"Pulling-Out" N2 from Diazo Compounds by Iron Complex for Carbene Formation.

One of the main pathways to (metal)carbene formation proceeds via the decomposition of diazo compounds, which can be triggered thermally, photochemically, or by transition-metal mediation. An alternative pathway for carbene generation from diazo compounds is the "pulling-out" N2 by different reagents. Herein, we report an iron-mediated strategy for the homolytic cleavage of C═N bond in diazo compounds, enabling the generation of free carbenes and iron-dinitrogen complexes under mild conditions. The corresponding Fe-diazo intermediates were isolated and fully characterized by X-ray crystallography and NMR spectroscopy. Homolytic C-N bond cleavage occurs upon warming, affording a persistent (phosphino)(silyl)carbene. The kinetics of this process were further elucidated by Eyring analysis. Computational modeling highlighted the critical role of Fe → N π-backdonation in cleaving the C═N π bond. These findings establish a new mechanistic framework for metal-assisted dinitrogen extrusion from diazo compounds and offer valuable insights into controlled carbene generation.