A CoI-triphos complex (triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane) reacts at room temperature with p-toulenesulfonic acid monohydrate in acetonitrile to generate hydrogen (0.5 equivalents) and CoII with a driving force of just 30 meV/Co. Protonation of CoI produces a transient CoIII-H complex that has been characterized by nuclear magnetic resonance spectroscopy. The CoIII-H intermediate decays by second-order kinetics with an inverse dependence on acid concentration. Analysis of the kinetics suggests that CoIII-H produces hydrogen by a dominant heterolytic channel in which a highly reactive CoII-H transient is generated by CoI reduction of CoIII-H. The CoI-triphos complex also reacts with excess formic acid to produce H2 and CO2. The mechanism of this transformation has been probed electrochemically and in studies of the gas evolution kinetics.

Cobalt catalyzed hydrogen evolution and formic acid dehydrogenation

247th National Meeting (2014)

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