Earth-Abundant Metal Catalysis Enabled by Counterion Activation.

A precatalyst activation strategy has been developed for earth-abundant metal catalysis enabled by counterion dissociation and demonstrated through alkene hydroboration. Commercially available iron and cobalt tetrafluoroborate salts were found to catalyze the hydroboration of aryl and alkyl alkenes with good functional group tolerance (Fe, 12 substrates; Co, 13 substrates) with three structurally distinct ligands. Key to this endogenous activation was counterion dissociation to generate fluoride which indirectly activates the precatalyst by reaction with pinacol borane.