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

Abstract

Mono- and di-phosphine diiron azadithiolate complexes [{(μ-SCH 2) 2N(4-NO 2C 6H 4)}Fe 2(CO) 5(PMe 3)] ( 2), [{(μ-SCH 2) 2N(4-NO 2C 6H 4)}{Fe(CO) 2L} 2] ( 3, L = PMe 3; 4, PMe 2Ph) and the μ-hydride diiron complex [ 3(FeHFe)] +[PF 6] − were prepared as biomimetic models of the active site of Fe-only hydrogenases. The complexes 2– 4 and [3(FeHFe)] +[PF 6] − were characterized by IR, 31P, 1H and 13C NMR spectra and their molecular structures were determined by single crystal X-ray analyses. The PMe 3 ligand in complex 2 lies on the basal position. The PMe 3-disubstituted complex 3 exists as two configuration isomers, transoid basal/basal and apical/basal, in the crystalline state, while two PMe 2Ph ligands of 4 are in an apical/basal orientation. The variable temperature 31P 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 μ-hydride diiron analogues. The electrocatalytic property of {(μ-SCH 2) 2NC 6H 5}[Fe(CO) 2PMe 3] 2 ( 5) was studied for proton reduction in the presence of HOAc.