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

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.