Complexation of the Aqua-Iron(III) Dimer by Tiron: Kinetics of Complex Formation and Dissociation

Chatłas, Janusz; Jordan, R. B.

doi:10.1021/ic00095a027

Cited by 14 publications

(18 citation statements)

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“…Similar combination can be used to obtain the Δ H * and Δ S * for k 1 and k 1 ‘ given in Table . The value of K f1 is in good agreement with that of 1.8 M determined by McBryde, and k 1 ‘ agrees with the values of 2.1 × 10 3 and 2.2 × 10 3 M -1 s -1 determined from formation kinetics by Mentasti et al and Chatlas and Jordan, respectively. McBryde 8 suggested values of K c1 between 0.1 and 0.015 M, depending on assumptions used in the analysis of spectrophotometric data.…”

Section: Resultssupporting

confidence: 87%

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Kinetics of Dissociation of Iron(III) Complexes of Tiron in Aqueous Acid

Zhang

Jordan

1996

Inorg. Chem.

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The kinetics of dissociation of the mono, bis, and tris complexes of Tiron (1,2-dihydroxy-3,5-benzenedisulfonate) have been studied in acidic aqueous solutions in 1.0 M HClO(4)/NaClO(4), as a function of [H(+)] and temperature. In general, the kinetics can be explained by two reactions, (H(2)O)Fe(L)(n)(-1) + H(2)L right arrow over left arrow (H(2)O)Fe(L(n)H) + H(+) (k(n), k(-n)) and (HO)Fe(L)(n)(-1) + H(2)L right arrow over left arrow (H(2)O)Fe(L(n)H) (k(n)', k(-n)'), a rapid equilibrium, (H(2)O)Fe(L(n)H) right arrow over left arrow (H(2)O)Fe(L)(n) + H(+) (K(cn)), and the formation constant (H(2)O)Fe(L)(n)(-1) + H(2)L right arrow over left arrow (H(2)O)Fe(L)(n) + 2H(+). For n = 1, the reaction was observed at 670 nm, and at [H(+)] of 0.05-0.5 M at temperatures of 2.0, 14.0, 25.0, and 36.7 degrees C. For n = 2, the analogous conditions are 562 nm, at [H(+)] of 1.5 x 10(-3) to 1.4 x 10(-2) M at temperatures of 2.0, 9.0, and 14.0 degrees C. For n = 3, the conditions are 482 nm, at pH 4.5-5.7 in 0.02 M acetate buffer at temperatures of 1.8, 8.0, and 14.5 degrees C. The rate or equilibrium constants (25 degrees C) with DeltaH or DeltaH degrees (kcal mol(-1)) and DeltaS or DeltaS degrees (cal mol(-1) K(-1)) in brackets are as follows: for n = 1, k(1) = 2.3 M(-1) s(-1) (8.9, -27.1), k(-1) = 1.18 M(-1) s(-1) (4.04, -44.8), K(c1) = 0.96 M (-9.99, -33.6), K(f1) = 2.01 M (-5.14, -15.85); for n = 2, k(-2)/K(c2) = 1.9 x 10(7) (19.9, 41.5) and k(-2)'/K(c2) = 1.85 x 10(3) (1.4, -38.8) and a lower limit of K(c2) > 0.015 M; for n = 3, k(3) = 7.7 x 10(3) (15.8, 12.3), k(-3) = 1.7 x 10(7) (16.2, 28.9), K(c3) = 7.4 x 10(-5) M (4.1, -5.1), and K(f3) = 3.35 x 10(-8) (3.7, -21.7). From the variations in rate constants and activation parameters, it is suggested that the Fe(L)(2) and Fe(L)(3) complexes undergo substitution by dissociative activation, promoted by the catecholate ligands.

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Section: Resultssupporting

confidence: 87%

“…McBryde 8 suggested values of K c1 between 0.1 and 0.015 M, depending on assumptions used in the analysis of spectrophotometric data. If such small values are used in eq 3, then the calculated k 1 ‘ is 10−70 times larger than that from previous work. , …”

Section: Resultsmentioning

confidence: 66%

Kinetics of Dissociation of Iron(III) Complexes of Tiron in Aqueous Acid

Zhang

Jordan

1996

Inorg. Chem.

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“…Only one di‐iron complex, [Fe 2 (OH)Cl 2 ] + , without coordinated water molecule could be assigned exclusively to the hydroxo‐bridged structure. The exact composition of the dinuclear complex remains uncertain, but the fact that the [Fe 2 OCl 2 ] + complex was not seen in the spectrum favours the dihydroxo‐bridged form, as was also suggested previously 13, 26, 29, 30. On the other hand, Flynn9 suggested that the energy difference is small between Fe(OH) 2 Fe and FeOFe·H 2 O structures; both forms may exist in equilibrium in solution.…”

Section: Resultsmentioning

confidence: 63%

Identification of hydrolysis products of FeCl₃ · 6H₂O by ESI‐MS

et al. 2006

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The hydrolysis reactions of FeCl3 in 0.1 mM aqueous solutions were monitored by electrospray ionisation time-of-flight mass spectrometry (ESI-ToF-MS). In contrast to the other ionisation techniques, electrospray ionisation provides information on the composition of the elemental cores even in water and salt cluster ions. Therefore, the technique facilitates detection of the bonding of the chloride ions in the oxo-hydroxo-iron cores. A variety of mononuclear and polynuclear iron-oxohydroxo-chloride complexes were characterised from the cationic and anionic mass spectra of iron(III) solutions. Oxidation and reduction reactions of iron, as well as competition between OH- and Cl- ions within one iron core, were also observed.

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“…By treatment of ferric sulfate with potassium hydroxide at a Fe 2 (SO 4 ) 3 :KOH ratio of 7:3, the salt 4Fe 2 (SO 4 ) 3 · 10Fe(OH) 3 ·K 2 SO 4 ·6H 2 O has been formed [15]. This salt is evidently in the equilibrium with the soluble ion [Fe 3 (OH) 5 The constants in Eqs.…”

Section: Resultsmentioning

confidence: 99%

“…The decrease of the ratio till Fe 3+ :OH − = 0.34-0.40 leads to the sedimentation of the salt Fe(OH)SO 4 ·4Fe(OH) 3[15], which can be at equilibrium with the ion [Fe 5 (OH)13 (H 2 O) 17 ] 2+ in the solution. Therefore, ferric polyions with different number of metal ions in them is soluble in water and their structures depends on the pH of the solution.…”

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confidence: 99%