Kinetic studies of the reaction between dihalodicarbonylrhodate(I) anions and 2-aminopyridine

The kinetic behavior of the reaction between dihalodicarbonylrhodate(I) anions, [RhX₂(CO)₂]⁻¹, where X = Cl, Br, and the chelating agent 2-aminopyridine was investigated spectrophotometrically. The reaction for both halo analogues was found to obey third order kinetics, first order in the complex anion and second order in the 2-aminopyridine concentrations. The third order rate constants for the chloro and bromo complex anions had the values, at 25°C, of 779 and 156 l² mol⁻² min⁻¹, respectively, and the corresponding activation energies were 3.00 and 5.50 Kcal mol⁻¹. A mechanism is proposed to account for these observations.