Mechanism and steric course of octahedral aquation. Part X. The preparation, properties, aquation, and anation of some cis-bisunidentato-(1,4,8,11-tetra-azacyclotetradecane)cobalt(III) cations

Abstract

The preparation and characterisation of a series of complexes of the type, cis-[Co cyclam X₂]Y (X =½CO₃, Cl, Y = Cl; X = NO₂, N₃, NCS, Y = NO₃ and ½[PtCl₆]; cyclam = 1,4,8,11-tetra-azacyclotetradecane) and cis- and trans-[Co cyclam(H₂O)₂](ClO₄)₃ are reported. In all the preparative experiments, substitution takes place with complete retention of configuration although a slow subsequent isomerisation to the more stable trans isomer can be observed. The kinetics of the aquation of the cis-dichloro-cation have been studied over a range of temperature. This complex is some 15,000 times more labile than its trans isomer at 25°, the effect arising from a much lower activation energy. The anation of cis-[Co cyclam Cl H₂O]²⁺ by thiocyanate has also been investigated. The reactions of the cis isomer are compared with those of the trans isomers and also with those of the corresponding bis(ethylenediamine)complexes.