Single-Step Access to Thiolate-Supported, Six-Iron Clusters with an Authentic Carbide: Synthesis of [Fe₆(μ₆-C)(μ₂-Stol)(μ₂-CO)₂(CO)₁₂]³ via Non-PSEPT, Redox Intermediates

We report a general synthetic method to access iron–carbide(carbonyl) clusters ligated by thiolate. We previously established that multiple neutral ligand substitution (phosphine) was enabled by utilizing the conventional six–iron carbide cluster [Fe6(μ6–C)(μ2–CO)4(CO)12]2– and generating the 2 e– oxidized, polyhedral skeletal electron pair theory (PSEPT) non–compliant cluster [Fe6(μ6–C)(μ2–CO)4(CO)12]0. However, ligation of thiolate proved intractable via this route due to inherent thiolate-cluster redox processes, resulting simply in reformation of the dianionic cluster. Here, we extend the non–PSEPT in situ oxidation method by commencing with the "super–reduced" cluster [Fe6(μ6–C)(μ2–CO)4(CO)11]4– (2, [Bortoluzzi, M. Eur. J. Inorg. Chem. 2017, 2017(25), 3135–3143]): in situ oxidation of 2 generates the six–iron, non–PSEPT 84 e– anionic intermediate [Fe6(μ6–C)(μ2–CO)4(CO)11]2– (3) that is redox inactive with thiolates but substitutionally active. By this method, we synthesized the novel phosphine–bound cluster (4) [Fe6((μ6–C)PMe3(μ2–CO)4CO)11]2– and the novel thiolate–bound, intact six–iron carbide cluster [Fe6(μ6–C)(μ2–Stol)(μ2–CO)2(CO)11]3– (5). A further synthetic route to 5 is achieved by the reduction of [Fe5(μ5–C)(μ2–Stol)(CO)13]− (1) in the presence of Fe(CO)5, or rather with Na2[Fe(CO)4]. This synthetic method expands the scope to functionalize iron-carbide(carbonyl) with biorelevant ligands.