The acid-catalysed aquations of cis[Co en2(N3)2]+ and cis and trans[Co en2(NO2)2]+ ions have been studied over a wide range of acid concentration. The results, together with those for several other systems, have been analysed by various methods. The results indicate that at the higher acid concentrations studied these cations all aquate via a unimolecular dissociation of the protonated complex. At lower acid concentrations it is difficult to distinguish between the SN1 CA and SN2CA mechanisms.
