Diiron Bridged-Thiolate Complexes That Bind N₂ at the FeᴵᴵFeᴵᴵ, FeᴵᴵFeᴵ, and FeᴵFeᴵ Redox States
All known nitrogenase cofactors are rich in both sulfur and iron and are presumed capable of binding and reducing N₂. Nonetheless, synthetic examples of transition metal model complexes that bind N₂ and also feature sulfur donor ligands remain scarce. We report herein an unusual series of low-valent diiron complexes featuring thiolate and dinitrogen ligands. A new binucleating ligand scaffold is introduced that supports an Fe(μ-SAr)Fe diiron subunit that coordinates dinitrogen (N₂-Fe(μ-SAr)Fe-N₂) across at least three oxidation states FeᴵᴵFeᴵᴵ, FeᴵᴵFeᴵ, and FeᴵFeᴵ). The (N₂-Fe(μ-SAr)Fe-N₂) system undergoes reduction of the bound N₂ to produce NH₃ (∼50% yield) and can efficiently catalyze the disproportionation of N₂H₄ to NH₃ and N₂. The present scaffold also supports dinitrogen binding concomitant with hydride as a co-ligand. Synthetic model complexes of these types are desirable to ultimately constrain hypotheses regarding Fe-mediated nitrogen fixation in synthetic and biological systems.
© 2015 American Chemical Society. Received: May 7, 2015; Published: June 3, 2015. This work was supported by the NIH (GM 070757) and the Gordon and Betty Moore Foundation. We thank Larry Henling and Michael Takase for crystallographic assistance.
Supplemental Material - ja5b04738_si_001.pdf
Supplemental Material - ja5b04738_si_002.cif
Accepted Version - nihms-726889.pdf