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Reinvestigation of the formation of a mononuclear Fe(iii) hydroperoxido complex using high pressure kineticsDedicated to our friend Hans Toftlund who died suddenly on 27 November 2009.Electronic supplementary information (ESI) available: Kinetic measurement data and plots. CCDC reference numbers 772151-772156. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0dt00247j
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). T...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Online Access: | Get full text |
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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
.
With an activation volume close to zero a pure interchange mechanism is suggested for the formation of [Fe(bztpen)OOH]
2+
. |
|---|---|
| ISSN: | 1477-9226 1477-9234 |
| DOI: | 10.1039/c0dt00247j |