Mechanism and steric course of octahedral aquation. Part IX. The stereoretentive aquation, anation, and base hydrolysis of the trans-dichloro(1,4,8,11-tetra-azacyclotetradecane)cobalt(III) cation and its solvento-derivatives
- 1 January 1967
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc. A
- p. 2069-2075
- https://doi.org/10.1039/j19670002069
Abstract
The aquation equilibria and kinetics of trans-[Co cyclam Cl2]+(cyclam = 1,4,8,11-tetra-azacyclotetradecane) have been studied over a range of temperature. The anation of trans-[Co cyclam H2O Cl]2+ by thiocyanate and chloride ions is reported and SCN– is shown to be a much more effective reagent than Cl–. The base hydrolysis of trans-[Co cyclam Cl2]+ is a fast, two-stage reaction and has been studied in buffer solutions. In the pH region 6·2 to 7·4 the first stage, which has a first-order rate dependence on [OH–], is rate-determining but at higher pH the second stage, whose rate is independent of pH, becomes distinguishible and eventually rate-determining. This stage is identified as the aquation of trans-[Co cyclam OH Cl]+ and the assignment confirmed by studies on the independently prepared hydroxochloro-cation. All the reactions reported proceed with complete retention of configuration. The behaviour of the cyclam complexes is compared with that of the corresponding bisethylene-diamine species.Keywords
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