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

The interaction of the aqua ligand substitution from cis-diaqua-bis(bipyridyl) ruthenium(II)complex([Ru(bpy)₂(H₂O)₂]²⁺) and hydroxopentaaqua rhodium(III) complex ([Rh(H₂O)₅(OH)]⁺²) by azide has been studied spectrophotometrically as a function of [substrate complex], [ligand] and temperature at pH 4.5 for the first complex and pH 4.3 for the second complex, at constant ionic strength. The substitution reaction for both complexes shows two consecutive steps. Both steps are [ligand]-dependent. The activation parameters for both steps were evaluated. Thermodynamic parameters calculated from the temperature dependence of the outer-sphere association equilibrium constants are also consistent with an associative mode of activation. The products of the reactions have been characterised by IR, and ESI-mass spectroscopic analysis.