Mechanistic Insights from Reactions between Copper(II)-Phenoxyl Complexes and Substrates with Activated C-H Bonds.
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| Title: | Mechanistic Insights from Reactions between Copper(II)-Phenoxyl Complexes and Substrates with Activated C-H Bonds. |
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| Authors: | Pratt, Russell C.1, Stack, T. Daniel P.1 stack@stanford.edu |
| Source: | Inorganic Chemistry. 4/4/2005, Vol. 44 Issue 7, p2367-2375. 9p. 7 Diagrams, 3 Charts, 7 Graphs. |
| Subjects: | Copper, Hydrogen bonding, Chemical reactions, Galactose, Deuterium, Inorganic chemistry |
| Abstract: | The reactivities of two copper(II)-phenoxyl analogues of the oxidized, active form of the metalloenzyme galactose oxidase, [1tBu2]+ and [2tBu2]+, have been studied using the substrates benzyl alcohol and 9,10-dihydroanthracene, for a total of four reactions. The reaction stoichiometries in all cases show a 2:1 ratio of oxidant to benzaldehyde or anthracene product, indicating that [1tBu2]+ and [2tBu2]+ behave ultimately as only one-electron oxidants, but the reaction kinetics each indicate that only a single copper(II)-phenoxyl complex is involved in the rate-determining step. For each substrate, rate laws indicate that [1tBu2]+ and [2tBu2]+ react by different mechanisms: one proceeds by a simple bimolecular reaction, while the other first enters into a substrate-binding equilibrium before subsequently reacting by an intramolecular reaction. The reactions proceeding by the latter mechanism have faster overall rates, which correlates to a lower entropic barrier for the substrate-binding mechanism. Correlation of the reaction rates with the C-H bond dissociation energies of substrates as well as significant deuterium kinetic isotope effects indicates that the rate-determining steps involve hydrogen atom abstraction from the activated C-H bonds. A variable-temperature study (268-308 K) of the nonclassical KIE of the [1tBU2]+/benzyl alcohol reaction (kH/kD = 15 at 298 K) failed to show evidence for quantum tunneling. The rapid sequence by which a second 1 equiv of copper(II)-phenoxyl oxidant completes the reaction after the rate- and product-determining hydrogen atom abstraction step cannot be probed kinetically. Comparisons are made to the reactivities of other copper(II)-phenoxyl complexes reported in the literature and to galactose oxidase itself. [ABSTRACT FROM AUTHOR] |
| Copyright of Inorganic Chemistry is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
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| Items | – Name: Title Label: Title Group: Ti Data: Mechanistic Insights from Reactions between Copper(II)-Phenoxyl Complexes and Substrates with Activated C-H Bonds. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Pratt%2C+Russell+C%2E%22">Pratt, Russell C.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Stack%2C+T%2E+Daniel+P%2E%22">Stack, T. Daniel P.</searchLink><relatesTo>1</relatesTo><i> stack@stanford.edu</i> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Inorganic+Chemistry%22">Inorganic Chemistry</searchLink>. 4/4/2005, Vol. 44 Issue 7, p2367-2375. 9p. 7 Diagrams, 3 Charts, 7 Graphs. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Copper%22">Copper</searchLink><br /><searchLink fieldCode="DE" term="%22Hydrogen+bonding%22">Hydrogen bonding</searchLink><br /><searchLink fieldCode="DE" term="%22Chemical+reactions%22">Chemical reactions</searchLink><br /><searchLink fieldCode="DE" term="%22Galactose%22">Galactose</searchLink><br /><searchLink fieldCode="DE" term="%22Deuterium%22">Deuterium</searchLink><br /><searchLink fieldCode="DE" term="%22Inorganic+chemistry%22">Inorganic chemistry</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: The reactivities of two copper(II)-phenoxyl analogues of the oxidized, active form of the metalloenzyme galactose oxidase, [1tBu2]+ and [2tBu2]+, have been studied using the substrates benzyl alcohol and 9,10-dihydroanthracene, for a total of four reactions. The reaction stoichiometries in all cases show a 2:1 ratio of oxidant to benzaldehyde or anthracene product, indicating that [1tBu2]+ and [2tBu2]+ behave ultimately as only one-electron oxidants, but the reaction kinetics each indicate that only a single copper(II)-phenoxyl complex is involved in the rate-determining step. For each substrate, rate laws indicate that [1tBu2]+ and [2tBu2]+ react by different mechanisms: one proceeds by a simple bimolecular reaction, while the other first enters into a substrate-binding equilibrium before subsequently reacting by an intramolecular reaction. The reactions proceeding by the latter mechanism have faster overall rates, which correlates to a lower entropic barrier for the substrate-binding mechanism. Correlation of the reaction rates with the C-H bond dissociation energies of substrates as well as significant deuterium kinetic isotope effects indicates that the rate-determining steps involve hydrogen atom abstraction from the activated C-H bonds. A variable-temperature study (268-308 K) of the nonclassical KIE of the [1tBU2]+/benzyl alcohol reaction (kH/kD = 15 at 298 K) failed to show evidence for quantum tunneling. The rapid sequence by which a second 1 equiv of copper(II)-phenoxyl oxidant completes the reaction after the rate- and product-determining hydrogen atom abstraction step cannot be probed kinetically. Comparisons are made to the reactivities of other copper(II)-phenoxyl complexes reported in the literature and to galactose oxidase itself. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Inorganic Chemistry is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1021/ic048695i Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 9 StartPage: 2367 Subjects: – SubjectFull: Copper Type: general – SubjectFull: Hydrogen bonding Type: general – SubjectFull: Chemical reactions Type: general – SubjectFull: Galactose Type: general – SubjectFull: Deuterium Type: general – SubjectFull: Inorganic chemistry Type: general Titles: – TitleFull: Mechanistic Insights from Reactions between Copper(II)-Phenoxyl Complexes and Substrates with Activated C-H Bonds. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Pratt, Russell C. – PersonEntity: Name: NameFull: Stack, T. Daniel P. IsPartOfRelationships: – BibEntity: Dates: – D: 04 M: 04 Text: 4/4/2005 Type: published Y: 2005 Identifiers: – Type: issn-print Value: 00201669 Numbering: – Type: volume Value: 44 – Type: issue Value: 7 Titles: – TitleFull: Inorganic Chemistry Type: main |
| ResultId | 1 |
