Substitution kinetics in the complexes of pentacyanoruthenate(II) with ethylenediamine
The salt Na3[Ru(CN)5(en)]·2H2O (en = ethylenediamine) has been prepared and characterized by its IR and electronic spectral properties. The dissociation rate constant, k-L, was found to be dependent on pH, as expected from the protonation of the unbound N-site of the en ligand. From the values of k-...
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1989
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_02775387_v8_n17_p2091_Tokman http://hdl.handle.net/20.500.12110/paper_02775387_v8_n17_p2091_Tokman |
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| Sumario: | The salt Na3[Ru(CN)5(en)]·2H2O (en = ethylenediamine) has been prepared and characterized by its IR and electronic spectral properties. The dissociation rate constant, k-L, was found to be dependent on pH, as expected from the protonation of the unbound N-site of the en ligand. From the values of k-en = 6.2 × 10-5 s-1 and k-Hen+ = 1.07 × 10-4 s-1 (25°C) and activation parameter data, as well as considering the dependence of the rate on the concentration of reactants, a dissociative mechanism was postulated. The pKa of the Hen+ ligand was shown to be 9.7 (25°C), only slightly lower than for free (aqueous) Hen+ (9.98). The formation rate constants, kL, were determined for L = en (0.89 M-1 s-1) and L = Hen+ (0.83 M-1 s-1); the kinetic analysis suggests an ion pair-dissociative interchange mechanism, as well as the action of solvation effects. From k-L and kL, values of the stability constants, Kst (M-1), were calculated. A comparative discussion is made with the aid of data from related complexes of the [Ru(CN)5L]n- and [Fe(CN)5L]n- series. © 1989. |
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