Octahedral cobalt(III) complexes of the chloropentammine type. Part I. The release of chloride ions from the cis-chlorohydroxylaminebis-(ethylenediamine)cobalt(III) cation in neutral and in basic solutions

Abstract

The second-order rate constants for the hydrolysis of cis-chlorohydroxylaminebis(ethylenediamine)cobalt(III) cation by bases have been measured at 0° and ionic strength of 0·1M. The lower rate than of the cis-chloroammine complex is inconsistent with the S_N1CB mechanism, but supports a bimolecular rearrangement between the solvation shell and the co-ordination shell. It is suggested that ion-pair association is involved in the reaction. In neutral solutions the complex cation spontaneously releases chloride ions by a redox process at rates which are much lower than those of hydrolysis by base.