In:
Progress in Reaction Kinetics and Mechanism, SAGE Publications, Vol. 37, No. 2 ( 2012-05), p. 147-160
Abstract:
The kinetics of the palladium(II)-catalysed ligand exchange of the hexacyanoferrate(II) complex ion with 4-Cyanopyridine (4-CNpy) in aqueous acidic medium have been investigated at 25.0 ∓ 0.1 °C, pH 3.2 ∓ 0.02 and ionic strength, I=0.1 M (KNO 3 ). The reaction was followed spectrophotometrically by measuring the increase in absorbance of the intense cherry red complex [Fe(CN) 5 4-CNpy] 3 -, corresponding to metal-to-ligand charge transfer (MLCT) transitions, atλ. max 477 nm. The effects of pH, ionic strength, the concentrations of [Fe(CN) 5 4- ], Pd 2+ and 4-CNpy on the reaction rate have been studied and analysed. The kinetic data suggest that substitution follows an interchange dissociative (I d ) mechanism and occurs via formation of a solvent-bound intermediate. The effects of the dielectric constant of the medium on the reaction rate have been used to visualize the formation of a polar activated complex and an interchange dissociative mechanism for the reaction. A most probable mechanism has been proposed in order to interpret the kinetic data. Kinetic evidence is reported for the displacement of CN - by 4-CNpy in [Fe(CN)6 4 -]. Activation parameters for the proposed reaction have been evaluated using an Eyring plot, and provided further support to the proposed mechanistic scheme.
Type of Medium:
Online Resource
ISSN:
1468-6783
,
1471-406X
DOI:
10.3184/146867812X13323352665981
Language:
English
Publisher:
SAGE Publications
Publication Date:
2012
detail.hit.zdb_id:
2018085-8
