Preparation, structures and electrochemical property of phosphine substituted diiron azadithiolates relevant to the active site of Fe-only hydrogenases

Mono- and di-phosphine diiron azadithiolate complexes [{(mu-SCH2)(2)N(4-NO2C6H4)}Fe-2(CO)(5)(PMe3)] (2), [{(mu-SCH2)(2)N(4NO(2)C(6)H(4))} {Fe(CO)(2)L}(2)] (3, L = PMe3; 4, PMe2Ph) and the mu-hydride diiron complex [3(FeHFe)](+)[PF6](-) were prepared as biontimetic models of the active site of Fe-only hydrogenases. The complexes 2-4 and [3(FeHFe)](+)[PF6](-) were characterized by IR P-31, H-1 and C-13 NMR spectra and their molecular structures were determined by single crystal X-ray analyses. The PMe3 ligand in complex 2 lies on the basal position. The PMe3-disubstituted complex 3 exists as two configuration isomers, transoid basal/basal and apical/basal, in the crystalline state, while two PMe2Ph ligands of 4 are in an apical/basal orientation. The variable temperature P-31 NMR spectra of 2 and 3 were made to have an insight into the existence of the possible conformation isomers of 2 and 3 in solution. The [3(FeHFe)](+) cation possesses the sole transoid ba/ba geometry as other reported mu-hydride diiron analogues. The electrocatalytic property of {(mu-SCH2)(2)NC6H5}[Fe(CO)(2)PMe3](2) (5) was studied for proton reduction in the presence of HOAc. (c) 2006 Elsevier Inc. All rights reserved.