The kinetics and mechanism of the substitution reactions of the aquapentacyanoruthenate(II) ion with naphthalene-substituted ligands in aqueous medium

✍ Scribed by R. M. Naik; Ruchi Singh; Abhas Asthana

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 211 KB
• Volume: 43
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.20526

✦ Synopsis

Abstract

The kinetics and mechanism of substitution reaction of [Ru(CN)~5~H~2~O]^3−^ anion with two naphthalene‐substituted ligands viz. L^n^ = nitroso‐R‐salt (NRS) and α‐nitroso‐β‐naphthol (αNβN) have been studied spectrophotometrically by monitoring an increase in absorbance at λ~max~ = 525 nm corresponding to metal to ligand charge transfer (MLCT) transitions due to formation of substituted [Ru(CN)~5~L]^n−3^ as a function of pH, ionic strength, temperature, a wide range of ligands concentration, and [Ru(CN)~5~H~2~O^3−^] under pseudo‐first‐order conditions. The experimental observation suggests that [Ru(CN)~5~H~2~O]^3−^ ion interacts with both ligands, which finally get converted into corresponding, [Ru(CN)~5~L]^n−3^ complexes as a final reaction product. The reaction is found to obey first‐order dependence each in [Ru(CN)~5~H~2~O^3−^] and [L^n^]. The substituted products, viz. [Ru(CN)~5~L]^n−3^, in each case have strong MLCT transitions in visible region. The substitutional lability of [Ru(CN)~5~H~2~O]^3−^ has been discussed in terms of electronic effect on the M__OH~2~ bond interactions. The kinetic observation suggests that the complexation reaction of [Ru(CN)~5~H~2~O]^3−^ with both the ligands, i.e., NRS and αNβN, follows an ion pair dissociative mechanism. The thermal activation parameters Δ__H^≠^ and Δ__S__^≠^ have been calculated using Eyring's equation and provided in support for the proposed mechanistic scheme. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 43: 21–30, 2011