Iron-Catalyzed Cross-Coupling Reactions of Arylmagnesium Reagents with Aryl Chlorides and Tosylates: Influence of Ligand Structural Parameters and Identification of a General N‑Heterocyclic Carbene Ligand

A systematic evaluation of N-heterocyclic carbene ligands in the iron-catalyzed cross-coupling reactions of aryl chlorides and arylmagnesium reagents is performed. There is no clear correlation between the donor strength of the N-heterocyclic carbene and the reaction outcome. Instead, the highest yields of the desired biaryl product are obtained with sterically demanding ligands possessing large %<i>V</i><sub>bur</sub> values. Through this study, SIPrNap has been identified as an efficient and general ligand for the coupling of both aryl chlorides and tosylates.