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)(mu-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 mu-hydrido isomer, which is unreactive toward protons.