Modeling the active site of [FeFe]-hydrogenase: Electro-catalytic hydrogen evolution from acetic acid catalysed by [Fe < inf > 2 < /inf > (μ-L)(CO) < inf > 6 < /inf > ] and [Fe < inf > 2 < /inf > (μ-L)(CO) < inf > 5 < /inf > (PPh < inf > 3 < /inf > )] (L=pyrazine-2,3-dithiolate, quinoxaline-2,3-dithiolate and pyrido[2,3-b]pyrazine-2,3-dithiolate)

Abstract

Compounds [Fe2{ μ-pydt}(CO)6] (pydt = pyrazine-2,3-dithiolate) (1), [Fe2{ μ-qdt}(CO)6] (qdt = quinoxaline-2,3-dithiolate) (2), [Fe2{ μ-ppdt}(CO)6] (ppdt = pyrido[2,3-b]pyrazine-2,3-dithiolate) (3), [Fe2 { μ-pydt}(CO)5PPh3] (4), [Fe2{ μ-qdt}(CO)5PPh3] (5) and [Fe2{ μ-ppdt}(CO)5PPh3] (6) have been synthesized in order to model the active sites of '[FeFe]-hydrogenase'. Compounds 1-6 have been characterized by routine spectral studies and unambiguously by single crystal X-ray crystallography. Supramolecular chemistry of compounds 1-6 have been described in terms of intermolecular interactions, observed in their respective crystal structures. Electro-catalytic hydrogen evaluation studies (from acetic acid) have been performed using compounds 1-6 as electro-catalysts. The mechanistic aspects of relevant electro-catalytic proton reductions have been discussed in detail.