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

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-(i)Pr2-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 (57)Fe 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.