KINETICS AND MECHANISM OF THE REACTION BETWEEN PENTACYANONITROSYLFERRATE(II) AND HYDROXYLAMINE

The kinetics of the reaction between pentacyanonitrosylferrate(II) and hydroxylamine was studied spectrophotometrically and gas volumetrical ly in moderately alkaline media (pH = 8 -9.5). Reduction of the nitros yl ligand takes place according to the following stoichiometry: Fe(CN) (5)NO2- + NH2OH = Fe(CN)(5)H2O3- + N2O + H+ The aquocomplex catalyses the following two disproportionation reactions of hydroxylamine: 4 NH2 OH = N2O + 2NH(3) + 2H(2)O and 3NH(2)OH = N-2 + NH3 + 3H(2)O Two paths for disproportionation were identified: a fast route, probably via ra dicals, initiated by a binuclear intermediate yielding N-2 or N2O and a slower one through formation of Fe(CN)(5)NO4- as a stable intermedia te yielding N-2. A kinetic model was constructed which describes both the reduction of nitrosyl complex and the catalytic disproportionation reactions of hydroxylamine.