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Phosphine Coordination to a Cobalt Diimine–Dioxime Catalyst Increases Stability during Light-Driven H2 Production

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posted on 20.02.2012, 00:00 by Pan Zhang, Pierre-André Jacques, Murielle Chavarot-Kerlidou, Mei Wang, Licheng Sun, Marc Fontecave, Vincent Artero
The combination of cobalt diimine–dioxime complexes with a cyclometalated iridium photosensitizer gives efficient systems for hydrogen generation under visible-light irradiation using triethylamine as a sacrificial electron donor. Interestingly, the addition of triphenylphosphine (PPh3) to the medium results in a significant improvement of the stability of the system, with up to ∼700 turnovers achieved within 10 h. UV–visible spectroscopic monitoring of the reaction allows identification of a PPh3-coordinated CoI intermediate as the active species. Mechanistic issues regarding (i) the photogeneration of the CoI species, (ii) the nature of the active species, and (iii) the influence of PPh3 on the H2-evolution mechanism are discussed.

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