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).