om4007467_si_001.pdf (3.03 MB)
Download file

Characterization and Reactivity Studies of Dinuclear Iridium Hydride Complexes Prepared from Iridium Catalysts with N,P and C,N Ligands under Hydrogenation Conditions

Download (3.03 MB)
journal contribution
posted on 19.02.2016, 00:04 authored by Stefan Gruber, Markus Neuburger, Andreas Pfaltz
The dinuclear iridium hydride complexes [IrH­(CH3CN)­(L1)­(μ-H)]2­(BArF)2 (7; L1 = (S)-2-(2-((di­phenyl­phos­phanyl)­oxy)­propan-2-yl)-4-isopropyl-4,5-dihydrooxazole, BArF = tetrakis­[3,5-bis­(tri­fluoro­methyl)­phenyl]­borate), [IrH­(CH2Cl2)­(L1)­(μ-H)]2­(BArF)2 (8), [IrH­(L2)­(μ-H)]2­(BArF)2 (9a; L2 = (S)-1-[2-(2-adamantan-2-yl-4,5-dihydro­oxazol-4-yl)-ethyl]-3-(2,6-diiso­propyl­phenyl)-1,2-dihydroimidazol-2-ylidene), and [IrH­(L3)­(μ-H)]2­(BArF)2 (9b; L3 = (S)-1-[2-(2-tert-butyl-4,5-dihydrooxazol-4-yl)-ethyl]-3-(2,6-diiso­propyl­phenyl)-1,2-dihydro­imidazol-2-ylidene) were prepared from the corresponding mononuclear [Ir­(COD)­(L)]­BArF precursors by treatment with H2 and characterized by 2D NMR spectroscopy and X-ray diffraction. Conversion to a trinuclear iridium hydride complex, which is usually observed for N,P iridium hydride complexes, is inhibited by addition of 0.5 equiv of [H­(OEt2)2]­BArF or acetonitrile. Reactions with acetonitrile or 6,6′-bi-2-picoline afforded the mononuclear iridium dihydride complexes [Ir­(H)2­(CH3­CN)2­(L1)]­BArF (5), [Ir­(H)2­(CH3­CN)2­(L3)]­BArF (10), or [Ir­(H)2­(6,6′-bi-2-picoline)­(L3)]­BArF (11). The CH3CN complexes 7 and 10 are inactive as hydrogenation catalysts. In contrast, the coordinatively unsaturated dinuclear complexes 9a and 9b are active catalysts for the hydrogenation of (E)-1,2-diphenyl-1-propene at 50 bar hydrogen pressure.

History