Elucidating the structure of a high-spin σ-phenyliron(iii) species in a live FeCl₃-PhZnCl reaction system

Environmentally benign iron catalysts promote a wide variety of chemical transformations; however, insight into the mechanism and active intermediates is far from satisfactory, and the main difficulties lie in directly "seeing" the active species under "live" catalytic conditions. Herein, an unknown sextet Ph(THF)FeCl₂ species was well-characterized in a live FeCl₃-PhZnCl reaction system for the first time by Raman, in situ IR, electron paramagnetic resonance (EPR), X-ray absorption spectroscopic (XAS) and density functional theory (DFT) calculations. This work provides insight into the structure and reactivity of catalytically relevant σ-aryliron(iii) species, and shall provide useful guidelines for understanding iron chemistry.