Mimicry of the 2‐His‐1‐Carboxylate Facial Triad Using Bulky N,N,O‐Ligands: Non‐Heme Iron Complexes Featuring a Single Facial Ligand and Easily Exchangeable Co‐Ligands

Abstract

Abstract Mononuclear iron(II) complexes with facially coordinating N,N,O‐ligands were synthesized as accurate structural mimics of the 2‐His‐1‐carboxylate facial triad found in mononuclear non‐heme iron enzymes. Mimicking of the facial triad is achieved by designing sterically demanding ligands providing two histidine‐like benzimidazole moieties and a coordinating carboxylate or ester moiety. The new methyl‐substituted analogue of the bis(benzimidazolyl)propionate ligand, BMB Me IP and its ester analogue, BMB Me IP n Pr are designed to prevent the formation of previously reported coordinatively saturated FeL 2 type complexes. The crystal structure of [Fe(BMB Me IP n Pr )(OTf) 2 ] shows a facial N,N,O‐coordination that is very similar to the structure of the enzyme active sites. Both [Fe(BMB Me IP n Pr )(OTf) 2 ] and [Fe(BMB Me IP)(OTf)(MeCN) n ] catalyze the epoxidation of olefins using H 2 O 2 , reaching turnover numbers up to 5.8 per iron. These results represent the first examples of iron complexes bearing a single facial and rigid N,N,O‐coordinating ligand and three readily available coordination sites showing catalytic activity in oxidation reactions.