Co‐catalyzed Selective syn‐Hydrosilylation of Internal Alkynes

Vinylsilanes are highly appealing and convenient chemical derivatives, as evidenced by the increasing number of synthetic transformations utilizing this class of compounds. Herein, a new comprehensive cobalt‐catalyzed procedure has been developed enabling selective hydrosilylation of internal aryl‐, alkyl‐, and silylalkynes. Cobalt complexes bearing triazine‐based PNP pincer‐type ligands provide exclusive syn‐addition of primary as well as secondary silanes to C≡C bonds. As a result, (E)‐silylalkenes and vicinal disilylalkenes were effectively obtained with excellent stereoselectivity and regioselectivity. Unlike several TM‐catalyzed procedures, no external additives were required since hydrosilanes act as both substrates and activators. A new approach for syn‐selective hydrosilylation of internal alkynes was developed in the presence of cobalt complexes bearing triazine‐based PNP pincer‐type ligands. As a result, various vinylsilanes including vicinal disilylalkenes were efficiently obtained under mild conditions. The remarkable dual role of hydrosilanes as reagents and activators minimizes the utilization of external additives and increases the sustainability of the process.