Iron(I) and Iron(II) Amido-imidazolin-2-imine Complexes as Catalysts for H/D Exchange in Hydrosilanes

Abstract

The unsymmetrical amino-imidazolin-2-imine ligand [HAmIm, 1,2-(DippNH)-C6H4-N=C(NiPrCMe)2] is employed in the synthesis of the iron(I) arene complex [(AmIm)Fe(η6-C6H6)] and the iron(II) neosilyl complex [(AmIm)Fe(CH2SiMe3)]. These compounds are highly efficient precatalysts in H/D exchange reactions with deuterium (D2) in hydrosilanes. The scope comprises primary to tertiary silanes at a catalyst loading of 1 mol % at ambient temperature. In-depth mechanistic studies including various control experiments and the syntheses of isolated iron-hydride and iron-silyl compounds are performed. These studies reveal that the activation of both Fe(I) and Fe(II) complexes generates Fe-H/D species as key catalytic intermediates. An alternative catalytic pathway involving an iron-silyl intermediate, although shown to be less feasible by DFT calculations, may also be operative.