KoenigChemistry (@chemistrykoenig.bsky.social)

News from Manganese! Congratulations to Rohan who published with his former group @pubs.acs.org Photoexcited Manganese Complex of Abnormal N-Heterocyclic Carbene in Molecular Hydrogen Activation via Hydrogen Atom Transfer Pathway #ChemSky pubs.acs.org/doi/10.1021/...

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Photoexcited Manganese Complex of Abnormal N-Heterocyclic Carbene in Molecular Hydrogen Activation via Hydrogen Atom Transfer Pathway In this work, we show that the innate reactivity of the photoexcited state of a Mn-hydride complex can be harnessed to design the activation of the H2 molecule for catalytic applications. Such activation of molecular hydrogen by a photoexcited heavier 5d metal (Ir) complex has recently been achieved; however, it has been realized with an earth-abundant and lighter 3d metal complex. Here, we demonstrate that an in situ-generated Mn–H complex of an abnormal N-heterocyclic carbene can activate molecular hydrogen upon photoexcitation. The key to this approach lies in the fact that ground-state manganese hydride absorbs light to undergo homolytic cleavage, generating a metalloradical (Mn·) and a hydrogen atom. This, in turn, enables the formation of an O–H bond upon reaction with an aldehyde. Simultaneously, the generated Mn· can activate the H2 molecule, reproducing the Mn–H species in its ground state along with a hydrogen atom. The trapping of important intermediates, such as Mn· species and associated radical intermediates, using spectroscopic techniques confirms the mechanistic proposal involving the excited state of the Mn complex. https://pubs.acs.org/doi/10.1021/acscatal.5c06418