Kinetic and isotopic studies on the reaction of nitrous acid with cis-chlorobis(ethylenediamine)(hydroxylamine)cobalt(III)
Abstract
Nitrous acid reacts with the title complex giving N2O and N2, the former gas being the major product. At [H+] > 0.1 mol dm–3 the rate law is Rate α[H+][HNO2][complex], while at lower acidities the reaction is retarded by H+ with a rate law: Rate ∝[H+]–1[HNO2][complex]. At [H+]ca. 0.1 mol dm–3 there are deviations from these rate laws. The corresponding complex with O-methylhydroxylamine does not react with HNO2. The reaction at higher acidities is assumed to involve rate-determining formation of an O-nitroso-species, NH2ONO, which undergoes re-arrangement to give a co-ordinated hyponitrite species which either decomposes to N2O or reacts via a nitrous acid-catalysed reaction to give N2. The rate law containing the [H+]–1 term is less easy to interpret, and may involve attack of the nitrosating agent on a doubly deprotonated complex.