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Mechanistic study of the photo-generation of hydrogen by decamethylruthenocene
Date
2019
Abstract
Detailed studies on hydrogen evolution by decamethylruthenocene ([Cp*2RuII]) highlighted that metallocenes are capable of photoreducing hydrogen without the need for an additional sensitizer. Electrochemical, gas chromatographic, and spectroscopic (UV/Vis, 1H and 13C NMR) measurements corroborated by DFT calculations indicated that the production of hydrogen occurs by a two‐step process. First, decamethylruthenocene hydride [Cp*2RuIV(H)]+ is formed in the presence of an organic acid. Subsequently, [Cp*2RuIV(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*2RuIII]+ is further reduced with a second release of hydrogen by deprotonation of a methyl group of [Cp*2RuIII]+. Experimental and computational data show spontaneous conversion of [Cp*2RuII] to [Cp*2RuIV(H)]+ in the presence of protons. Calculations highlight that the first reduction is endergonic (ΔG0=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*2RuII] was also considered.
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Description
peer-reviewed
Publisher
John Wiley & Sons, Inc.
Citation
Chemistry: A European Journal;25 (55), pp. 12769-12779
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Funding Information
Swiss National Science Foundation