Cyclic voltammetry has been used to investigate the reactions which the electrogenerated nickel(0) complex [Ni(pph3)4] undergoes in the presence of 1,2-dibromobenzene. It has been found that nickel(0) undergoes oxidative addition by o-C4H4Br2 leading to the σ-bonded organometallic derivative (NiII(PPh3)2 (o-C6H4Br)Br] which can be easily separated thanks to its low solubility in the employed solvent (CH3CN). Anyhow, the carbon-halogen bond present in the coordinated aromatic ring makes possible the reaction of this product with an excess of nickel (0), if present, to give an unstable species which decomposes yielding nickel(I) as the ultimate product. The mechanism operative in the electrochemical reduction of the organometallic nickel(II) product has been also studied. It allows an unusual dinickel heterocyclic species to be obtained through an electrochemical pathway involving a disproportionation reaction triggered by an irreversible chemical step. The occurrence of such a mechanism, which is consistent with all the reported data, has been also checked by employing the finite difference simulation procedure, together with the simplex fitting of the voltammetric curves. In this way, both the thermodynamic and the kinetic parameters characterizing the cathodic process have been obtained. © 1982.
An Electroanalytical investigation on carbon-nickel bonds formation. Evidence for an electrochemical process affording a dinickel heterocycle compound
DANIELE, Salvatore
1982-01-01
Abstract
Cyclic voltammetry has been used to investigate the reactions which the electrogenerated nickel(0) complex [Ni(pph3)4] undergoes in the presence of 1,2-dibromobenzene. It has been found that nickel(0) undergoes oxidative addition by o-C4H4Br2 leading to the σ-bonded organometallic derivative (NiII(PPh3)2 (o-C6H4Br)Br] which can be easily separated thanks to its low solubility in the employed solvent (CH3CN). Anyhow, the carbon-halogen bond present in the coordinated aromatic ring makes possible the reaction of this product with an excess of nickel (0), if present, to give an unstable species which decomposes yielding nickel(I) as the ultimate product. The mechanism operative in the electrochemical reduction of the organometallic nickel(II) product has been also studied. It allows an unusual dinickel heterocyclic species to be obtained through an electrochemical pathway involving a disproportionation reaction triggered by an irreversible chemical step. The occurrence of such a mechanism, which is consistent with all the reported data, has been also checked by employing the finite difference simulation procedure, together with the simplex fitting of the voltammetric curves. In this way, both the thermodynamic and the kinetic parameters characterizing the cathodic process have been obtained. © 1982.
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