769-772The kinetics of the reversible complexation of oxalatopentaamminecobalt(III) with Ni2+ has been investigated at 15-30° C and I = 0.30 mol dm-3] At 25°C, kf, = (2.98±0.31) 103 dm3mol-1s-1, ∆H = 54.5 ±3.7 kJmol-1, ∆S = +3.3 ± 12.3 JK-1 mol-1 , and Kr, = (57.9 ± 2.2)s-1, ∆H = (60.4 ± 1.5) kJ mol-1, ∆S = - 8.8 ± 5.0 JK -1 mol-1, where kf and kr denote the rate constants for the formation and dissociation of the binuclear species,(NH3)5CoC2O4Ni3+ respectively. It is likely that the binuclear species exists in equilibrium between its monodentate and chelated forms, the half bonded oxalate moiety of the cobalt (III) substrate acting as a chelating ligand. This dissociation of Ni2+ from themonodentate form of the binuclear species is rate-limiting while the formation of such a species from the reactants is predominantly governed by the rate-limiting water dissociation from Ni(OH2)
