Asymmetric Hydrogenation with Iridium C, N and N, P Ligand Complexes: Characterization of Dihydride Intermediates with a Coordinated Alkene1. (21st January 2014)

• Record Type: Journal Article
• Authors: Gruber, Stefan; Pfaltz, Andreas
• Is Part Of: Angewandte Chemie. Volume 126:Number 7(2014)
• Page Start: 1927
• Page End: 1931
• Publication Date: 2014-01-21
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201309515
• Languages: English
• ISSNs: 0044-8249

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Previously elusive iridium dihydride alkene complexes have been identified and characterized by NMR spectroscopy in solution. Reactivity studies demonstrated that these complexes are catalytically competent intermediates. Additional H₂ is required to convert the catalyst‐bound alkene into the hydrogenation product, supporting an Ir^III/Ir^V cycle via an [Ir^III(H)₂(alkene)(H₂)(L)]⁺ intermediate, as originally proposed based on DFT calculations. NMR analyses indicate a reaction pathway proceeding through rapidly equilibrating isomeric dihydride alkene intermediates with a subsequent slow enantioselectivity‐determining step. As in the classical example of asymmetric hydrogenation with rhodium diphosphine catalysts, it is a minor, less stable intermediate that is converted into the major product enantiomer.</p> </abstract>