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An Achiral Tetradentate Cis-α-Coordinating NCCN Ligand Gives Rise to a Configurationally Stable Chiral-at-Iron
Lukas Hinterlang1, Nemrud Demirel1, Sergei I Ivlev1
1Fachbereich Chemie, Philipps-Universität Marburg, Marburg, Germany.
Abstract:
Ligand design plays a crucial role in developing chiral transition metal complexes with enhanced or new catalytic properties. Here, we report our progress toward a new class of linear tetradentate NCCN ligands incorporating strongly σ-donating carbene moieties. The NCCN ligand coordinates to iron(II) in a cis-α topology, with two pyridine donors occupying the apical positions and two 1,2,3-triazolin-5-ylidene mesoionic carbene (MIC) donors in the equatorial plane. Two acetonitrile ligands complete the octahedral coordination sphere, and their lability provides the basis for the observed catalytic activity. Notably, the two strongly σ-donating MIC groups create a strong ligand field, which is critical for achieving configurational stability of the metal-centered stereogenicity. This design strategy thus enabled the first chiral-at-iron catalyst derived from an achiral tetradentate ligand, which was applied to catalytic and enantioselective C(sp3)-H amination and a Cannizzaro reaction.
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