15740-92-8Relevant academic research and scientific papers
The oxidation of hydrogen peroxide by tris(polypyridine) complexes of osmium(III), iron(III), ruthenium(III), and nickel(III) in aqueous media
Macartney, Donal H.
, p. 1936 - 1942 (2007/10/02)
The stoichiometry and kinetics of the oxidation of hydrogen peroxide by tris(2,2'-bipyridine) and tris(4,4'-dimethyl-2,2'bipyridine) complexes of osmium(III), iron(III), ruthenium(III), and nickel(III) were studied in acidic and neutral aqueous media at 25 deg C and I = 0.50 M (LiCF3SO3).The reaction is observed with quantitative yields of dioxygen gas.The observed rate constants displayed an inverse acid dependence over the pH range 6.0-8.5; kobsd = k1 + k2K1/+>, attributed to the oxidations of H2O2(k1) and HO2-(k2).An application of the Marcus theory relationship to the cross-reaction data gave a self-exchange rate constant of E-2 - E-1 M-1s-1 for the HO2-/HO2 couple.The electron exchange rate constant is evaluated in terms of the inner-sphere and solvent reorganizational barriers and is compared to values repoted for other small molecule couples.Rate and activation parameters for the reduction of the nickel(III) complexes by the hydroxide ion have been determined and are compared with corresponding values for other metal tris(polypyridine) complexes.
The oxidation of a nickel(II) oxime complex by polypyridine iron(III) ions in acidic aqueous media. Formation of a Ni(IV) species
Macartney, D. H.,McAuley, A.
, p. 103 - 108 (2007/10/02)
The kinetics of the oxidation of a nickel(II) oxime complex by a series of iron(III) phenanthroline and bipyridine cations, Fe(LL)33+, have been investigated.The overall reaction Ni(II)(H2L)2+ + 2Fe(LL)33+ -> Ni(IV)L2+ + 2Fe(LL)32+ + 2H+ is considered to take place via two one-electron steps, the first (rate-determining) process yielding Ni(III)(H2L)3+ being followed by very rapid oxidation to the nickel(IV) product.The second order rate constants at 25 deg C in 0.50 M p-toluenesulphonic acid are : Fe(dmbpy)33+, 1.32x103 M-1s-1; Fe(dmphen)33+, 3.73x103 M-1s-1; Fe(bpy)33+, 3.20x104 M-1s-1; Fe(mphen)33+, 6.83x104 M-1s-1;Fe(phen)33+, 9,16x104 M-1s-1; and Fe(cphen)33+, 5.6x105 M-1s-1.The reactions are outer-sphere in character.The rate of the corresponding cross reaction of nickel(II) species with Ru(bipy)33+ (k12 = 1.1x106 M-1s-1) has also been measured.Activation parameters have been incorporated in a Marcus theory correlation to yield information (k12 ca. 3x103 M-1s-1) for the NiII(H2L)2+/Ni(H2L)3+ electron exchange reaction.This value is compared with exchange parameters for Ni(II)/Ni(III) tetraaza-macrocycle and other similar systems.
