Cobalt(I)-Catalyzed Transformation of Si-H Bonds: H/D Exchange in Hydrosilanes and Hydrosilylation of Olefins

Abstract

The amino imidazolin-2-imine ligand [HAmIm, 1,2-(DippNH)-C6H4-N═C(NiPrCMe)2] is employed in the synthesis of the paramagnetic cobalt(I) arene complex Co(AmIm)(η6-C6H6). The latter was found to be a highly efficient (pre)catalyst in H/D exchange reactions with deuterium (D2) in hydrosilanes. The scope comprises primary to tertiary silanes at a low catalyst loading of 1 mol %. Additionally, the same cobalt(I) arene complex was able to catalyze hydrosilylation reactions of terminal olefins with primary to tertiary silanes at low catalyst loadings of 0.5 mol %. The scope of hydrosilylation includes intramolecular hydrosilylation to produce silacarbocycles and multiple hydrosilylation with primary silanes. The mechanistic investigation includes numerous control experiments for both H/D exchange and hydrosilylation. Isolated (trapped) cobalt(III) hydride silyl complexes (including X-ray crystallographic authentication) are presented for primary to tertiary Si-H entities, which demonstrates a wide scope of Si-H bond activation by the low-valent Co(AmIm) core. The experimental results are strongly corroborated by density functional theory calculations, which explore the possible reaction mechanisms of studied reactions.