Highly Regio- and Stereoselective Hydrosilylation of Alkynes Catalyzed by Tridentate Cobalt Complexes.

Several cobalt complexes bearing tridentate (NNN) ligands were synthesized and served as precatalysts for alkyne hydrosilylation with Ph2 SiH2 . For terminal alkynes, the catalyst L2 b-CoCl2 was selected, and resulted in the corresponding α-vinylsilanes with high (Markovnikov) regioselectivity and extensive functional-group tolerance. For internal diaryl alkynes, the catalyst L2 c-CoCl2 exhibited the best activity, and afforded E-selective vinylsilanes through syn-addition in excellent yield under mild conditions.