Artículo
Abstract:
Complexes of the [RuIII(edta)SR]n series, with SR- = deprotonated cysteine, N-acetylcysteine, 2-mercaptoethanol, glutathione and penicilamine, were prepared from [Ru(edta)H2O]- and the corresponding RSH thiols, at pH = 5.5. The complexes exhibit intense visible absorption bands at ca. 520 nm (ε ≅ 3500 M-1 cm-1), associated with LMCT from the sulfur ligands bound to RuIII. The kinetics of the formation reactions were first order in [RuIII(edta)H2O]- and thiol reactants, with k1 values ca. 1-5 × 102 M-1 s-1 (25°C) for all the sulfur ligands except penicilamine, which reacted slower by a factor of 10. Activation parameters suggest an associative mechanism, as for the coordination of other S-and N-bound ligands to [RuIII(edta)H2O]-. A reactivity decrease is apparent at low and high pH's (ranges 1-3 and 8-10, respectively), associated with acid-base equilibria involving the less reactive [RuIII(Hedta)H2O] and [RuIII(edta)OH]2- species. A significant rate increase was found for cysteine and penicilamine at ca. pH = 8.0, because the thiol reactants deprotonate. The equilibrium constants for all the ligands showed that robust complexes were formed, with K = ca. 1 × 105 M-1 (25°C). The dissociation rate constants, k-1, were in the 10-3-10-4 s-1 range. The influence of nucleophilic and steric effects increasing and decreasing the formation rates, respectively, is discussed for the thiolate ligands, with adequate comparisons with other L species bound to [RuIII(edta)H2O]-.
Registro:
| Documento: | Artículo |
| Título: | Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates |
| Autor: | Povse, V.G.; Olabe, J.A. |
| Filiación: | Depto. Quim. Inorg., Analitica y Q., Fac. de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón 2, 1428 Capital Federal, Argentina |
| Año: | 1998 |
| Volumen: | 23 |
| Número: | 6 |
| Página de inicio: | 657 |
| Página de fin: | 662 |
| DOI: | http://dx.doi.org/10.1023/A:1006992526138 |
| Título revista: | Transition Metal Chemistry |
| Título revista abreviado: | Transition Met Chem |
| ISSN: | 03404285 |
| CODEN: | TMCHD |
| Registro: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_03404285_v23_n6_p657_Povse |
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Citas:
---------- APA ----------
Povse, V.G. & Olabe, J.A. (1998) . Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates. Transition Metal Chemistry, 23(6), 657-662.http://dx.doi.org/10.1023/A:1006992526138
---------- CHICAGO ----------
Povse, V.G., Olabe, J.A. "Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates" . Transition Metal Chemistry 23, no. 6 (1998) : 657-662.http://dx.doi.org/10.1023/A:1006992526138
---------- MLA ----------
Povse, V.G., Olabe, J.A. "Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates" . Transition Metal Chemistry, vol. 23, no. 6, 1998, pp. 657-662.http://dx.doi.org/10.1023/A:1006992526138
---------- VANCOUVER ----------
Povse, V.G., Olabe, J.A. Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates. Transition Met Chem. 1998;23(6):657-662.http://dx.doi.org/10.1023/A:1006992526138
