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.