Electrochemical Reactions of Dihalobis(isocyanide)nickel(II) at Platinum and Mercury Electrodes

Article abstract of DOI:10.1246/bcsj.66.778

Electrochemical reactions of divalent nickel complexes, NiX2(RNC)2 (1) (X=I, Br, Cl; R=2,6-Me2C6H3 (Xyl), 4-Br-2,6-Me2C6H2, 2,4-t-Bu2-6-MeC6H2, 2,4,6-t-Bu3C6H2) were carried out at Hg and Pt electrodes.Cyclic voltammograms (CVs) of 1 at a Pt electrode showed a quasi-reversible redox wave at ca. -0.50 V, due to two-electron reduction .The reduction potential of the iodide (1a) or bromide (1f) complex (R=Xyl) shifted to the positive side by ca. 0.3 V in the presence of isocyanide, due to the electrochemical reaction of NiX2(RNC)3 (X=I, Br).The chloride complex (1e) showed a similar potential in the presence in the presence or absence of isocyanide; there exists no five-coordinated complex.The CV of 1a at a Hg electrode showed a redox wave at -0.74 V, due to the redox reaction of the unsaturated species, (4) formed from the reaction of 1a with Hg, suggesting the CE mechanism.Compound 1a had a redox potential at -0.72 V in the presence of 2,6-xylyl isocyanide, being responsible for 2.The bromide complex showed a similar behavior, but the chloride complex underwent a very complicated reaction.The electrochemical mechanism of NiX2(RNC)2 with or without isocyanide is discussed.