Reactions in micellar solutions: Part 9†-Kinetics of base hydrolysis of cis-(imidazole)(salicylato)bis(ethylenediamine)cobalt(III) and (ɑβS)-(sulphito)(tetraethylenepentamine)cobalt(III) in the presence of neutral, anionic and cationic surfactants in aqueous medium

Abstract

The base hydrolysis of <em>cis-</em>(imidazolato)(salicylato)bis(ethylene-diamine)cobalt(III) is moderately catalysed by CTAB (cationic), retarded by SDS (anionic) and influenced only a little by Triton X-100 (neural). The rate retardation by SDS is due to the less reactive phenol species, <em>cis</em>- in which form the complex exists exclusively in the micellar pseudo-phase of S S. The rate of base hydrolysis of (a ~S)-(tetraethylenepentamine Xsulphito )cobalt(III)(stable S- onded isomer) is retarded by Triton X 100, SOS and CTAB, the effect increasing with increase in surfactant] in the order SOS > > Tliton-X-IOO> CTAB. The rate data for this substrate at varying [SOS] and [Triton X 100] are interpreted in terms of pseudo-phase equilibrium model taking into account ion-exchange in the case of SDS. The rate retardation by CTAB is due to the formation of less reactive premicellar aggregate (1:1 ion pair) of this substrate with the CTA⁺ cation. The roles of electrostatic and hydrophobic effects of the micelles on the hydrolysis reactions of the micelle-bound Co (III) substrates under consideration are discussed.