Kinetic and mechanistic analysis of ligand substitution of aquapentacyanoruthenate(II) in SDS medium by 4,4′bipyridine

Abstract

Substitution of coordinated water molecule from the coordination sphere of [Ru(CN)₅H₂O]³⁻ with nitrogen donor ligand 4,4′Bipyridine (BipY) was studied in anionic micellar medium under pseudo first order condition as a function of ionic strength, pH, reactants concentration and temperature at 390 nm λ_max of orange colored product [Ru(CN)₄BipY]²⁻. The reaction was independent of [Ru(CN)₅H₂O]³⁻ while it exhibited first order kinetics in [BipY] in the selected concentration range. The variation in ionic strength had negative effect on substitution rate. The surfactant SDS has negative charge similar to that of the complex [Ru(CN)₅H₂O]³⁻, therefore does not show any significant effect on the reaction rate except at concentration higher than critical micelle concentration. A suitable mechanism involving the ion pair dissociation of complex [Ru(CN)₅H₂O]³⁻ and ligand BipY has been proposed. The activation parameters ΔH^≠, ΔS^≠ and E_a with respect to the slowest step of the mechanism were computed which supports the proposed mechanistic scheme.

Graphical Abstract

Keywords:

• Aquapentacyanoruthenate(II)
• 4,4′bipyridine
• kinetics and mechanism
• ligand substitution
• activation parameters
• micellar medium

Acknowledgement

One of the authors Richa Rastogi is thankful to head department of chemistry, Lucknow University, Lucknow for providing necessary research facilities to perform this work for her Ph. D degree.