While diazo compounds are commonly used as carbene precursors, certain metal complexes can trigger cyclization reactions in which the N2 motif is retained. Herein we report the reaction of diphenyldiazomethane (ddam) toward two isomeric iron complexes featuring possible proximal and distal cooperative ligand sites, respectively. While the reaction of ddam with one complex gives a simple end-on adduct, the reaction with the other complex leads to the intramolecular cyclization of ddam into indazole and proton migration facilitated by distal metal–ligand cooperation.
Ocampo et al. (2026) studied this question.