Highly Activated Terminal Carbon Monoxide Ligand in an Iron–Sulfur Cluster Model of FeMco with Intermediate Local Spin State at Fe
Abstract
Nitrogenases, the enzymes that convert N2 to NH3, also catalyze the reductive coupling of CO to yield hydrocarbons. CO-coordinated species of nitrogenase clusters have been isolated and used to infer mechanistic information. However, synthetic FeS clusters displaying CO ligands remain rare, which limits benchmarking. Starting from a synthetic cluster that models a cubane portion of the FeMo cofactor (FeMoco), including a bridging carbyne ligand, we report a heterometallic tungsten–iron–sulfur cluster with a single terminal CO coordination in two oxidation states with a high level of CO activation (νCO = 1851 and 1751 cm–1). The local Fe coordination environment (2S, 1C, 1CO) is identical to that in the protein making this system a suitable benchmark. Computational studies find an unusual intermediate spin electronic configuration at the Fe sites promoted by the presence the carbyne ligand. This electronic feature is partly responsible for the high degree of CO activation in the reduced cluster.
Copyright and License
© 2024 The Authors. Published by American Chemical Society. This publication is licensed under CC-BY 4.0.
Acknowledgement
We are grateful to the National Institutes of Health (R01-GM102687B to T.A.) and the Humboldt Foundation for funding for T.A. (a Bessel Research Award) and J.P.J. We thank the Beckman Institute and the Dow Next Generation Grant for instrumentation support. Michael Takase and Lawrence Henling are thanked for assistance with crystallography. J.P.J. and S.D. acknowledge the Max Planck Society for funding.
Conflict of Interest
The authors declare no competing financial interest.
Data Availability
General methods, synthetic procedures, product isolation and characterization, NMR spectra, structural information, and computational methods (PDF)
2130433–2130434, 2130436, 2233067–2233070, and 2233072 contain the supplementary crystallographic data for this paper.
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Additional details
- ISSN
- 1520-5126
- PMCID
- PMC10910499
- National Institutes of Health
- R01- GM102687B
- Alexander von Humboldt Foundation
- California Institute of Technology
- Beckman Institute
- Dow Chemical (United States)
- Max Planck Society