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Article Dans Une Revue Journal of Organometallic Chemistry Année : 2007

Proton reduction catalysis by manganese vinylidene and allenylidene complexes

Résumé

The present paper reports the unprecedented observation of a catalytic electrochemical proton reduction based on metallocumulene complexes. Manganese phenylvinylidene (η5-C5H5)(CO)(PPh3)Mndouble bondCdouble bondC(H)Ph (1) and diphenylallenylidene (η5-C5H5)(CO)2Mndouble bondCdouble bondCdouble bondCPh2 (3) are shown to catalyze the reduction of protons from HBF4 into dihydrogen in CH2Cl2 or CH3CN media at −1.60 and −0.84 V (in CH3CN) vs. Fc, respectively. The working potential for 3 (−0.84 V vs. Fc in CH3CN) is the lowest reported to date for protonic acids reduction in non-aqueous media. The similar catalytic cycles disclosed here include the protonation of 1, 3 into the carbyne cations [(η5-C5H5)(CO)(PPh3)Mntriple bondC–CH2Ph]BF4 ([2]BF4), [(η5-C5H5)(CO)2Mntriple bondC–CHdouble bondCPh2]BF4 ([4]BF4) followed by their reduction to the corresponding 19-electron radicals 2radical dot, 4radical dot, respectively. Both carbyne radicals undergo a rapid homolytic cleavage of the Cβ–H bond generating an H-radical producing molecular hydrogen with concomitant recovery of the neutral metallocumulenes thereby completing a catalytic cycle.
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Dates et versions

hal-03739916 , version 1 (28-07-2022)

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Dmitry A. Valyaev, Mikhail Peterleitner, Oleg Semeikin, Kamil Utegenov, Nikolai Ustynyuk, et al.. Proton reduction catalysis by manganese vinylidene and allenylidene complexes. Journal of Organometallic Chemistry, 2007, 692 (15), pp.3207-3211. ⟨10.1016/j.jorganchem.2007.01.055⟩. ⟨hal-03739916⟩
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