Kinetics and mechanism of the reaction of hydroxopentaaquarhodium(III) ion with l-Arginine in aqueous solution

Abstract

The kinetics of the aqua ligand substitution from hydroxopentaaquarhodium(III) ion, [Rh(H 2 O) 5 (OH)] 2? , by L-Arginine has been studied spectrophotometrically as a function of Arginine concentration, and temperature, at pH 4.3. The reaction proceeds via a rapid outer sphere association complex formation step followed by two consecutive steps. The first of these involves ligand-assisted anation, while the second involves chelation as the second aqua ligand is displaced. The association equilibrium constant for the outer sphere complex formation has been evaluated together with the rate constants for the two subsequent steps. The activation parameters for both steps have been evaluated using Eyring's equation. Thermodynamic parameters calculated from the temperature dependence of the outer sphere association equilibrium constants are also consistent with an associative mode of activation. The product of the reaction has been characterized by conductivity measurement and IR spectroscopic analysis.

Interaction of Glycyl – Glycine with Hydroxopentaaquarhodium(Iii) Ion in Aqueous Medium: Kinetic and Mechanistic Studies

“…The rate constant for the first path of the reaction was calculated from the absorbance data using the Weyh and Hamm [23] equation, as discussed before [24]. The k 1ðobsÞ values are collected in Table 1.…”

Kinetic and Mechanistic Studies on the Interaction of Azide Ion with cis-diaqua-bis(bipyridyl) ruthenium(II) Complex and Hydroxopentaaqua Rhodium(III) complex in Aqueous Medium

“…For dipeptides, the reaction has been found to proceed via two parallel paths: both processes are liganddependent [14,22]. But in the case of amino acids, it follows a consecutive rate law where the first path proceeds via an associative interchange activation and the second step is the ligand-independent ring closure [21] and for azide, both the steps are ligand-dependent and both follow two distinct associative interchange modes. Here also the steric and electronic effects are the two important factors for assigning the order of reactivity.…”