Highly Selective Hydroboration of Terminal Alkenes Catalyzed by a Cobalt Pincer Complex Featuring a Central Reactive N-Heterocyclic Phosphido Fragment

The application of a cobalt pincer complex, ((PPP)-P-Cl)CoCl2, as a precatalyst for the hydroboration of terminal alkenes with pinacolborane (HBPin) is described. The reactions proceed rapidly under mild conditions (room temperature, 30 min) with low catalyst loadings (1 mol %) using KBEt3H (2.1 mol %) as an activator to afford terminal hydroboration products with very high selectivity for the anti-Markovnikov product. The precatalyst is effective toward vinyl arenes and aliphatic alkenes and proceeds to an 83-98% yield with these substrates. However, the functional group tolerance of the catalytic system is somewhat limited, as minimal conversion is observed with internal olefins or when pyridine, ketone, or allyl ether functional groups are present. Deuterium labeling studies and spectroscopic identification of the catalyst deactivation product suggest a (PPP)CoH active species.

Automated summary

A cobalt pincer complex is utilized as a precatalyst for the hydroboration of terminal alkenes, displaying high selectivity with low catalyst loadings. However, the catalytic system shows limited tolerance towards certain functional groups.