Work

Nitrogen Subvalency in a Four-Member Redox Series of Iron–Sulfur Cluster Imido Complexes

Year: 2025

Type: article

Abstract: Imido complexes of high-spin 3d metals can feature N subvalency, wherein configurations with hole character at N contribute significantly to the ground state electronic structure. Reported herein are the synthesis and characterization of a series of Fe–S cluster terminal imido complexes isolated in four charge states, [(IMes) 3 Fe 4 S 4 (NAr)] n (IMes, 1,3-dimesitylimidazol-2-ylidene; Ar = 2,4,6-tri- tert -butylphenyl; n = 1–, 0, 1+, 2+), in which the weak, trigonal ligand field of the sulfides enforces high-spin configurations at the Fe sites. It is shown that whereas the ground states of the anionic and neutral members of the series feature dominant imide ([NAr] 2– ) character, the mono- and dicationic clusters have significant imidyl ([NAr] •– ) and/or triplet nitrene ( 3 NAr) character. This was demonstrated experimentally using variable-temperature 1 H NMR spectroscopy to reveal the spin topology of the [Fe(NAr)] unit across the series. Additional structural, spectroscopic, and computational analysis revealed the extent to which electron density changes occur at the imido-bound Fe versus the peripheral Fe sites. These results establish the preference for high-spin Fe-imido sites in Fe–S clusters and the possibility for such sites to have multiconfigurational electronic structures with imide, imidyl, and/or nitrene character.

Source: Journal of the American Chemical Society

DOI: 10.1021/jacs.5c14036

Authors: Arun Sridharan, Daniel L. M. Suess

Institution: Massachusetts Institute of Technology

Language: English

Topic: Metalloenzymes and iron-sulfur proteins

Subfield: Renewable Energy, Sustainability and the Environment

Field: Energy

Domain: Physical Sciences

Open Access status: green

Funder: National Institute of General Medical Sciences

Awards: G3430150236, G4390353845