The Third Hydrogenase: More Natural Organometallics

Abstract

The [Fe]-hydrogenase, also known as “H2-forming methylenetetrahydromethanopterin dehydrogenase” (Hmd) or “iron-sulfur cluster-free hydrogenase”, is the third distinct class of hydrogenase enzyme to be discovered. In the presence of its carbocation substrate, it catalyzes the reversible cleavage of dihydrogen into H+ and H-, placing the later concomitantly onto the substrate molecule. This review describes the emerging chemistry behind this fascinating enzyme

A Five‐Coordinate Iron Center in the Active Site of [Fe]‐Hydrogenase: Hints from a Model Study

“…[7,14] A number of smallmolecule mimics of [Fe]-hydrogenase have been reported. [15][16][17][18][19][20][21][22][23][24][25] To date, all of the advanced models that contain iron acyl or carbamoyl moieties [17,19,20,23,24] (2). [24] The sample of 1 prepared in situ was impure, and its reactions with monodentate thiolate ligands led to unidentified mixtures.…”

[FeFe] Hydrogenase: Protonation of {2Fe3S} Systems and Formation of Super‐reduced Hydride States

“…The solid-state structures of 2 and the {2Fe3S(m-H)} complex [3][PF 6 ] were confirmed by single-crystal X-ray crystallography (see the Supporting Information and Figure 1, (Figure 2, blue spectrum). Density functional theory (DFT) simulation supports the formulation of 3 as the mixed-valence 35-electron species in which no ligand rearrangement has occurred (Scheme 2; see the Supporting Information for calculated spectra).…”

“…These roles include nitrogen fixation, [1] hydrogen evolution/uptake by the [FeFe] and [NiFe] hydrogenases, [2] heterolytic cleavage of molecular hydrogen at [Fe] hydrogenase, [3,4] and such hydrides are likely involved in enzymic catalysis of the interconversion of CO 2 and CO.…”

“…These roles include nitrogen fixation, [1] hydrogen evolution/uptake by the [FeFe] and [NiFe] hydrogenases, [2] heterolytic cleavage of molecular hydrogen at [Fe] hydrogenase, [3,4] and such hydrides are likely involved in enzymic catalysis of the interconversion of CO 2 and CO. [5] They have an implicit role as intermediates in electrocatalytic bioinorganic systems which model natural processes. [6] Synthetic bridging hydride species at {2Fe2S} cores are structurally well-established [7][8][9] and the chemistry of terminal hydrides at such centers is rapidly developing.…”

“…Reaction of the known {2Fe3S}-pentacarbonyl 1 [14] with PMe 3 gave the complex 2, which was readily converted into [3][PF 6 ] by protonation (Scheme 1). The solid-state structures of 2 and the {2Fe3S(m-H)} complex [3][PF 6 ] were confirmed by single-crystal X-ray crystallography (see the Supporting Information and Figure 1, (Figure 2, blue spectrum).…”