Single protonation labilises but double protonation inhibits substitution of [Fe4S4Cl4]2−

Successive protonation of [Fe4S4(SPh)4]2– progressively labilises the cluster towards substitution of the thiolate ligands, whereas single protonation of [Fe4S4Cl4]2– catalyses, but diprotonation inhibits, substitution of the chloro-ligands.