Cobalt-Catalyzed C–H Borylation

A family of pincer-ligated cobalt complexes has been synthesized and are active for the catalytic C−H borylation of heterocycles and arenes. The cobalt catalysts operate with high activity and under mild conditions and do not require excess borane reagents. Up to 5000 turnovers for methyl furan-2-carboxylate have been observed at ambient temperature with 0.02 mol % catalyst loadings. A catalytic cycle that relies on a cobalt­(I)–(III) redox couple is proposed.