460343-47-9Relevant academic research and scientific papers
C-CN bond activation of aromatic nitriles and fluxionality of the η2-arene intermediates: Experimental and theoretical investigations
Li, Ting,Garcia, Juventino J.,Brennessel, William W.,Jones, William D.
, p. 2430 - 2445 (2010/08/04)
[Ni(dippe)H]2 has been reacted with a variety of aromatic nitriles. Both experimental and DFT calculation results have shown that an η2-arene complex with nickel coordinated to the C=C double bond next to the cyano substituent is the crucial intermediate leading to C-CN bond activation. Furthermore, the fluxional processes of the η2-arene species were investigated by low-temperature experiments as well as computational methods. In the case of dicyanobenzenes, a mechanism similar to that found for PhCN was found with the Ni(dippe) fragment rotating as it migrated around the phenyl ring through a series of η3-allyl-like transition states. For polycyclic aromatic nitriles, only certain η2-arenes were stable enough to contribute to the fluxional process, and nickel migrates via an η4-coordinated transition state. The transition states connecting the η2-nitrile complex to the η2-arene intermediate and the η2-arene intermediate to the C-CN bond activation products are at much higher energies compared to those for migration around the ring. In the reaction of 9-cyanoanthracene, the instability of the η2-arene precursor and the high-energy activation barrier resulted in the absence of the C-CN oxidative addition product. The complex with 9-cyanophenanthrene undergoes only C-CN cleavage upon photolysis.
Cleavage of carbon-carbon bonds in aromatic nitriles using nickel(0)
Garcia, Juventino J.,Brunkan, Nicole M.,Jones, William D.
, p. 9547 - 9555 (2007/10/03)
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 CN 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.
