Crystal structure and spectroscopic and redox properties of the iron–sulphur cluster compound [NEt4]2[Fe4S4(SC6H4NH2-4)4]

Abstract

A 4Fe-ferrodoxin analogue involving functional thiolato-groups, [Fe₄S₄(SC₆H₄NH₂-4)₄]^2–, has been prepared and, as its [NEt₄]⁺ salt, characterised by X-ray crystallography, u.v.-visible, ¹H and ¹³C n.m.r. spectroscopy, and electrochemistry. The geometry of the Fe₄S₄ core is very similar to that previously established for other clusters of this type and possesses crystallographic S₄ symmetry; the Fe₄ tetrahedron is slightly compressed along the S₄ axis and the Fe ⋯ Fe edges group as four shorter [2.741(1)Å] and two longer [2.767(1)Å] distances. The NH₂ groups do not participate in any secondary bonding interactions. The complex undergoes two quasi-reversible, one-electron reductions at –1.12 and –1.74 V (vs. saturated calomel electrode).