Fe₄S₄I₄^2- has been prepared in tetrahydrofuran (THF) solution by the reaction of Fe, S₈, I₂, and Me₃NCH₂Ph⁺TI^-, and isolated as black, fairly air-stable crystals of (Me₃NCH₂Ph)₂Fe₄S₄I₄ (1) in nearly quantitative yield. 1 reacts with iron and iodine or with elemental sulfur and Fel₂ in CH₂Cl₂ solution to form Fe₆S₆I₆^2- which was isolated as black crystals of (Me₃NCH₂Ph)₂Fe₆S₆I₆ (5). In THF solution Fe₆S₆I₆^2- is converted to Fe₄S₄I₄^2- which was isolated as Fe(THF)₆Fe₄S₄I₄·4 THF (3). Evidence is presented for an equilibrium between Fe₂S₂I₄^2- and Fe₄S₄I₄^2-, Fel₄^2- and sulfur when iron, sulfur, iodine and Et₄N⁺I^- react (with the required stoichiometry) to form Fe₂S₂I₄^2- in CH₂Cl₂ solution. From this solution (Et₄N)₆(Fe₄S₄I₄)2Fe₂S₂I₄ (6 ) crystallizes as black needles (tetragonal, P4₂bc, a = 2467.9, b = 1653.8 pm, Z = 4). Crystals of 6 consist of the discrete anions Fe₄S₄I₄^2- and Fe₂S₂I₄^2- and Et₄N⁺ cations. The [Fe₄S₄]²⁺ core does not exhibit the usually observed core distortion.

This clearly demonstrates that additional ligands (THF, CH₃CN, iodide ions etc.) strongly reduce the stability of iodine substituted Fe/S clusters (except [Fe₄S₄]²⁺ cores!).

The biological relevance of the observed rearrangements is discussed.