Binuclear Oxidative Addition of Aryl Halides

Reaction of LCoCH2SiMe3(L= 2,6-bis[2,6-dimethyl-phenyliminoethyl]pyridine) with H-2 produces LCo(N-2), presumably via intermediate LCoH. Reaction of LCo(N-2) (prepared in this way or via reaction of LCoCl2 with Na/Hg) with aryl halides ArX (X = Cl, Br, I) produces LCoAr and LCoX in a ratio depending on the nature of Ar and X. For X = Cl, the reaction is slowest but also produces the largest amount of LCoAr. Electron-withdrawing substituents both accelerate the reaction and improve the yield of LCoAr. Computational studies support a radical mechanism for this reaction, involving displacement of N-2 to give LCo(XAr) followed by loss of the Ar radical, which then binds to a second Co(0) moiety.