcresearchpress.com by 34 Table 2 for pK, for all three acids conform with the relationships just given. With respect to values of pK, the situation is acceptable only for sulfosalicylic acid, but even here the thermodynamic values of Nair (42) (45) can be regarded as established with sufficient precision, yet obviously this cannot be used in conjunction with data secured in solutions of lower ionic strength.…”

Section: Resultssupporting

confidence: 78%

Stability constants of three iron(III) salicylates

Rohr¹,

Penciner²,

Page³

1970

Can. J. Chem.

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Stability constants of the iron(II1) compIexes of salicylic acid, sulfosalicylic acid, and 4-aminosalicyIic acid, together with several of the acidity constants of these, have been determined at 25 "C and in solutions with 0.5 M background electrolyte. For the spectrophotometric measurement of the stability constants improved methods for determining the extinction coefficients of the first and second complexes are described. Protonated species appear only with the aminosalicylate complexes, and the site of this protonation is discussed. Previous values of these equilibrium constants have been collected and critically assessed.Canadian Journal o f Chemistry, 48, 2574Chemistry, 48, (1970 Introduction A spectrophotometric procedure for the estimation offormation constants of metal complexes initially suggested by Vareille (1) has been extended (2, 3), particularly by increasing the number of inde~endent estimates that could be extracted from measurements on a suitable group of solutions. In this paper are communicated some additional refinements to the experimental procedure and to the treatment of the experimental data, together with the results of studies on complexes formed by iron(II1) with salicylates.These particular complexes were selected for study for several reasons. The substantially different magnitudes of the successive stability constants make it possible to study spectrophotometrically the individual steps in the formation of these complexes. One of the advantages of the procedure is its ability to test the dependence of the measured values of formation constants on hydrogen-ion concentration. Thus the method had been used (3) to confirm the formation of a protonated complex MHL in the reaction between iron(II1) and Tiron (disulfonated catechol) (4). It was of interest to see whether, under comparable conditions of low pH, a similar reaction occurred with sulfosalicvlic acid. The iron(II1) complexes of this reagent have already been investigated by several workers (5-lo), and apart from some early observations ( 9 , no 'This work was begun in the Department of Chemistry, University of Toronto, and completed and prepared for publication in the Department of Medical Chemistry, Australian National University, Canberra. 2Present address: Department of Chemistry, Tel-Aviv University, Tel-Aviv, Tsrael. 3Present address: Department of Chemistry, Queen's University, Kingston, Ontario. dependence of the formation constants on the acidity of the solution had been reported. However, the experimental methods or conditions applying to these previous investigations may not have been chosen with the objective of proving or disproving the formation of a protonated species. Mattoo (7) specifically commented on the absence of a protonated 1 :I complex when subjecting Vareille's experimental results to his own method of calculation. Salicylic acid and some other salicylates have been reported in one study to form protonated iron(II1) complexes (1 l), though other workers (9, 10, 12-14) have not reported on such a ...

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Section: Resultssupporting

confidence: 78%

Stability constants of three iron(III) salicylates

Rohr¹,

Penciner²,

Page³

1970

Can. J. Chem.

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“…Rare-earth glycolate complexes have been reported by numerous authors (18,19,26,27,28,29,30). The glycolate ligand is bidentate and apparently forms 1:1, 2:1, 3=1 and i+:l complexes with the rare earths.…”

Section: Review Of Literature On Rare-earth Complexesmentioning

confidence: 95%

“…The glycolate ligand is bidentate and apparently forms 1:1, 2:1, 3=1 and i+:l complexes with the rare earths. The glycinate anion has been found to form stronger complexes with lanthanim, cerixim, praseodymium and neodymium than does glycolate (26).…”

Section: Review Of Literature On Rare-earth Complexesmentioning

confidence: 97%

“…Thioglycolate and methoxyacetate complexes have been reported which are weaker than corresponding acetate complexes (26,31). Apparently the sulfhydryl and methoxy groups contribute little or nothing to complex formation.…”

Section: Review Of Literature On Rare-earth Complexesmentioning

confidence: 99%

“…The lactate complexes are stronger than the corresponding glycolates. The lanthanum, cerium, praseodymium and neodymium complexes of j3-alaninate, p-hydroxypropionate, and p-mercaptopropionate decrease in stability in the order of the ligands listed (26). The a-hydroxyisobutyrate complexes have been studied also and were found to be stronger than the corresponding lactate and glycolate species (27,29).…”

Section: Review Of Literature On Rare-earth Complexesmentioning

confidence: 99%

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Formation Constants of Some Rare-Earth Complexes

Stagg¹,

Powell²

1963

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The Hydrogen Salicylate Ion as Ligand. Complex Formation Equilibria with Dioxouranium(VI), Neodymium(III) and Lead(II)

Furia

Porto

2004

Annali di Chimica

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The complexation equilibria of the hydrogen salicylate ion, HL‐, have been studied, at 25 °C, by potentiometric measurements with a glass electrode in 1 M NaClO4 for uranyl and Nd(III) ions and in 3 M NaClO4 for Pb(II) ion. The ligand concentration (CL) was varied between 10‐3 and 0.05 M. In the system with U(VI) the concentrations ranged between: 10‐3 ≤ [U(VI)] ≤ 0.01 M, 0.5 ≤ CL /[U(VI)] ≤ 10 and 10‐2 d[H+]≤ 10‐5 M; for neodymium system: 2.10‐3 ≤ [Nd(III)] < 0.01, 1 ≤ CL /[Nd(III)] ≤ 10 and 10‐2 ≤ [H+] ≤ 10‐7 M; for lead system: 10‐3 ≤ [Pb(II)] ≤ 3.10‐3, 1 ≤ CL /[Pb(II)] ≤ 2 and 10‐5 ≤ [H+] ≤ 10‐7.3 M. The experimental data have been explained with the formation of UO2HL+, UO2L, UO2(OH)L , (UO2)2(OH)L2 UO2(HL)L , NdHL2+, NdL+, Nd(OH)L, PbHL+, PbL and PbL22—. Equilibrium infinite dilution.

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Coördination Compounds. II. Trends in the Stability of Some Rare Earth Chelates

Cited by 76 publications

References 2 publications

Stability constants of three iron(III) salicylates

Stability constants of three iron(III) salicylates

Formation Constants of Some Rare-Earth Complexes

The Hydrogen Salicylate Ion as Ligand. Complex Formation Equilibria with Dioxouranium(VI), Neodymium(III) and Lead(II)

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