Synthesis, Characterization, and Alkyne Trimerization Catalysis of a Heteroleptic Two-Coordinate Fe^I Complex

The synthesis of the first heteroleptic, two-coordinate Fe^I complex IPr–Fe–N­(SiMe₃)­DIPP (1) (IPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazol-2-ylidene; DIPP = 2,6-ⁱPr₂–C₆H₃) is reported. Protonation of the Fe^II bis­(amido) complex Fe­[N­(SiMe₃)­DIPP]₂ followed by addition of IPr and reduction by potassium graphite in a one-pot reaction results in good yields of 1. The redox activity of 1 and comparison between 1 and its reduction product by ⁵⁷Fe Mössbauer spectroscopy are discussed, and the reduction was found to be metal-based rather than ligand-based. The activity of 1 toward the catalytic cyclotrimerization of terminal and internal alkynes is described.