Issue 9, 2002

Kinetic and mechanistic studies on the oxidation of hydroxylamine by a tri-bridged manganese(iv,iv) dimer in weakly acidic media

Abstract

The complex ion, [MnIV2(μ-O)2(μ-MeCO2)(bipy)2(H2O)2]3+ (13+) (bipy = 2,2′-bipyridine) and its aqua derivatives [Mn2IV(μ-O)2(bipy)2(H2O)4]4+ (24+) and [Mn2IV(μ-O)2(μ-MeCO2)(bipy)(H2O)4]3+ (33+) coexists in rapid equilibria in aqueous buffer in the presence of excess of bipy and MeCO2 in the range pH 4.00–5.30. The solutions are reasonably stable up to pH 5.50 and react quantitatively with hydroxylamine to produce manganese(II) and N2O. The reactions follow simple first-order kinetics in the presence of excess hydroxylamine. There is UV–vis spectral evidence for the intermediate MnIII,IV complex, [(bipy)2MnIII(μ-O)2MnIV(bipy)2]3+, in the presence of excess bipy and deficit hydroxylamine which supports that 13+ and its hydrolytic derivatives are reduced by one-electron steps. Increased extent of aquation at the manganese(IV) centre leads to increased kinetic activity in the order: 13+ < 24+ < 33+. The rate of reduction increased with an increase in the concentration of hydroxylamine but decreased with increase in cbipy and cOAc. The mild oxidising character of the complex ion along with major structural changes associated with one-electron oxidation of hydroxylamine disfavours an outer-sphere pathway. The overall first-order rate constants decrease linearly with increased mol% of D2O suggesting proton-coupled electron transfer pathways.

Graphical abstract: Kinetic and mechanistic studies on the oxidation of hydroxylamine by a tri-bridged manganese(iv,iv) dimer in weakly acidic media

Article information

Article type
Paper
Submitted
12 Nov 2001
Accepted
30 Jan 2002
First published
27 Mar 2002

J. Chem. Soc., Dalton Trans., 2002, 2047-2052

Kinetic and mechanistic studies on the oxidation of hydroxylamine by a tri-bridged manganese(IV,IV) dimer in weakly acidic media

S. Banerjee, U. R. Choudhury, R. Banerjee and S. Mukhopadhyay, J. Chem. Soc., Dalton Trans., 2002, 2047 DOI: 10.1039/B110352K

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Spotlight

Advertisements