C–H Borylation of Arylsilane Catalyzed by an Iron Amido Complex

The selective functionalization of C–H bonds over reactive Si–H bonds in hydrosilanes is a challenge in synthetic chemistry. We report the synthesis and characterization of a four-coordinate, high-spin ( S = 2) iron amido complex bearing a PNN pincer ligand. The complex adopts a structure wherein one amido group coordinates to the iron center while the other binds to the ligand’s quinoline moiety. As a catalyst, this complex promotes the meta- and para- C–H borylation of dimethylphenylsilane. While both C–H and Si–H borylated products were observed at the early stage of the reaction, the Si–H borylated species was subsequently consumed, leading to an increase in the amount of C–H borylated products after 20 h. Mechanistic investigations, including control experiments and DFT calculations, suggest a pathway involving an in situ -generated silylborane intermediate. This transient species is consumed in the thermodynamically favorable C–H borylation step, accounting for the observed selectivity. This work describes a catalytic system that achieves the chemoselective functionalization of arylsilanes by channeling the reactive intermediate silylborane into C–H borylated products.