Sulfur Oxygenates of Biomimetics of the Diiron Subsite of the [FeFe]-Hydrogenase Active Site: Properties and Oxygen Damage Repair Possibilities
(2009) Journal of the American chemical society — Vol. 131, p. 8296-8307 (2009)
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- Abstract
- This study explores the site specificity (sulfur vs the Fe-Fe bond) of oxygenation of diiron (FeIFeI and FeIIFeII) organometallics that model the 2-iron subsite in the active site of [FeFe]-hydrogenase: (μ-pdt)[Fe(CO)2L][Fe(CO)2L′] (L ) L′ ) CO (1); L ) PPh3, L′ ) CO (2); L ) L′ ) PMe3 (4)) and (μ-pdt)(μ-H)[Fe(CO)2PMe3]2 (5). DFT computations find that the Fe-Fe bond in the FeIFeI diiron models is thermodynamically favored to produce the μ-oxo or oxidative addition product, FeII-O-FeII; nevertheless, the sulfur-based HOMO-1 accounts for the experimentally observed mono- and bis-O-atom adducts at sulfur, i.e., (μ-pst)[Fe(CO)2L][Fe(CO)2L′] (pst ) -S(CH2)3S(O)-, 1,3-propanesulfenatothiolate; L ) L′ ) CO (1-O); L ) PPh3, L′ ) CO (2-O); L ) L′ ) PMe3 (4-O)) and (μ-pds)[Fe(CO)2L][Fe(CO)2L′] (pds )-(O)S(CH2)3S(O)-, 1,3-propanedisulfenato; L ) PPh3, L′ ) CO (2-O2)). The FeII(μ-H)FeII diiron model (5), for which the HOMO is largely of sulfur character, exclusively yields S-oxygenation. The depressing effect of such bridging ligand modification on the dynamic NMR properties arising from rotation of the Fe(CO)3 correlates with higher barriers to the CO/PMe3 exchange of (μ-pst)[Fe(CO)3]2 as compared to (μ-pdt)[Fe(CO)3]2. Five molecular structures are confirmed by X-ray diffraction: 1-O, 2-O, 2-O2, 4-O, and 6. Deoxygenation with reclamation of the μ-pdt parent complex occurs in a proton/electron-coupled process. The possible biological relevance of oxygenation and deoxygenation studies is discussed.
- Affiliations
Texas A M University (USA) Department of Chemistry
Citations
Liu, T., Li, B., Singleton, M., Hall, M. B., & Darensbourg, M. Y. (2009). Sulfur Oxygenates of Biomimetics of the Diiron Subsite of the [FeFe]-Hydrogenase Active Site: Properties and Oxygen Damage Repair Possibilities. Journal of the American chemical society, 131, 8296-8307. https://doi.org/10.1021/ja9016528 (Original work published 2009)