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

• Published in: European journal of inorganic chemistry Vol. 2016; no. 9; pp. 1319 - 1332
• Main Authors: Folkertsma, Emma, de Waard, Esther F., Korpershoek, Gerda, van Schaik, Arnoldus J., Solozabal Mirón, Naiara, Borrmann, Mandy, Nijsse, Sjoerd, Moelands, Marcel A. H., Lutz, Martin, Otte, Matthias, Moret, Marc-Etienne, Klein Gebbink, Robertus J. M.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.03.2016; WILEY‐VCH Verlag; Wiley
• Subjects: Analogue; Chemistry; Chemistry, Inorganic & Nuclear; Coordination compounds; Enzyme models; Enzymes; Epoxidation; Esters; Facial; Iron; Ligands; Metalloenzymes; N,O ligands; Non-heme iron; O ligands; Physical Sciences; Science & Technology; DIOXYGEN ACTIVATION; N,N,O LIGANDS; HETEROSCORPIONATE LIGANDS; ACTIVE-SITES; FUNCTIONAL MODELS; CRYSTAL-STRUCTURES; Iron; Non-heme iron; Enzyme models; Metalloenzymes; N,O ligands; STRUCTURE VALIDATION; DONOR LIGANDS; Epoxidation; OLEFIN CIS-DIHYDROXYLATION; IRON(III) COMPLEXES
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201501406

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, BMBMeIP and its ester analogue, BMBMeIPnPr are designed to prevent the formation of previously reported coordinatively saturated FeL2 type complexes. The crystal structure of [Fe(BMBMeIPnPr)(OTf)2] shows a facial N,N,O‐coordination that is very similar to the structure of the enzyme active sites. Both [Fe(BMBMeIPnPr)(OTf)2] and [Fe(BMBMeIP)(OTf)(MeCN)n] catalyze the epoxidation of olefins using H2O2, 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. Mononuclear iron(II) complexes with a single facially coordinating N,N,O‐ligand were synthesized as accurate structural mimics of the 2‐His‐1‐carboxylate facial triad found in mononuclear non‐heme iron enzymes. The new [FeLOTfn] complexes provide three readily available coordination sites and show catalytic activity in epoxidation reactions.