Carbon Monoxide and Cyanide Ligands in a Classical Organometallic Complex Model for Fe-Only Hydrogenase

Abstract

The Fe(I) organometallic complex [(µ-SCH(2)CH(2)CH(2)S)Fe(2)(CO)(6)] provides a structural model for the cyano-carbonyl diiron site of Fe-only hydrogenase as characterized by X-ray crystallography (the picture shows the structure (black) of the model overlaid with that of the Fe-Fe dimetallic site in the hydrogenase isolated from Desulfovibrio desulfuricans). Cyanide substitution of CO occurs readily and provides spectroscopic references for the active site.

TDDFT modeling of the CO‐photolysis of Fe2(S2C3H6)(CO)6, a model of the [FeFe]‐hydrogenase catalytic site

“…Accordingly, the two Fe atoms are classified as syn or anti regarding the ground state PBE0 PES, the 1 global minimum has C s symmetry (Scheme ). Optimized FeFe bond distance is 2.481 Å which is in line with the extendend X‐ray absorption fine structure (EXFAS) measure of 2.485 Å, but underestimated with respect to the X‐ray diffraction (XRD) measure of 2.5103 Å . The optimized cis and trans FeC bond distances differ only by 0.01 Å.…”

Investigation of Bridgehead Effects on Reduction Potential in Alkyl and Aryl Azadithiolate‐Bridged (µ‐SCH2XCH2S) [Fe(CO)3]2 Synthetic Analogues of [FeFe]‐H2ase Active Site

“…The crystallographic data on a series of (µ‐SCH 2 XCH 2 S)[Fe(CO) 3 ] 2 (where X = CH 2 , NMe , N‐ t Bu , N – Ar – Y ) complexes (Table S1) are obtained from literature , , . An interesting feature in this series, that has been identified and deemed important before, is the (OC) ap Fe‐ ‐ ‐Fe(CO) ap dihedral angle (i.e.…”

De novo design of functional proteins: Toward artificial hydrogenases

“…Structural mimics of the [FeFe] hydrogenase were first developed based on a (μ‐S(CH 2 ) 3 ‐S)[Fe 2 (CO) 6 ] complex, whose similarity to the enzyme's active site was initially recognized by Pickett, Darensbourg, and Rauchfuss (Figure ) . These mimics revealed features such as the need for a thermodynamically disfavored “rotated” state of the distal iron in the diiron cluster, which frees a position for catalysis, and electron‐donating ligands on the same iron atoms; further second‐sphere requirements include a pendant base that delivers protons to the active site, and a redox active group to ferry electrons during catalysis .…”

“…Placing the Dt amino acid at position 16 in the sequence facilitates i, i + 3 interactions with the C‐terminal Lys 19. The [2Fe2S] cluster was incorporated into purified peptide 1 by direct reaction with Fe 3 (CO) 12 under strictly anaerobic conditions to reconstruct the diiron containing active site of natural hydrogenases.…”