Protonation 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(III)2(trpy)2(μ-bpp)(OH)(OH2)](4+) (1(4+)), undergoes three-electron reduction by cobaltocene in acetonitrile to produce 1(+), which is in the protonation equilibrium with the Co(II)Co(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(II)Co(III)-hydride complex revealed the mechanism of the hydrogen production by the reaction of 1(+) with trifluoroacetic acid.