Characterization of a Diferrous Terminal Hydride Mechanistically Relevant to the Fe-Only Hydrogenases

Reduction of diferrous dithiolato complexes with hydride donor reagents affords the first example of the previously elusive terminal diferrous hydride, [Fe2(edt)(μ-CO)(H)(CO)(PMe3)4]PF6 (edt = S2C2H4). Crystallographic characterization shows that this model contains an asymmetrical semi-bridging CO trans to a terminal hydrido, as indicated in the Hred state in the D. desulfuricans enzyme. The model reacts with protons to yield H2 and rearranges via an intramolecular process to the isomeric μ-hydrido isomer, which is unreactive toward protons.