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 ((PDI)-P-iPr)FeX2 ((PDI)-P-iPr = ((2,6-CHMe2)(2)C6H3N=CMe)(2)C5H3N; X = Cl, Br) with sodium amalgam under 1 atm of dinitrogen afforded the square pyramidal, high spin iron(0) bis(dinitrogen) complex ((PDI)-P-iPr)Fe(N-2)(2). In solution, ((PDI)-P-iPr)Fe(N-2)(2) loses 1 equiv of N-2 to afford the mono(dinitrogen) adduct ((PDI)-P-iPr)Fe(N-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 (less than or equal to0.3 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) sigma-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.