Spectroscopic and crystallographic evidence for the N-protonated (FeFeI)-Fe-I azadithiolate complex related to the active site of Fe-only hydrogenases

The complex [{(mu-SCH2)(2)N(CH2C6H4-2-Br)}Fe-2(CO)(6)] and its N-protonated species, as structural models of the Fe-only hydrogenase active site, were identified spectroscopically and crystallographically, and their molecular structures show the 0.04 - 0.1 angstrom lengthening of the three N-C bonds and an intramolecular H center dot center dot center dot Br contact (2.82 angstrom) in the crystalline state of the N-protonated species.