Nickel Dithiolene Chelate Rings in a New Role as η⁵-Coordinating Ligands: Synthesis, Structural Characterization, and Redox Reactivity of an “Fe₂Ni” Bis-Double-Decker

A bis-double-decker complex has been assembled from the nickel bisdithiolene complex [Ni(S2C2Me2)2]1-/2- and two [Cp*Fe]+ units (Cp* = C5Me5). The complex, [(η5-Cp*-Fe-μ-η5,η5-((S2C2Me2)2Ni)Fe-η5-Cp*]n (1n), was isolated in two charge states (n = 0, 1). The structure of 1+ was confirmed by X-ray crystallography for 1+PF6− and 1+BF4−, and it shows the nickel bisdithiolene units π-donating to iron centers. Both salts crystallize in a centrosymmetric space group (center of inversion at nickel). Computational (density functional theory) data indicate a highly delocalized spin density for 1+. The reaction of 1 with 1 or 2 equiv of HBF4 leads to oxidation to form 1+ or 12+, respectively. On an electrochemical time scale, reversibility is observed for the redox series 1/1+/12+, with an additional slower step for oxidation of 12+.