Kinetics and mechanism of oxidation of hydroxylamine by 12-tungstocobaltate (III) ion in acetate buffer

The stoichiometry of the title reaction is expressed by the equation 4[(CoU )-U-III](5-) + 2NH(2)OH --> 4[(CoU)-U-II](6-) + N2O + 4H(+) + H2O The absorbancy of the complex formed between hydroxylamine and [(CoU)-U-III ](5-) and the rate increases with decrease in [H+]. There is an excellent a greement between the rate law derived from the mechanism based on the exclu sive reactivity of NH2OH though another mechanism based on the simultaneous reactivity of NH2OH and NH3OH+, which is the dominant species of hydroxyla mine in solutions, also leads to a late law having satisfactory correlation with the results. The high reactivity of NH2OH is ascribed to the coordina tion of the nitrogen atom in NH2OH. Tie similar coordination by NH3OH+ is i mprobable because the lone pair is coordinated to the proton. Hence, the fo rmation of a coordinated complex is an essential requirement for the progre ss of the reaction. The consideration that Co-III atom in 12-tungstocobalta te (III) ion is completely shielded by the tungstate framework, an outer-sp here electron transfer is more probable.