A Two‐State Reactivity Model Explains Unusual Kinetic Isotope Effect Patterns in C-H Bond Cleavage by Nonheme Oxoiron(IV) Complexes

Abstract
It's in the bond: The cleavage of CH bonds by two related oxoiron(IV) complexes shows a range of kinetic isotope effect (KIE) values that exhibit an unusual dependence on the CH bond strength. Large nonclassical KIEs are observed for bond strengths below 93 kcal mol−1, while semiclassical values are found above this value (see graph, DHA=9,10‐dihydroanthracene). This nonintuitive behavior can be rationalized by invoking a two‐state reactivity model.