Photoproduction of Hydrogen by Decamethylruthenocene Combined with Electrochemical Recycling.

The photoinduced hydrogen evolution reaction (HER) by decamethylruthenocene, Cp2 *RuII (Cp*=C5 Me5 ), is reported. The use of a metallocene to photoproduce hydrogen is presented as an alternative strategy to reduce protons without involving an additional photosensitizer. The mechanism was investigated by (spectro)electrochemical and spectroscopic (UV/Vis and 1 H NMR) measurements. The photoactivated hydride involved was characterized spectroscopically and the resulting [Cp2 *RuIII ]+ species was electrochemically regenerated in situ on a fluorinated tin oxide electrode surface. A promising internal quantum yield of 25 % was obtained. Optimal experimental conditions- especially the use of weakly coordinating solvent and counterions-are discussed.