The oxidized complex of nickel with 4-carboxy-1,2-cyclohexanedionedioxime in alkaline media

The reaction of oxygen with a nickel(II) complex of 4-carboxy-1,2-cyclohexanedionedioxime in alkaline media was studied spectrophotometrically, polarographically, and by spectrophotometric titrations with tin(II) chloride. Magnetic susceptibility measurements were also performed. The rate of formation of the oxidized complex was found to be first order at 25° and 50°. The average values obtained for the rate constant k'₁ are (2.71 ± 0.23) x 10^-2 h^-1 (25°), spectrophotometrically; (5.99 ± 0.83) x 10^-2 h^-1 (50°), polarographically; (4.98 ± 0.90) x 10^-2 h^-1 (50°), titrimetrically; (2.87 ± 0.29) x 10^-2 h^-1 (50°), curve fitting. The value obtained for the rate constant K'₂ is (1.59 ± 0.16) x 10^-2 h^-1 (50°), curve fitting, The effect of reducing agents on the formation of the oxidized complex was studied. It was found that tin(II) chloride, hydrazine sulfate, and hydroxylammonium chloride prevented the formation of the oxidized complex. A reaction mechanism for the formation and decomposition of the oxidized complex is proposed.