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Zirconium-Catalyzed Imine Hydrogenation via a Frustrated Lewis Pair Mechanism

Research paper by Stephanie R. Flynn, Owen J. Metters, Ian Manners, Duncan F. Wass

Indexed on: 09 Mar '16Published on: 08 Mar '16Published in: Organometallics



Abstract

Zirconium-based frustrated Lewis pairs (FLPs) are active imine hydrogenation catalysts under mild conditions. Complexes of the type [CpR2ZrOMes][B(C6F5)4] utilize the imine substrate itself as the Lewis base component of the FLP. Catalyst performance is a function of ligand structure; in general more bulky, more electron rich cyclopentadienyl derivatives give the best results. However, Cp* derivatives are not catalytically active, being stable after initial heterolytic cleavage of H2; this allows experimental verification of the competence of the zirconocene–imine pair in FLP-type heterolytic H2 cleavage. Enamines and protected nitriles are also hydrogenated if an additional internal phosphine base is used.

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