Dichotomy of Manganese Catalysis via Organometallic or Radical Mechanism: Stereodivergent Hydrosilylation of Alkynes

Herein, we disclose the first manganese‐catalyzed hydrosilylation of alkynes featuring diverse selectivities. The highly selective formation of E ‐products was achieved by using mononuclear MnBr(CO) 5 with the arsenic ligand, AsPh 3 . Whereas using the dinuclear catalyst Mn 2 (CO) 10 and LPO (dilauroyl peroxide) enabled the reversed generation of Z ‐products in good to excellent stereo‐ and regioselectivity. Such a way of controlling the reaction stereoselectivity is unprecedented. Mechanistic experiments revealed the dichotomy of manganese catalysis via organometallic and radical pathways operating in the E ‐ and Z ‐selective routes, respectively.