Reinvestigation of the formation of a mononuclear Fe(III) hydroperoxido complex using high pressure kinetics

Previous stopped flow kinetic experiments suggested an interchange associative mechanism for the ligand substitution reaction, [Fe(bztpen)(OMe)](2+) + H(2)O(2)--> {[Fe(bztpen)(OMe)(HOOH)](2+)}(++)--> [Fe(bztpen)(OOH)](2+) + MeOH (bztpen = N-benzyl-N, N',N'tris(2-methylpyridyl)-ethyle...

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Published in:Dalton transactions : an international journal of inorganic chemistry 2010-01, Vol.39 (33), p.7768
Main Authors: Nebe, Thomas, Beitat, Alexander, Würtele, Christian, Dücker-Benfer, Carlos, van Eldik, Rudi, McKenzie, Christine J, Schindler, Siegfried
Format: Article
Language:English
Subjects:
Cobalt
Crystallography, X-Ray
Ferric Compounds
Ferrous Compounds
Hydrogen Peroxide
Iron
Kinetics
Ligands
Models, Molecular
Molecular Structure
Nitric Oxide
Oxygen
Pressure
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Summary:Previous stopped flow kinetic experiments suggested an interchange associative mechanism for the ligand substitution reaction, [Fe(bztpen)(OMe)](2+) + H(2)O(2)--> {[Fe(bztpen)(OMe)(HOOH)](2+)}(++)--> [Fe(bztpen)(OOH)](2+) + MeOH (bztpen = N-benzyl-N, N',N'tris(2-methylpyridyl)-ethylenediamine). Thus a seven-coordinate transition state containing both the leaving methoxide and the incoming hydrogen peroxide ligands was proposed. On the basis of high pressure kinetic data we can now conclude that this is not the case since the rate of the reaction is independent of pressure for the formation of the purple low spin transient hydroperoxido complex, [Fe(bztpen)(OOH)](2+). [Fe(bztpen)(OOH)](2+) has so far proved to be too short-lived for solid state isolation. As part of our ongoing pursuit of this elusive species we have structurally characterised the nitrosyl and acetate iron(II) complexes, [Fe(bztpen)(NO)](OTf)(2) and [Fe(bztpen)(OAc)](BPh(4)), as well as the air stable Co(II) complexes [Co(bztpen)Cl)]BF(4), [Co(metpen)Cl]SbF(6) and [Co(bztpen)(OAc)]BPh(4). We did not realise our aim of accessing stable Co(III) hydroperoxido or peroxido complexes by reaction of the cobalt complexes with H(2)O(2).
ISSN:1477-9226
1477-9234
DOI:10.1039/c0dt00247j