An S = / Iron Complex Featuring N, Thiolate, and Hydride Ligands: Reductive Elimination of H and Relevant Thermochemical Fe-H Parameters.

Believed to accumulate on the Fe sites of the FeMo-cofactor (FeMoco) of MoFe-nitrogenase under turnover, strongly donating hydrides have been proposed to facilitate N binding to Fe and may also participate in the hydrogen evolution process concomitant to nitrogen fixation. Here, we report the synthesis and characterization of a thiolate-coordinated Fe(H)(N) complex, which releases H upon warming to yield an Fe-N-Fe complex. Bimolecular reductive elimination of H from metal hydrides is pertinent to the hydrogen evolution processes of both enzymes and electrocatalysts, but well-defined examples are uncommon and usually observed from diamagnetic second- and third-row transition metals. Kinetic data obtained on the HER of this ferric hydride species are consistent with a bimolecular reductive elimination pathway, arising from cleavage of the Fe-H bond with a computationally determined BDFE of 55.6 kcal/mol.