Protonatium Equilibrium and Hydrogen Production by a Dinuclear Cobalt-Hydride Complex Reduced by Cobaltocene with Trifluoroacetic Acid

A dinuclear Co complex with bis(pyridyl)pyrazolato (bpp^–) and terpyridine (trpy) ligands, [Co^III₂(trpy)₂(μ-bpp)(OH)(OH₂)]⁴⁺ (1⁴⁺), undergoes three-electron reduction by cobaltocene in acetonitrile to produce 1⁺, which is in the protonation equilibrium with the Co^IICo^III–hydride complex, and the further protonation of the hydride by trifluoroacetic acid yields hydrogen quantitatively. The kinetic study together with the detection of the Co^IICo^III-hydride complex revealed the mechanism of the hydrogen production by the reaction of 1⁺ with trifluoroacetic acid.