Ak. Ghosh et al., DISPLACEMENT OF AQUA-LIGANDS FROM THE HYDROXOPENTAAQUARHODIUM(III) ION BY PYRIDINE-2-ALDOXIME - A KINETIC AND MECHANISTIC APPROACH, Transition metal chemistry, 21(4), 1996, pp. 358-362
The kinetics of anation of the hydroxopentaaquarhodium(III) ion by pyr
idine-2-aldoxime have been studied spectrophotometrically as a functio
n of pH, substrate concentration, entering ligand, temperature and sol
vent polarity. The reaction rate increases with an increase in pH, tem
perature and ligand concentration, and reaches a limiting value at hig
h ligand concentration. The activation parameters (Delta H-not equal =
87.5 kJ mol(-1) and Delta S-not equal = -52.3 J K-1 mol(-1)) have bee
n calculated from an Eyring plot and are compared with aqua exchanges
in other systems. All the experimental facts lead to an associative in
terchange (I-a) mechanism with the prior formation of an outer-sphere
association complex. Solvent polarity effects lead to the same conclus
ion.