Roy, S; Laureanti, JA; Groy, TL; Jones, AK
To probe the influence of redox non-innocent ligands on a well-known class of [FeFe]-hydrogenase models, three new asymmetrically disubstituted diiron complexes of the general formula (mu-SRS)[Fe(CO)(3)][Fe(CO)(N-N)] {SRS = propane-1,3-dithiolate (pdt) or benzene-1,2-dithiolate (bdt), and N-N = 2,2-bipyridine (bipy) or 2,2-bipyrimidine (bpym)} have been synthesized from their parent hexacarbonyls and characterized. The new complexes, (mu-pdt)Fe-2(CO)(4)((2)-bpym) (2), (mu-bdt)Fe-2(CO)(4)((2)-bipy) (3), and (mu-bdt)Fe-2(CO)(4)((2)-bpym) (4), were fully characterized by spectroscopic and electrochemical techniques, and the results are compared to those of a related complex, (mu-pdt)Fe-2(CO)(4)((2)-bipy) (1). The crystal structures of 2-4 show that, in each complex, the two iron units are in an eclipsed orientation, and the N-N ligand lies in the basal plane. IR spectra and electrochemical analyses indicate that electron density at the iron centers decreases in the order 1 > 2 > 3 > 4. Furthermore, compound 2 undergoes a ligand-centered reduction at the same potential that the hexacarbonyl precursor undergoes its first reduction. However, unlike the 2,2-bipy derivatives 1 and 3, the 2,2-bpym complexes 2 and 4 are not effective catalysts for electrochemical proton reduction from acetic acid.