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Mechanistic Study on the Photogeneration of Hydrogen by Decamethylruthenocene
Author(s) -
Rivier Lucie,
Peljo Pekka,
Maye Sunny,
Méndez Manuel A.,
Vrubel Heron,
Vannay Laurent A. C.,
Corminboeuf Clémence,
Scanlon Micheál D.,
Girault Hubert H.
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201902353
Subject(s) - heterolysis , chemistry , deprotonation , hydride , hydrogen , ion , photochemistry , electrochemistry , medicinal chemistry , inorganic chemistry , catalysis , organic chemistry , electrode
Detailed studies on hydrogen evolution by decamethylruthenocene ([Cp* 2 Ru II ]) highlighted that metallocenes are capable of photoreducing hydrogen without the need for an additional sensitizer. Electrochemical, gas chromatographic, and spectroscopic (UV/Vis, 1 H and 13 C NMR) measurements corroborated by DFT calculations indicated that the production of hydrogen occurs by a two‐step process. First, decamethylruthenocene hydride [Cp* 2 Ru IV (H)] + is formed in the presence of an organic acid. Subsequently, [Cp* 2 Ru IV (H)] + is reversibly reduced in a heterolytic reaction with one‐photon excitation leading to a first release of hydrogen. Thereafter, the resultant decamethylruthenocenium ion [Cp* 2 Ru III ] + is further reduced with a second release of hydrogen by deprotonation of a methyl group of [Cp* 2 Ru III ] + . Experimental and computational data show spontaneous conversion of [Cp* 2 Ru II ] to [Cp* 2 Ru IV (H)] + in the presence of protons. Calculations highlight that the first reduction is endergonic (Δ G 0 =108 kJ mol −1 ) and needs an input of energy by light for the reaction to occur. The hydricity of the methyl protons of [Cp* 2 Ru II ] was also considered.