Spectrophotometric kinetic study of mercury(II)-catalyzed formation of [4-CNpyRu(CN)5]3− via ligand exchange reaction of hexacyanoruthenate(II) with 4-cyanopyridine: a mechanistic approach

Abstract

The kinetics of the formation of yellow-colored complex [4-CNpy Ru(CN)5]3− via cyanide substitution from the coordination sphere of [Ru(CN)6]4− using Hg(II) as catalyst by nitrogen heterocyclic ligand 4-cyanopyridine (4-CNpy) has been studied spectrophotometrically in an aqueous medium by monitoring the increment in absorbance at 400 nm, the λmax of yellow-colored product [4-CNpy Ru(CN)5]3−. The reaction rate followed first-order kinetics in [4-CNpy] and was independent to [Ru(CN)64−]. The complex behavior in the reaction rate was observed with increasing [Hg2+]. Negative salt effect upon variation in ionic strength was noticed in the progressive course of the reaction. A suitable mechanistic scheme compatible with the experimental results has been suggested which is supported by activation parameters.