First insights into the protonation of dissymetrically disubstituted di-iron azadithiolate models of the [FeFelH_2ases active site

摘要

Dissymetrically disubstituted di-iron azadithiolate complexes [Fe_2(CO)_4(κ~2-LL){μ-SCH_2N(~iPr)CH_2S}] (LL = dppe, phen) protonate exclusively at the N atom of the bridge, like the hexacarbonyl precursor but in contrast to symmetrically disubstituted analogues; substitution of dppe for two CO groups noticeably increases the kinetics of the electrocatalytic proton reduction process.rnEfforts of synthetic chemists to design model compounds that would reproduce some of the key features of the H cluster, the organometallic active site of the iron-only hydrogenase . enzymes ([FeFe]H_2ase) led to a variety of complexes, built on {2Fe2S} or {2Fe3S} frameworks.3 However, while the pyramids enclosing the iron atoms are eclipsed in the model complexes, they are inverted in the H cluster, in which this thermodynamically less favourable arrangement is stabilised by the surrounding protein. DFT calculations recently indicated that the introduction of electron-donor ligands at a single Fe site should favour the "rotated" geometry.