Redox behaviour of 4Fe-4S ferredoxin model arenethiolate complexes involving specific NH ⋯ S hydrogen bonds assisted by a neighbouring phenyl group

Abstract

The complexes [NMe₄]₂[Fe₄S₄(SC₆H₃Ph-6-NHCOR′-2)₄]^2–(R′= Bu^t1, Me 2 or CF₃3), [NMe₄]₂[Fe₄S₄(SC₆H₃Ph-6-NHCOR′-4)₄]^2–(R′= Bu^t4 or CF₃5) and [NMe₄]₂[Fe₄S₄(SC₆H₃Et-6-NHCOBu^t-2)₄]^2–6 were synthesized by ligand-exchange reactions of [NMe₄]₂[Fe₄S₄(SBu^t)₄]^2– with the corresponding organic disulfides. They have been characterized by IR and UV/VIS spectroscopy and by elemental microanalyses. From IR spectra in the solid state, the v(NH) shift (114 cm^–1) of 1 from the band of the corresponding disulfide is larger than that of 6(87 cm^–1). The results indicate that the phenyl group at the 6 position contributes to the strengthening of the NH ⋯ S hydrogen bond. The stabilization of the [Fe₄S₄(SR)₄]^––[Fe₄S₄(SR)₄]^2– redox potential of 1 compared with 6 is due to the co-operation of the aromatic ring and this hydrogen bond.