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, AsPh3 . Whereas using the dinuclear catalyst Mn2 (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.