A Combined Experimental and Computational Study of Dihydrido(phosphinooxazoline)iridium Complexes

• Published in: Journal of the American Chemical Society Vol. 126; no. 43; pp. 14176 - 14181
• Main Authors: Mazet, Clément, Smidt, Sebastian P, Meuwly, Markus, Pfaltz, Andreas
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 03.11.2004
• Subjects: Chemistry; Exact sciences and technology; Inorganic chemistry and origins of life; Kinetics and mechanism of reactions; Cationic complex; Tertiary phosphine; Organic ligand; Theoretical study; NMR spectrometry; Transition metal Complexes; Experimental study; Iridium Complexes; Hydrido complex; Complexes Mixed; Density functional method; Platinoid Complexes; Ab initio calculations; Chemical reactivity
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja046318z

The reaction of a [(PHOX)Ir(COD)]+ complex (COD = 1,5-cyclooctadiene) with dihydrogen was studied by NMR spectroscopy (PHOX = chiral phosphinooxazoline ligand). A single [(PHOX)Ir(H)2(COD)]+ isomer was formed as the primary product at −40 °C in THF. Subsequent reaction with H2 at −40 to 0 °C led to a mixture of two diastereomeric [(PHOX)Ir(H)2(solvent)2]+ complexes with concomitant loss of cyclooctane. The stereochemistry of the three hydride complexes could be assigned from the NMR data. The structures and energies of the observed hydride complexes and the possible stereoisomers were calculated using density functional theory. The substantial energy differences (up to 39 kcal/mol) between the various stereoisomers demonstrate the strong influence of the chiral ligand. The observed stereoselective formation of dihydride complexes can be explained by steric effects of the PHOX ligand combined with a strong electronic influence of the coordinating N and P atoms, favoring addition of a hydride trans to the Ir−N bond.