A Terminal Imido Complex of an Iron–Sulfur Cluster

• Published in: Angewandte Chemie International Edition Vol. 60; no. 23; pp. 12802 - 12806
• Main Authors: Sridharan, Arun, Brown, Alexandra C., Suess, Daniel L. M.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.06.2021
• Edition: International ed. in English
• Subjects: bioinorganic chemistry; cluster compounds; Clusters; Computer applications; C−H activation; Electrons; Hydrogen atoms; Iron; multiple bonds; Oxidation; Sulfur; cluster compounds; C−H activation; multiple bonds; bioinorganic chemistry
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202102603

We report the synthesis and characterization of the first terminal imido complex of an Fe–S cluster, (IMes)3Fe4S4=NDipp (2; IMes=1,3‐dimesitylimidazol‐2‐ylidene, Dipp=2,6‐diisopropylphenyl), which is generated by oxidative group transfer from DippN3 to the all‐ferrous cluster (IMes)3Fe4S4(PPh3). This two‐electron process is achieved by formal one‐electron oxidation of the imido‐bound Fe site and one‐electron oxidation of two IMes‐bound Fe sites. Structural, spectroscopic, and computational studies establish that the Fe–imido site is best described as a high‐spin Fe3+ center, which is manifested in its long Fe−N(imido) distance of 1.763(2) Å. Cluster 2 s hydrogen atoms from 1,4‐cyclohexadiene to yield the corresponding anilido complex, demonstrating competency for C−H activation. The first terminal imido complex of an iron–sulfur cluster has been synthesized and fully characterized. Structural, spectroscopic, and computational analysis suggest an [Fe4S4]2+=[NAr]2− formulation with a localized high‐spin Fe3+ valence at the imido‐bound site, and reactivity studies demonstrate competence for C−H activation.