Sulfur Oxygenates of Biomimetics of the Diiron Subsite of the [FeFe]-Hydrogenase Active Site: Properties and Oxygen Damage Repair Possibilities Academic Article uri icon

abstract

  • This study explores the site specificity (sulfur vs the Fe-Fe bond) of oxygenation of diiron (FeIFeI and FeIIFe II) 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′ = PMe 3 (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 Fe II(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. © 2009 American Chemical Society.

published proceedings

  • Journal of the American Chemical Society

author list (cited authors)

  • Liu, T., Li, B., Singleton, M. L., Hall, M. B., & Darensbourg, M. Y

citation count

  • 65

complete list of authors

  • Liu, Tianbiao||Li, Bin||Singleton, Michael L||Hall, Michael B||Darensbourg, Marcetta Y

publication date

  • May 2009