Cleavage of Carbon−Carbon Bonds in Aromatic Nitriles Using Nickel(0)

• Published in: Journal of the American Chemical Society Vol. 124; no. 32; pp. 9547 - 9555
• Main Authors: Garcia, Juventino J, Brunkan, Nicole M, Jones, William D
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 14.08.2002
• Subjects: Chemistry; Exact sciences and technology; Kinetics and mechanisms; Organic chemistry; Reactivity and mechanisms; Substituent effect; Nickel Complexes; Nitrile; Nitrogen heterocycle; Organic ligand; Quinoline derivatives; Transition metal Complexes; Thermal reaction; Experimental study; Hydrido complex; Chemical activation; Carbon carbon bond; Addition reaction; Bicyclic compound; Reaction mechanism; Benzonitrile derivatives; Benzenic compound; Kinetic parameter; Rate constant
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0204933

The nickel(0) fragment [(dippe)Ni] has been found to react with a variety of aromatic nitriles. Initial π-coordination to the CC and C⋮N bonds of 2-cyanoquinoline is found to lead ultimately to C−CN oxidative addition. 3-Cyanoquinoline reacts similarly, although no η2-CN complex is observed. 2-, 3-, And 4-cyanopyridines react initially to give η2-nitrile complexes that then lead to quantitative formation of C−CN oxidative addition products. Benzonitrile reacts similarly but undergoes reversible insertion into the Ph−CN bond to give an equilibrium mixture of Ni(II) and Ni(0) adducts. A series of para-substituted benzonitriles has been studied in terms of both the position of the equilibrium between (dippe)Ni(η2-arylnitrile) ⇌ (dippe)Ni(CN)(aryl) and the rate of approach to equilibrium, and the Hammett plots indicate a buildup of negative charge at the ipso carbon both in the transition state and the Ni(II) product. Terephthalonitrile gives both η2-nitrile and oxidative addition adducts, as well as dimetalated products. No C−C or C−N cleavage of the aromatic ring is seen with quinoline or acridine; only η2-arene complexes are formed. The structures of many of these compounds are supported by X-ray data.