Co-Catalyzed P–H Activation and Related Cp*Co(III) Phosphine Complexes

This study reports that the well-known Co(III) precursor Co(η⁵-Cp*)I₂(CO) (1) is an effective precatalyst for dehydrocoupling reactions of phosphines. Reaction monitoring by NMR, complemented by ESI-MS and EPR, suggests that Co(III) complexes containing secondary and primary phosphine ligands play an important role in this catalysis but that redox chemistry is also facile for these complexes, resulting in paramagnetic species. Representative examples of the mono(phosphine) complexes Co(η⁵-Cp*)I₂(PR₂H) (2) and Co(η⁵-Cp*)I₂(PRH₂) (4) and bis(phosphine) complexes [Co(η⁵-Cp*)I(PR₂H)₂] I (3) have been prepared. The characterization of these complexes through structural, computational, spectroscopic, and electrochemical analysis is reported and serves as a foundation for considering their mechanistic significance in the observed catalytic dehydrocoupling chemistry.