Reactions of FeFe-hydrogenase models involving the formation of hydrides related to proton reduction and hydrogen oxidation

FeFe-hydrogenases are enzymes in nature that catalyze the reduction of protons and the oxidation of H2 at neutral pH with remarkably high activities and incredibly low overpotential. Structural and functional biomimicking of the active site of FeFe-hydrogenases can provide helpful hints for elucidating the mechanism of H2 evolution and uptake at the FeFe-hydrogenase active site and for designing bioinspired catalysts to replace the expensive noble metal catalysts for H2 generation and uptake. This perspective focuses on the recent progress in the formation and reactivity of iron hydrides closely related to the processes of proton reduction and hydrogen oxidation mediated by diiron dithiolate complexes. The second section surveys the bridging and terminal hydride species formed from various diiron complexes as well as the intramolecular proton transfer. The very recent progress in H2 activation by diiron dithiolate models are reviewed in the third section. In the concluding remarks and outlook, the differences in structure and catalytic mechanism between the synthetic models and the native FeFe-H2ase active site are compared and analyzed, which may cause the need for a significantly larger driving force and may lead to lower activities of synthetic models than the FeFe-H2ases for H2 generation and uptake.