Kinetic studies on the reduction of a nickel (III) oxime-imine complex by sulphur (IV) and selenium (IV)

摘要

The kinetics of the reduction of [Ni~(III)(L~1)]~(2+) (where HL~1 = 15-amino-3-methyl-4,7,10,13-tetraazapentadec-3-en-2-one oxime) by sulphur(IV) and selenium (IV) over the regions pH 2.50-8.02 and 2.01-4.00 respectively have been investigated at 30鉉. Attempts were made to evaluate the reactivity of all the reacting species of sulphur(IV) and selenium(IV) by considering suitable pH ranges. The oxidation of SO_2.H_2O and HSO_3~- is proposed to proceed through the formation of a hydrogen-bonded adduct. The reaction with SO_3~(2-) seems to follow a direct outer-sphere route which is well supported by Marcus cross-relation calculation. The oxidation of HSeO_3~- is = 10~3 times slower than that of H_2SeO_3. The kinetic data indicate that the oxidationof sulphur(IV) by [Ni~(III))]~(2+) is much more favourable as compared to the corresponding oxidation of selenium(IV).