Sehen schwere Kerne Licht am Ende des Tunnels?

Berger, Robert W.

doi:10.1002/ange.200301675

Angewandte Chemie

2004

DOI: 10.1002/ange.200301675

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Sehen schwere Kerne Licht am Ende des Tunnels?

Robert W. Berger

Abstract: Auf direktem Wege: Tieftemperaturexperimente und Rechnungen zur Ringerweiterung von (1‐Methylcyclobutyl)fluorcarben, bei der sich die schweren Kerne beträchtlich verschieben, deuten darauf hin, dass Tunnelprozesse nicht nur für leichte Kerne günstiger sein können als das klassische Überschreiten der Aktivierungsbarriere entlang der „Passstraße“ (siehe Bild).

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Aromatic Hydroxylation in a Copper Bis(imine) Complex Mediated by a μ‐η²:η² Peroxo Dicopper Core: A Mechanistic Scenario

Sander

Henß

Näther

et al. 2008

Chemistry A European J

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Detailed mechanistic studies on the ligand hydroxylation reaction mediated by a copper bis(imine) complex are presented. Starting from a structural analysis of the CuI complex and the CuII product with a hydroxylated ligand, the optical absorption and vibrational spectra of starting material and product are analyzed. Kinetic analysis of the ligand hydroxylation reaction shows that O2 binding is the rate-limiting step. The reaction proceeds much faster in methanol than in acetonitrile. Moreover, an inverse kinetic isotope effect (KIE) is evidenced for the reaction in acetonitrile, which is attributed to a sterically congested transition state leading to the peroxo adduct. In methanol, however, no KIE is observed. A DFT analysis of the oxygenation reaction mediated by the micro-eta2:eta2 peroxo core demonstrates that the major barrier after O2 binding corresponds to electrophilic attack on the arene ring. The relevant orbital interaction occurs between the sigma* orbital of the Cu2O2 unit and the HOMO of the ligand. On the basis of the activation energy for the rate-limiting step (18.3 kcal mol(-1)) this reaction is thermally allowed, in agreement with the experimental observation. The calculations also predict the presence of a stable dienone intermediate which, however, escaped experimental detection so far. Reasons for these findings are considered. The implications of the results for the mechanism of tyrosinase are discussed.

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Aromatic Hydroxylation in a Copper Bis(imine) Complex Mediated by a μ‐η²:η² Peroxo Dicopper Core: A Mechanistic Scenario

Sander

Henß

Näther

et al. 2008

Chemistry A European J

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Sehen schwere Kerne Licht am Ende des Tunnels?

Cited by 1 publication

References 63 publications

Aromatic Hydroxylation in a Copper Bis(imine) Complex Mediated by a μ‐η²:η² Peroxo Dicopper Core: A Mechanistic Scenario

Aromatic Hydroxylation in a Copper Bis(imine) Complex Mediated by a μ‐η²:η² Peroxo Dicopper Core: A Mechanistic Scenario

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Sehen schwere Kerne Licht am Ende des Tunnels?

Cited by 1 publication

References 63 publications

Aromatic Hydroxylation in a Copper Bis(imine) Complex Mediated by a μ‐η2:η2 Peroxo Dicopper Core: A Mechanistic Scenario

Aromatic Hydroxylation in a Copper Bis(imine) Complex Mediated by a μ‐η2:η2 Peroxo Dicopper Core: A Mechanistic Scenario

Contact Info

Product

Resources

About

Aromatic Hydroxylation in a Copper Bis(imine) Complex Mediated by a μ‐η²:η² Peroxo Dicopper Core: A Mechanistic Scenario

Aromatic Hydroxylation in a Copper Bis(imine) Complex Mediated by a μ‐η²:η² Peroxo Dicopper Core: A Mechanistic Scenario