Phosphine‐NHC Manganese Hydrogenation Catalyst Exhibiting a Non‐Classical Metal‐Ligand Cooperative H2 Activation Mode

• Published in: Angewandte Chemie 2019-05, Vol.131 (20), p.6799-6803
• Main Authors: Buhaibeh, Ruqaya, Filippov, Oleg A., Bruneau‐Voisine, Antoine, Willot, Jérémy, Duhayon, Carine, Valyaev, Dmitry A., Lugan, Noël, Canac, Yves, Sortais, Jean‐Baptiste
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts; Chemistry; DFT-Rechnungen; Hydrogenation; Ligands; Mangan; Manganese; Metall-Liganden-Kooperation; Metals; N-heterozyklische Carbene; Phosphine; Phosphoniumylide; Phosphorus; Reaction mechanisms
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201901169

Deprotonation of the MnI NHC‐phosphine complex fac‐[MnBr(CO)3(κ2P,C‐Ph2PCH2NHC)] (2) under a H2 atmosphere readily gives the hydride fac‐[MnH(CO)3(κ2P,C‐Ph2PCH2NHC)] (3) via the intermediacy of the highly reactive 18‐e NHC‐phosphinomethanide complex fac‐[Mn(CO)3(κ3P,C,C‐Ph2PCHNHC)] (6 a). DFT calculations revealed that the preferred reaction mechanism involves the unsaturated 16‐e mangana‐substituted phosphonium ylide complex fac‐[Mn(CO)3(κ2P,C‐Ph2P=CHNHC)] (6 b) as key intermediate able to activate H2 via a non‐classical mode of metal‐ligand cooperation implying a formal λ5‐P–λ3‐P phosphorus valence change. Complex 2 is shown to be one of the most efficient pre‐catalysts for ketone hydrogenation in the MnI series reported to date (TON up to 6200). Ein NHC‐Phosphin‐Mangan‐Komplex wird in Gegenwart einer Base in ein NHC‐Phosphinomethanid‐Derivat umgewandelt, das in der Lage ist, Wasserstoff über einen nicht‐klassischen Metall‐Liganden‐Kooperationsmodus zu aktivieren. Dieser Prozess ist für die Katalyse relevant, die eines der effizientesten Mn‐basierten Systeme zur Ketonhydrierung liefert.