Preparation, X-ray Structure, and Reactivity of an Osmium-Hydroxo Complex Stabilized by an N-Heterocyclic Carbene Ligand: A Base-Free Catalytic Precursor for Hydrogen Transfer from 2-Propanol to Aldehydes
Citations Over TimeTop 10% of 2008 papers
Abstract
Complex [(η6-p-cymene)OsCl(IPr)]OTf (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene; OTf = CF3SO3) reacts with NaOH to give [(η6-p-cymene)Os(OH)(IPr)]OTf (2), which under hydrogen atmosphere affords [(η6-p-cymene)OsH3(IPr)]OTf (3). The hydride ligands of 3 undergo exchange coupling, decreasing the H−H coupling constant from 206 to 74 Hz in the temperature range 213−178 K. Complex 3 is also obtained in a two-step procedure involving the reaction of 2 with NaBH4 to give (η6-p-cymene)OsH2(IPr) (4) and the protonation of the latter with HOTf. Attempts to obtain 4 directly from 1 or (η6-p-cymene)OsCl2(IPr) (5) are unsuccessful. In both reactions (η6-p-cymene)OsHCl(IPr) (6) is formed. Complex 2 also reacts with methanol and 2-propanol. At −30 °C, the reaction with the first of them leads to [(η6-p-cymene)Os(OMe)(IPr)]OTf (7), while with the second one, [(η6-p-cymene)OsH{κ1-OC(CH3)2}(IPr)]OTf (8) is obtained. Complex 2 is a catalyst precursor for the hydrogen transfer from 2-propanol to aldehydes, which does not need a base. The obtained TOF values are between 950 and 3500 h−1. The X-ray structures of 2 and 6 are also reported.
Related Papers
- → Synthesis and Characterization of Highly Water Soluble Ruthenium(II) and Osmium(II) Complexes Bearing Chelating Sulfonated N-Heterocyclic Carbene Ligands(2013)52 cited
- → Synthesis of Trinuclear Osmium Polyhydrido Clusters [{(C5Me5)Os}3(μ-H)6]+ and {(C5Me5)Os}3(μ-H)3(μ3-H)2 and Comparison with the Ruthenium Analogues(2008)16 cited
- → Contrasts in the chemistry of trinuclear cluster complexes of osmium and ruthenium. Formation of a fischer carbene or a functionalized μ3,η2-vinylidene group(1988)9 cited
- → Reactivity of new osmium dihydrides with arenediazonium cations: preparation and properties of bis(aryldiazene) and mono(aryldiazenido) complexes. A comparison with analogous iron and ruthenium derivatives(1989)25 cited
- → N-heterocyclic carbene and phosphine complexes of osmium and ruthenium carbonyls(2008)