Kinetic and mechanistic studies on substitution reaction of aqua-ligands from cis-diaqua-bis[2-(m-tolylazo)-pyridine]ruthenium(II) ion with 2,2' -bipyridine in aqueous medium

Abstract

The kinetics of substitution of aqua-ligands from <em>cis</em>-diaqua-bis[2-(<em>m</em>-tolylazo)pyridine]ruthenium(II) ion by 2,2'-bipyridine in aqueous medium has been studied spectrophotometrically at different temperatures (40-55°C). A rate law has been established. The reaction rates are found to be <em>p</em>H dependent in the <em>p</em>H range of 4.5 to 6.0. Ionic strength has a very little effect on the rate constants. Activation parameters (<img src='http://www.niscair.res.in/jinfo/delta.gif' border=0><em>H</em>^≠ and <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0><em>S</em>^≠) have been evaluated and compared with the reactions by 8-hydroxyquinoline and 1, 10- phenanthroline. All the experimental results are consistent with a dissociative mechanism. The effect of variation of dielectric constant of the medium has been used to verify the mechanistic conclusion.