Browsing by Subject "Nickel compounds"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    FTIR spectroscopic study on nickel(II)-exchanged sulfated alumina: nature of the active sites in the catalytic oligomerization of ethene
    (Springer, 2002) Davydov, A. A.; Kantcheva, M.; Chepotko, M. L.
    The nature of the active sites in nickel(II)-exchanged sulfated alumina in the reaction of ethene oligomerization has been studied by means of FTIR spectroscopy of adsorbed CO. It has been established that isolated nickel(I) species are the active sites in this process. These sites are formed by a reduction process, in which protonic centers are involved. The latter are due to the presence of covalently-bonded sulfate ions on the catalyst surface.
  • Thumbnail Image
    ItemOpen Access
    Spectroelectrochemistry of potassium ethylxanthate, bis(ethylxanthato)nickel(II) and tetraethylammonium tris(ethylxanthato)-nickelate(II)
    (Royal Society of Chemistry, 2001) Dag, Ö.; Yaman, S. Ö.; Önal, A. M.; Isci, H.
    Electrochemical and chemical oxidation of S2COEt−, Ni(S2COEt)2, and [Ni(S2COEt)3]− have been studied by CVand in situ UV-VIS spectroscopy in acetonitrile. Cyclic voltammograms of S2COEt− and Ni(S2COEt)2 display one (0.00 V) and two (0.35 and 0.80 V) irreversible oxidation peaks, respectively, referenced to an Ag/Ag+ (0.10 M) electrode. However, the cyclic voltammogram of [Ni(S2COEt)3]− displays one reversible (−0.15 V) and two irreversible (0.35, 0.80 V) oxidation peaks, referenced to an Ag/Ag+ electrode. The low temperature EPR spectrum of the oxidatively electrolyzed solution of (NEt4)[Ni(S2COEt)3] indicates the presence of [NiIII(S2COEt)3], which disproportionates to Ni(S2COEt)2, and the dimer of the oxidized ethylxanthate ligand, (S2COEt)2 ((S2COEt)2 = C2H5OC(S)SS(S)COC2H5), with a second order rate law. The final products of constant potential electrolysis at the first oxidation peak potentials of S2COEt−, Ni(S2COEt)2, and [Ni(S2COEt)3]− are (S2COEt)2; Ni2+(sol) and (S2COEt)2; and Ni(S2COEt)2 and (S2COEt)2, respectively. The chemical oxidation of S2COEt− to (S2COEt)2, and [Ni(S2COEt)3]− to (S2COEt)2 and Ni(S2COEt)2 were also achieved with iodine. The oxidized ligand in the dimer form can be reduced to S2COEt− with CN− in solution.