Terminal hydride formation in [FeFe] hydrogenase: understanding the role of the dithiolate bridgehead

[FeFe]-hydrogenases are highly-active hydrogen-conversion biocatalysts using Earth-abundant metals in their active-site. Understanding their mechanism may enable design of catalysts for renewable energy storage. Here, observation of the crucial Fe-hydride-containing (Hhyd) intermediate in a PDT-variant of [FeFe]-hydrogenase reveals deeper insight into the role of the dithiolate bridgehead in the catalytic mechanism.