Activation parameters as mechanistic probes in the TAML iron(V)-oxo oxidations of hydrocarbons.
Identifieur interne : 000645 ( Main/Exploration ); précédent : 000644; suivant : 000646Activation parameters as mechanistic probes in the TAML iron(V)-oxo oxidations of hydrocarbons.
Auteurs : Soumen Kundu [États-Unis] ; Jasper Van Kirk Thompson ; Longzhu Q. Shen ; Matthew R. Mills ; Emile L. Bominaar ; Alexander D. Ryabov ; Terrence J. CollinsSource :
- Chemistry (Weinheim an der Bergstrasse, Germany) [ 1521-3765 ] ; 2015.
Descripteurs français
- KwdFr :
- MESH :
English descriptors
- KwdEn :
- MESH :
- chemical , chemistry : Anthracenes, Hydrocarbons, Iron.
- Kinetics, Oxidation-Reduction, Thermodynamics.
Abstract
The results of low-temperature investigations of the oxidations of 9,10-dihydroanthracene, cumene, ethylbenzene, [D10]ethylbenzene, cyclooctane, and cyclohexane by an iron(V)-oxo TAML complex (2; see Figure 1) are presented, including product identification and determination of the second-order rate constants k2 in the range 233-243 K and the activation parameters (ΔH(≠) and ΔS(≠)). Statistically normalized k2 values (log k2') correlate linearly with the C-H bond dissociation energies DC-H, but ΔH(≠) does not. The point for 9,10-dihydroanthracene for the ΔH(≠) vs. DC-H correlation lies markedly off a common straight line of best fit for all other hydrocarbons, suggesting it proceeds via an alternate mechanism than the rate-limiting C-H bond homolysis promoted by 2. Contribution from an electron-transfer pathway may be substantial for 9,10-dihydroanthracene. Low-temperature kinetic measurements with ethylbenzene and [D10]ethylbenzene reveal a kinetic isotope effect of 26, indicating tunneling. The tunnel effect is drastically reduced at 0 °C and above, although it is an important feature of the reactivity of TAML activators at lower temperatures. The diiron(IV) μ-oxo dimer that is often a common component of the reaction medium involving 2 also oxidizes 9,10-dihydroanthracene, although its reactivity is three orders of magnitude lower than that of 2.
DOI: 10.1002/chem.201405024
PubMed: 25410933
Affiliations:
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Shen</name></author><author><name sortKey="Mills, Matthew R" sort="Mills, Matthew R" uniqKey="Mills M" first="Matthew R" last="Mills">Matthew R. Mills</name></author><author><name sortKey="Bominaar, Emile L" sort="Bominaar, Emile L" uniqKey="Bominaar E" first="Emile L" last="Bominaar">Emile L. Bominaar</name></author><author><name sortKey="Ryabov, Alexander D" sort="Ryabov, Alexander D" uniqKey="Ryabov A" first="Alexander D" last="Ryabov">Alexander D. Ryabov</name></author><author><name sortKey="Collins, Terrence J" sort="Collins, Terrence J" uniqKey="Collins T" first="Terrence J" last="Collins">Terrence J. Collins</name></author></titleStmt><publicationStmt><idno type="wicri:source">PubMed</idno><date when="2015">2015</date><idno type="RBID">pubmed:25410933</idno><idno type="pmid">25410933</idno><idno type="doi">10.1002/chem.201405024</idno><idno type="wicri:Area/PubMed/Corpus">000A24</idno><idno type="wicri:explorRef" wicri:stream="PubMed" wicri:step="Corpus" wicri:corpus="PubMed">000A24</idno><idno type="wicri:Area/PubMed/Curation">000A24</idno><idno type="wicri:explorRef" wicri:stream="PubMed" wicri:step="Curation">000A24</idno><idno type="wicri:Area/PubMed/Checkpoint">000A24</idno><idno type="wicri:explorRef" wicri:stream="Checkpoint" wicri:step="PubMed">000A24</idno><idno type="wicri:Area/Ncbi/Merge">003F02</idno><idno type="wicri:Area/Ncbi/Curation">003F02</idno><idno type="wicri:Area/Ncbi/Checkpoint">003F02</idno><idno type="wicri:Area/Main/Merge">000645</idno><idno type="wicri:Area/Main/Curation">000645</idno><idno type="wicri:Area/Main/Exploration">000645</idno></publicationStmt><sourceDesc><biblStruct><analytic><title xml:lang="en">Activation parameters as mechanistic probes in the TAML iron(V)-oxo oxidations of hydrocarbons.</title><author><name sortKey="Kundu, Soumen" sort="Kundu, Soumen" uniqKey="Kundu S" first="Soumen" last="Kundu">Soumen Kundu</name><affiliation wicri:level="4"><nlm:affiliation>Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA, 15213 (USA).</nlm:affiliation><orgName type="university">Université Carnegie-Mellon</orgName><country>États-Unis</country><placeName><settlement type="city">Pittsburgh</settlement><region type="state">Pennsylvanie</region></placeName></affiliation></author><author><name sortKey="Thompson, Jasper Van Kirk" sort="Thompson, Jasper Van Kirk" uniqKey="Thompson J" first="Jasper Van Kirk" last="Thompson">Jasper Van Kirk Thompson</name></author><author><name sortKey="Shen, Longzhu Q" sort="Shen, Longzhu Q" uniqKey="Shen L" first="Longzhu Q" last="Shen">Longzhu Q. Shen</name></author><author><name sortKey="Mills, Matthew R" sort="Mills, Matthew R" uniqKey="Mills M" first="Matthew R" last="Mills">Matthew R. Mills</name></author><author><name sortKey="Bominaar, Emile L" sort="Bominaar, Emile L" uniqKey="Bominaar E" first="Emile L" last="Bominaar">Emile L. Bominaar</name></author><author><name sortKey="Ryabov, Alexander D" sort="Ryabov, Alexander D" uniqKey="Ryabov A" first="Alexander D" last="Ryabov">Alexander D. Ryabov</name></author><author><name sortKey="Collins, Terrence J" sort="Collins, Terrence J" uniqKey="Collins T" first="Terrence J" last="Collins">Terrence J. Collins</name></author></analytic><series><title level="j">Chemistry (Weinheim an der Bergstrasse, Germany)</title><idno type="eISSN">1521-3765</idno><imprint><date when="2015" type="published">2015</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>Anthracenes (chemistry)</term><term>Hydrocarbons (chemistry)</term><term>Iron (chemistry)</term><term>Kinetics</term><term>Oxidation-Reduction</term><term>Thermodynamics</term></keywords><keywords scheme="KwdFr" xml:lang="fr"><term>Anthracènes ()</term><term>Cinétique</term><term>Fer ()</term><term>Hydrocarbures ()</term><term>Oxydoréduction</term><term>Thermodynamique</term></keywords><keywords scheme="MESH" type="chemical" qualifier="chemistry" xml:lang="en"><term>Anthracenes</term><term>Hydrocarbons</term><term>Iron</term></keywords><keywords scheme="MESH" xml:lang="en"><term>Kinetics</term><term>Oxidation-Reduction</term><term>Thermodynamics</term></keywords><keywords scheme="MESH" xml:lang="fr"><term>Anthracènes</term><term>Cinétique</term><term>Fer</term><term>Hydrocarbures</term><term>Oxydoréduction</term><term>Thermodynamique</term></keywords></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">The results of low-temperature investigations of the oxidations of 9,10-dihydroanthracene, cumene, ethylbenzene, [D10]ethylbenzene, cyclooctane, and cyclohexane by an iron(V)-oxo TAML complex (2; see Figure 1) are presented, including product identification and determination of the second-order rate constants k2 in the range 233-243 K and the activation parameters (ΔH(≠) and ΔS(≠)). Statistically normalized k2 values (log k2') correlate linearly with the C-H bond dissociation energies DC-H, but ΔH(≠) does not. The point for 9,10-dihydroanthracene for the ΔH(≠) vs. DC-H correlation lies markedly off a common straight line of best fit for all other hydrocarbons, suggesting it proceeds via an alternate mechanism than the rate-limiting C-H bond homolysis promoted by 2. Contribution from an electron-transfer pathway may be substantial for 9,10-dihydroanthracene. Low-temperature kinetic measurements with ethylbenzene and [D10]ethylbenzene reveal a kinetic isotope effect of 26, indicating tunneling. The tunnel effect is drastically reduced at 0 °C and above, although it is an important feature of the reactivity of TAML activators at lower temperatures. The diiron(IV) μ-oxo dimer that is often a common component of the reaction medium involving 2 also oxidizes 9,10-dihydroanthracene, although its reactivity is three orders of magnitude lower than that of 2.</div></front></TEI><affiliations><list><country><li>États-Unis</li></country><region><li>Pennsylvanie</li></region><settlement><li>Pittsburgh</li></settlement><orgName><li>Université Carnegie-Mellon</li></orgName></list><tree><noCountry><name sortKey="Bominaar, Emile L" sort="Bominaar, Emile L" uniqKey="Bominaar E" first="Emile L" last="Bominaar">Emile L. Bominaar</name><name sortKey="Collins, Terrence J" sort="Collins, Terrence J" uniqKey="Collins T" first="Terrence J" last="Collins">Terrence J. Collins</name><name sortKey="Mills, Matthew R" sort="Mills, Matthew R" uniqKey="Mills M" first="Matthew R" last="Mills">Matthew R. Mills</name><name sortKey="Ryabov, Alexander D" sort="Ryabov, Alexander D" uniqKey="Ryabov A" first="Alexander D" last="Ryabov">Alexander D. Ryabov</name><name sortKey="Shen, Longzhu Q" sort="Shen, Longzhu Q" uniqKey="Shen L" first="Longzhu Q" last="Shen">Longzhu Q. Shen</name><name sortKey="Thompson, Jasper Van Kirk" sort="Thompson, Jasper Van Kirk" uniqKey="Thompson J" first="Jasper Van Kirk" last="Thompson">Jasper Van Kirk Thompson</name></noCountry><country name="États-Unis"><region name="Pennsylvanie"><name sortKey="Kundu, Soumen" sort="Kundu, Soumen" uniqKey="Kundu S" first="Soumen" last="Kundu">Soumen Kundu</name></region></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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