Stepwise Reduction of Four Carbonyl Ligands in (η⁵-C₅H₄Me)₄Fe₄(μ₃-CO)₄ To Produce Clusters Containing μ₃-Methylidyne and/or Acetylene Ligands

Abstract

Treatment of (η5-C5H4Me)4Fe4(μ3-CO)4 with LiAlH4, followed by air-oxidation in the presence of NH4PF6, led to stepwise reduction of the four carbonyl ligands to afford [(η5-C5H4Me)4Fe4(μ3-CO)3(μ3-CH)](PF6), [(η5-C5H4Me)4Fe4(μ3-CO)2(μ3-CH)2](PF6)2, [(η5-C5H4Me)4Fe4(μ3-CO)(μ3-CH)(HCCH)](PF6), and [(η5-C5H4Me)4Fe4(HCCH)2](PF6). Two-electron reduction of [(η5-C5H4Me)4Fe4(μ3-CO)2(μ3-CH)2](PF6)2 resulted in coupling of two methylidyne ligands to form the acetylene-coordinated cluster (η5-C5H4Me)4Fe4(μ3-CO)2(HCCH), two-electron oxidation of which regenerated [(η5-C5H4Me)4Fe4(μ3-CO)2(μ3-CH)2](PF6)2. Further treatment of isolated (η5-C5H4Me)4Fe4(μ3-CO)2(HCCH) with LiAlH4 produced (η5-C5H4Me)4Fe4(HCCH)2. All clusters were fully characterized by X-ray diffraction studies.