Bond distances outer sphere mechanisms

The importance of the energy required to change metal—ligand bond distances is suggested by the fact that V2 + and Cr2+ both appear to react with substitution-inert [Co(NH3)0]3+ by an outer-sphere mechanism. However, V2+ reacts the faster, despite the fact that the redox potential is more favorable with Cr2 +. This can be understood since the Crn(f se9) to Cr 11 ( ,) oxidation presumably requires more reorganization of bond... 

In contrast to outer-sphere reactions, the simple observation that a reaction occurs by an inner-sphere mechanism necessarily introduces an element of structural definition. The relative dispositions of the oxidizing and reducing agents are immediately established and, except for structurally flexible bridging ligands such as NC5H4(CH2) C5H4N, the internuclear separation between redox sites can be inferred from known bond distances. Even so, bimolecular inner-sphere reactions necessarily occur by a sequence of elementary steps (Scheme 2) and the observed rate constant may include contributions from any of the series of steps. 

There are two widely accepted mechanisms for adsorption of solutes by a solid surface. Outer-sphere surface complexation, or non-specific adsorption, involves the electrostatic attraction between a charged surface and an oppositely charged ion in solution (Fig. 3). The adsorbed ion resides at a certain distance from the mineral surface. Inner-sphere complexation, also termed specific adsorption, involves the formation of a coordinative complex with the mineral surface (Kingston et al., 1972 Fig. 3). Inner-sphere complex bonds are more difficult to break than outer-sphere complex bonds and result in stronger adsorption of ions. 

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