As functional models for diiron-hydrogenases, [FeFe]-H2ase's, both simple dinuclear iron dithiolates such as (mu-SCH2CH2CH2S)[Fe(CO)3]2, and (mu-SCH2CH2S)[Fe(CO)3]2 and the related tetranuclear iron complex Fe4[MeC(CH2S)3]2(CO)8 function as catalysts for proton reduction to H2.  Although the Fe appears to be site of protonation, the sulfur ligands play an important role on modulating the electron density at Fe, the proton dissociation constants (pKa), and electrode reduction potentials (E0) of the complexes.  Sulfur also plays a more direct role in the oxygen sensitivity of these complexes as it, rather the Fe, is the site of oxygenation.  An exploration by density functional theory of these issues as they relate to the mechanism of protonation, reduction, and oxygenation will be described.

Sulfur ligands in model complexes for the hydrogenases

244th National Meeting (2012)

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