Structural and Electronic Complexities of a Sulfur‐Bridged Di‐Iron Complex Composed of Mono‐ and Di‐Nitrosyl Units

Year: 2025

Type: article

Abstract: The delocalized, thermodynamically stable cation, [(N 2 S 2 )Fe(NO)•Fe(NO) 2 ] + , an adduct of mono‐nitrosyl and dinitrosyl iron units, is analyzed to address the unusual stability of the sulfur‐bridged diiron complex in its three overall redox levels, +, 0, and −. X‐ray diffraction and myriad spectroscopic techniques probe products of sequential electron uptake in the corresponding neutral and anionic species. Conundrums include unified blueshifts of the overall 3‐band, ν(NO), pattern with added electrons. One‐electron reduction changes the anti‐ferromagnetically coupled, S = 0, cationic diiron species to the neutral analog, S = ½, with unpaired spin mainly localized on the MNIU, which decreases its ∠Fe–N–O angle by 10 degrees in response to the extra electron density. Subsequent reduction to the anionic species, S = 1, involves a major geometric change at the MNIU, which moves the Fe in {Fe(NO)} 8 out of the N 2 S 2 plane. Site‐specific 15 N labeling of nitrosyl in the MNIU confirms the IR analysis and shows rapid NO exchange between the MNIU/DNIU (mono‐nitrosyl iron unit/dinitrosyl iron unit) pairs during its synthesis at RT. Mössbauer spectroscopy, S K‐edge XAS, and molecular orbital calculations confirm the ability of NO and the versatility of sulfur bridges to buffer and distribute electrons, a key to their major importance in metalloenzymes.

Source: Advanced Science

DOI: 10.1002/advs.202513976

Authors: Sarnali Sanfui, Manuel Quiroz, Jialu Li, Yang Ha, Feipeng Yang, Jinghua Guo, Nattamai Bhuvanesh, Brad S. Pierce, Perla B. Balbuena, Paul A. Lindahl, Michael B. Hall, Marcetta Y. Darensbourg

Institutions: Texas A&M University, Lawrence Berkeley National Laboratory, Advanced Light Source, Brookhaven National Laboratory, National Synchrotron Light Source II, University of Alabama

Language: English

Topic: Metal-Catalyzed Oxygenation Mechanisms

Subfield: Inorganic Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $6,730

Funders: National Science Foundation, U.S. Department of Energy, Office of Science, High Performance Research Computing, Texas A and M University, Division of Chemistry, Basic Energy Sciences, Lawrence Berkeley National Laboratory

OpenAlex ID: W4415618789