Kinetic studies on 4d and 5d transition metal complexes. Part I. The kinetics of the reactions of chloro-, bromo-, and iodo-pentammine-rhodium(iii) perchlorates with sodium hydroxide in aqueous solutions

Abstract

The kinetics of the reactions [R(NH₃)₅X]²⁺+ OH^–→[R(NH₃)₅OH]²⁺+ X^–(X = Cl, Br, I) have been studied over a range of temperatures under conditions which allow the calculation of second-order rate constants at zero ionic strength.

The results are in agreement with the Brönsted–Bjerrum theory of the primary salt effect at all temperatures. The reaction rates increase in the order Cl, Br, I, which is the reverse of the order of the ligand field strengths of the replaced ions and also the reverse of the rate order found in the Co^III series.