Figure shows that the rates and conversions were highest for those catalysts that possessed the bulkiest fumarate substituents (2, 6, 7). The reactivity ordering in Figure showed no clear relationship to the binding affinities detailed in Table . While the most reactive catalyst 2, which possesses a di-(t-butyl) fumarate ligand, also has the most favorable exchange energy for the 14 to 15 conversion, other complexes such o-tol precatalyst 7 exhibited excellent catalytic reactivity at room temperature, despite having a fumarate binding affinity that is too endergonic to undergo the 14 to 15 exchange under the reaction conditions (>14 kcal/mol above that of 1). This means that if ligand exchange were a necessary step for catalyst activation, 7 should be completely inactive.