A Terminal Imido Complex of an Iron-Sulfur Cluster

We report the synthesis and characterization of the first terminal imido complex of an Fe-S cluster, (IMes)(3)Fe4S4=NDipp (2; IMes=1,3-dimesitylimidazol-2-ylidene, Dipp=2,6-diisopropylphenyl), which is generated by oxidative group transfer from DippN(3) to the all-ferrous cluster (IMes)(3)Fe4S4(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) angstrom. Cluster 2 abstracts hydrogen atoms from 1,4-cyclohexadiene to yield the corresponding anilido complex, demonstrating competency for C-H activation.

Automated summary

This study reports the synthesis and characterization of the first terminal imido complex of an Fe-S cluster, demonstrating competency for C-H activation. The Fe-imido site is described as a high-spin Fe3+ center, with a long Fe-N(imido) distance of 1.763(2) angstrom.