An S =1/2 Iron Complex Featuring N_(2') Thiolate, and Hydride Ligands: Reductive Elimination of H_2 and Relevant Thermochemical Fe-H Parameters

摘要

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-2 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-III(H)-(N-2) complex, which releases H-2 upon warming to yield an Fe-II-N-2-Fe-II complex. Bimolecular reductive elimination of H-2 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.