Influence of electrolytic dissociation upon rates of reactions. Part 9. The aquation of chloro- and bromo-penta-amminecobalt(III) and of -penta-amminechromium(III) in aqueous and 10% ethanol solutions of sulphate and dicarboxylates

Abstract

Rate coefficients (k) for aquation of [Co(NH₃)₅X]²⁺(X = Br or Cl) in 10% ethanol solutions of some dicarboxylates and sulphate have been determined by spectrophotometry, potentiometric titrations, and e.m.f. changes with time of a cell comprising glass and silver halide electrodes. Similar work has been done with the corresponding complexes of chromium(III) in aqueous solutions. The dissociation constants of the ion pairs formed have been obtained from the e.m.f.s of a cell comprising glass and calomel electrodes. A wide range of values of k(ion), k(ion pair), and dissociation constants has been obtained and in general there is a correlation between k(ion pair)/k(ion) and the dissociation constants for the dicarboxylate series. That for the sulphate series is characteristic of this ligand.