Preparation and molecular and electronic structures of iron(0) dinitrogen and silane complexes and their application to catalytic hydrogenation and hydrosilation

Reduction of the five-coordinate iron(II) dihalide complexes ( ^iPrPDI)FeX₂ (^iPrPDI = ((2,6-CHMe ₂)₂C₆H₃N=CMe)₂C ₅H₃N; X = Cl, Br) with sodium amalgam under 1 atm of dinitrogen afforded the square pyramidal, high spin iron(0) bis(dinitrogen) complex (^iPrPDI)Fe(N₂)₂. In solution, ( ^iPrPDI)Fe(N₂)₂ loses 1 equiv of N₂ to afford the mono(dinitrogen) adduct (^iPrPDI)Fe(N₂) ₂. Both dinitrogen compounds serve as effective precatalysts for the hydrogenation and hydrosilation of olefins and alkynes. Effecient catalytic reactions are observed with low catalyst loadings (≤0.3 mol %) at ambient temperature in nonpolar media. The catalytic hydrosilations are selective in forming the anti-Markovnikov product. Structural characterization of a high spin iron(0) alkyne and a bis(silane) σ-complex has also been accomplished and in combination with isotopic labeling studies provides insight into the mechanism of both catalytic C-H and catalytic C-Si bond formation.