Ru‐Catalyzed Transfer Hydrogenation of Nitriles, Aromatics, Olefins, Alkynes and Esters
作者:Iryna D. Alshakova、Bulat Gabidullin、Georgii I. Nikonov
DOI:10.1002/cctc.201801039
日期:2018.11.7
preparation of new ruthenium(II) complexes supported by a pyrazole‐phosphine ligand and their application to transferhydrogenation of various substrates. These Ru complexes were found to be efficient catalysts for the reduction of nitriles and olefins. Heterocyclic compounds undergo transferhydrogenation with good to moderate yields, affording examples of unusual hydrogenation of all‐carbon‐rings
Substituent Control of Hydrogen Bonding in Palladium(II)−Pyrazole Complexes
作者:Douglas B. Grotjahn、Sang Van、David Combs、Daniel A. Lev、Christian Schneider、Christopher D. Incarvito、Kim-Chung Lam、Gene Rossi、Arnold L. Rheingold、Marc Rideout、Christoph Meyer、Genaro Hernandez、Lupe Mejorado
DOI:10.1021/ic026104n
日期:2003.5.1
Inter- and intramolecular hydrogen bonding of an N-H group in pyrazole complexes was studied using ligands with two different groups at pyrazole C-3 and C-5. At C-5, groups such as methyl, i-propyl, phenyl, or tert-butyl were present. At C-3, side chains L-CH2- and L-CH2CH2- (L = thioether or phosphine) ensured formation of chelates to a cis-dichloropalladium(II) fragment through side-chain atom L and the pyrazole nitrogen closest to the side chain. The significance of the ligands is that by placing a ligating side chain on a ring carbon (C-3), rather than on a ring nitrogen, the ring nitrogen not bound to the metal and its attached proton are available for hydrogen bonding. As desired, seven chelate complexes examined by X-ray diffraction all showed intramolecular hydrogen bonding between the pyrazole N-H and a chloride ligand in the cis position. In addition, however, intermolecular hydrogen bonding could be controlled by the substituent at C-5: complexes with either a methyl at C-5 or no substituent there showed significant intermolecular hydrogen bonding interactions, which were completely avoided by placing a tert-butyl group at C-5. The acidity of two complexes in acetonitrile solutions was estimated to be closer to that of pyridinium ion than those of imidazolium or triethylammonium ions.