Substitution kinetics of <i>cis</i>-diaqua-bis-{2-(<i>m</i>-tolylazo)pyridine}ruthenium(II) ion with thiourea

Abstract

The kinetics and mechanism of substitution of <i>cis</i>-diaqua-bis-{ 2-(<i>m</i>-tolylazo )pyridine] ruthenium(ll) with thiourea have been investigated spectrophotometricaIly as a function of [substrate complex], ionic strength, <i>p</i>H<i>, </i> [thiourea], temperature and medium dielectric constant. The reaction rate is independent of ionic strength but dependent on <i>p</i>H in the <i>p</i>H range 4-6. The activation parameters measured for this system have been compared with those of similar systems. The reaction rates are insensitive to the nature of incoming ligands and a dissociative mechanism has been proposed. The decrease of reaction rate with decrease in medium dielectric constant is also a logical consequence of such mechanism.