Theoretical Investigations into C–H Bond Activation Reaction by Nonheme Mn^IVO Complexes: Multistate Reactivity with No Oxygen Rebound

Recently published experimental results on a nonheme synthetic [(Bn-TPEN)­Mn^IVO]²⁺ complex reveal that it is capable of activating strong C–H bonds. However, the final products are shown to contain Mn^III instead of the expected Mn^II, which should be formed if a rebound mechanism similar to what is assumed for heme Fe^IVO was to occur. It was proposed that the substrate radical generated during H-abstraction dissociates from the Mn^IIIOH complex and undergoes an additional reaction to a second molecule of Mn^IVO, leading to Mn^III. Density functional calculations reveal the root cause of why a follow-up rebound to form Mn^II and alcohol is not preferred in this system. It is further shown that nonheme Mn^IVO has a more complex spin-state manifold during C–H activation reactions compared with Fe^IVO, and that spin-state matters in oxidative chemistry of metal-oxo reagents