Efficient and selective hydroboration of alkenes catalyzed by an air-stable (PP^CF3P)CoI₂ precatalyst

Alkene hydroboration provides a convenient route to generate organoborane synthons and recent efforts to develop catalysts for this and many other organic transformations have involved a shift to Earth-abundant first row transition metals. Herein, we report the synthesis of a new bench-stable Coⁱⁱ precatalyst, (PP^CF3P)CoI₂ (1), which was found to function as a highly active alkene hydroboration catalyst in the presence of an activator. The substrate scope was probed through exploring a collection of electronically and sterically distinct alkenes with a wide range of substitution patterns and functional groups. A single species is spectroscopically observed during catalysis, and activation of the Coⁱⁱ precatalyst with KBEt₃H in the presence of styrene and in the absence of HBpin affords this species, (PP^CF3P)Co(η²-styrene)H (2), which has been isolated, characterized, and demonstrated to function as an active catalyst for alkene hydroboration in the absence of additional activators. A plausible mechanism involving a Co^I-hydride active species is proposed based on catalytic and stoichiometric experiments.