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 volumetrically in moderately alkaline media (pH = 8 -9.5). Reduction of the nitrosyl 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 NH2OH = 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 radicals, initiated by a binuclear intermediate yielding N-2 or N2O and a slower one through formation of Fe(CN)(5)NO4- as a stable intermediate yielding N-2. A kinetic model was constructed which describes both the reduction of nitrosyl complex and the catalytic disproportionation reactions of hydroxylamine.