lodsubstituierte Eisen-Schwefel-Cluster: Neue Synthesen sowie zur Bildung und Stabilität von Fe₂S₂I₄ ^2-, Fe₄S₄I₄ ^2– und Fe₆S₆I₆ ^2-. Die Kristallstruktur von (Et₄N)₆(Fe₄S₄l₄)₂Fe₂S₂l₄ / Iodine Substituted Iron-Sulfur-Clusters: Novel Syntheses, Formation and Stability of Fe₂S₂I₄ ^2-, Fe₄S₄I₄ ^2- und Fe₆S₆I₆ ^2-. The Crystal Structure of (Et₄N)₆(Fe₄S₄l₄)₂Fe₂S₂l₄

Abstract

Fe 4 S 4 I 4 2- has been prepared in tetrahydrofuran (THF) solution by the reaction of Fe, S 8 , I 2 , and Me 3 NCH 2 Ph + TI - , and isolated as black, fairly air-stable crystals of (Me 3 NCH 2 Ph) 2 Fe 4 S 4 I 4 (1) in nearly quantitative yield. 1 reacts with iron and iodine or with elemental sulfur and Fel 2 in CH 2 Cl 2 solution to form Fe 6 S 6 I 6 2- which was isolated as black crystals of (Me 3 NCH 2 Ph) 2 Fe 6 S 6 I 6 (5). In THF solution Fe 6 S 6 I 6 2- is converted to Fe 4 S 4 I 4 2- which was isolated as Fe(THF) 6 Fe 4 S 4 I 4 ·4 THF (3). Evidence is presented for an equilibrium between Fe 2 S 2 I 4 2- and Fe 4 S 4 I 4 2- , Fel 4 2- and sulfur when iron, sulfur, iodine and Et 4 N + I - react (with the required stoichiometry) to form Fe 2 S 2 I 4 2- in CH 2 Cl 2 solution. From this solution (Et 4 N) 6 (Fe 4 S 4 I 4 )2Fe 2 S 2 I 4 (6 ) crystallizes as black needles (tetragonal, P4 2 bc, a = 2467.9, b = 1653.8 pm, Z = 4). Crystals of 6 consist of the discrete anions Fe 4 S 4 I 4 2- and Fe 2 S 2 I 4 2- and Et 4 N + cations. The [Fe 4 S 4 ] 2+ core does not exhibit the usually observed core distortion. This clearly demonstrates that additional ligands (THF, CH 3 CN, iodide ions etc.) strongly reduce the stability of iodine substituted Fe/S clusters (except [Fe 4 S 4 ] 2+ cores!). The biological relevance of the observed rearrangements is discussed.