15186-68-2Relevant academic research and scientific papers
Bimetallic C-C Bond-Forming Reductive Elimination from Nickel
Xu, Hongwei,Diccianni, Justin B.,Katigbak, Joseph,Hu, Chunhua,Zhang, Yingkai,Diao, Tianning
supporting information, p. 4779 - 4786 (2016/05/09)
Ni-catalyzed cross-coupling reactions have found important applications in organic synthesis. The fundamental characterization of the key steps in cross-coupling reactions, including C-C bond-forming reductive elimination, represents a significant challenge. Bimolecular pathways were invoked in early proposals, but the experimental evidence was limited. We present the preparation of well-defined (pyridine-pyrrolyl)Ni monomethyl and monophenyl complexes that allow the direct observation of bimolecular reductive elimination to generate ethane and biphenyl, respectively. The sp3-sp3 and sp2-sp2 couplings proceed via two distinct pathways. Oxidants promote the fast formation of Ni(III) from (pyridine-pyrrolyl)Ni-methyl, which dimerizes to afford a bimetallic Ni(III) intermediate. Our data are most consistent with the subsequent methyl coupling from the bimetallic Ni(III) to generate ethane as the rate-determining step. In contrast, the formation of biphenyl is facilitated by the coordination of a bidentate donor ligand.
Metal-vapor synthesis and electrochemistry of bis(bipyridyl)nickel(0)
Henne, Bruce J.,Bartak, Duane E.
, p. 369 - 373 (2008/10/08)
The preparation of bis(2,2′-bipyridyl)nickel (Ni(bpy)2) has been accomplished by the use of metal-vapor methods. A nickel-toluene matrix technique in which toluene-solvated nickel atoms were present as intermediates was employed. Electrochemical data for Ni(bpy)2 and tris(2,2′-bipyridyl)nickel(II) perchlorate (Ni(bpy)3(ClO4)2) in acetonitrile was obtained with cyclic voltammetric, chronoamperometric, and coulometric techniques. A total of five stable formal oxidation states for these nickel-2,2′-bipyridine complexes were observed: +3, +2, 0, -1, -2. A comparison of the reduction potentials of these complexes indicates that a significant portion of the electron density of the lower valence complexes (e.g., -1 and -2 oxidation states) resides on the bipyridyl ligand. An overall scheme for the electron-transfer pathways for nickel-2,2′-bipyridine complexes is proposed.
