Cobalt . ammine complexes inner-sphere reactions

The aquated Co(III) ion is a powerful oxidant. The value of E = 1.88 V (p = 0) is independent of Co(III) concentration over a wide range suggesting little dimer formation. It is stable for some hours in solution especially in the presence of Co(II) ions. This permits examination of its reactions. The CoOH " species is believed to be much more reactive than COjq Ref. 208. Both outer sphere and substitution-controlled inner sphere mechanisms are displayed. As water in the Co(H20) ion is replaced by NHj the lability of the coordinated water is reduced. The cobalt(III) complexes which have been so well characterized by Werner are thus the most widely chosen substrates for investigating substitution behavior. This includes proton exchange in coordinated ammines, and all types of substitution reactions (Chap. 4) as well as stereochemical change (Table 7.8). The CoNjX" entity has featured widely in substitution investigations. There are extensive data for anation reactions of... 

Many reactions have been studied using this reductant, and with inert oxidants, such as the ammine complexes of cobalt(in), there is the possibility of characterizing more fully the inner-sphere route in redox systems. 

Vanadium(II).—substantial amount of work has been undertaken using this reductant, especially in comparison of systems where Cr i has also been used as a reducing agent in order to identify possible reaction pathways. A number of kinetic data have been interpreted in terms of an inner-sphere mechanism with the rate of substitution of co-ordinated water on the metal ion as rate determining. In the reaction with azido-ammine complexes of cobalt(m), ... 

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