Catalyse par des complexs σ-aryl-nickel de l'electroreduction en biaryles des halogenures aromatiques

In mixed THF/HPMA, electrochemical reduction of NiX₂L₂ (L = PPh₃, X = Cl or Br) yields a zerovalent nickel complex which reacts very rapidly with ArX (X = I, Br, Cl) by oxidative addition to give ArNiXL₂, which also is electroreducible. Thus it is possible to obtain a catalytic electroreduction of ArX which affords mainly biaryls when X = Cl. A mechanism is suggested according the various results especially with a view to explain the loss of catalytic activity. A clear indication of increasing activity is given when aliphatic bromides are added to the solutions.