Iron-catalyzed C–C coupling reactions of pyrrole provide a unique alternative to the traditional Pd-catalyzed counterpart. However, many details regarding the actual mechanism remain unknown. A series of macrocyclic iron(III) complexes were used to evaluate specifics related to the role of O₂, radicals, and μ-oxodiiron-complex participation in the catalytic cycle. It was determined that the mononuclear tetra-azamacrocyclic complex is a true catalyst and not a stoichiometric reagent, while more than one equivalent of a sacrificial oxidant is needed. Furthermore, the reaction does not proceed through an organic radical pathway. μ-Oxodiiron complexes are not involved in the main catalytic pathway, and the dimers are, in fact, off-cycle species that decrease catalytic efficiency.

中文翻译：

---

铁催化 C-H 键活化和 C-C 偶联的机理研究

铁催化的吡咯 C-C 偶联反应为传统的 Pd 催化反应物提供了独特的替代方案。然而，关于实际机制的许多细节仍然未知。一系列大环铁 (III) 配合物用于评估与 O ₂、自由基和 μ-氧二铁配合物参与催化循环的作用相关的细节。已确定单核四氮杂大环配合物是真正的催化剂而不是化学计量试剂，而需要多于一当量的牺牲氧化剂。此外，该反应不通过有机自由基途径进行。μ-Oxodiiron 配合物不参与主要催化途径，事实上，二聚体是降低催化效率的非循环物质。