Transitional metal bases, correlation basicity

As mentioned above, successive occurrence of dehydration, dehydrogenation, and cross-coupling is required to yield the products. It seems likely that acid sites and base sites participate in the reaction. The role of base sites is particularly important because the conversion rates correlate well with the acidities of the reactants. Acidities of the reactants are compared to the reaction rates in Table 4.36. The pKa values are associated with the dissociation of the H atom which is abstracted in the cross-coupling step. The easier the dissociation of the H atom as an H, the faster the reaction rate. This suggests that abstraction of the H from the reactant by base sites is the ratedetermining step. Therefore, activity increase is caused by the increase in the basicity of MgO by doping with transition metal ions. The increase in basicity is prominent when the ionic radii of added metal ions are close to magnesium ion radius (see Section 3.2.2)... 

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