Facile H/D Exchange at (Hetero)Aromatic Hydrocarbons Catalyzed by a Stable Trans-Dihydride N-Heterocyclic Carbene (NHC) Iron Complex

Earth-abundant metal pincer complexes have played an important role in homogeneous catalysis during the last ten years. Yet, despite intense research efforts, the synthesis of iron PC carbene P pincer complexes has so far remained elusive. Here we report the synthesis of the first PC NHC P functionalized iron complex [(PC NHC P)FeCl 2 ] ( 1 ) and the reactivity of the corresponding trans -dihydride iron(II) dinitrogen complex [(PC NHC P)Fe(H) 2 N 2 )] ( 2 ). Complex 2 is stable under an atmosphere of N 2 and is highly active for hydrogen isotope exchange at (hetero)aromatic hydrocarbons under mild conditions (50 °C, N 2 ). With benzene- d 6 as the deuterium source, easily reducible functional groups such as esters and amides are well tolerated, contributing to the overall wide substrate scope (e.g., halides, ethers, and amines). DFT studies suggest a complex assisted σ-bond metathesis pathway for C(sp 2 )-H bond activation, which is further discussed in this study.