Please use this identifier to cite or link to this item: https://hdl.handle.net/10356/163536
Title: Sterically stabilized end-on superoxocopper(II) complexes and mechanistic insights into their reactivity with O−H, N−H, and C−H substrates
Authors: Quek, Sebastian Y.
Debnath, Suman
Laxmi, Shoba
van Gastel, Maurice
Krämer, Tobias
England, Jason
Keywords: Science::Chemistry
Issue Date: 2021
Source: Quek, S. Y., Debnath, S., Laxmi, S., van Gastel, M., Krämer, T. & England, J. (2021). Sterically stabilized end-on superoxocopper(II) complexes and mechanistic insights into their reactivity with O−H, N−H, and C−H substrates. Journal of the American Chemical Society, 143(47), 19731-19747. https://dx.doi.org/10.1021/jacs.1c07837
Project: M4081442
000416-00001
RG8/19 (S)
002689-00001
Journal: Journal of the American Chemical Society
Abstract: Instability of end-on superoxocopper(II) complexes, with respect to conversion to peroxo-bridged dicopper(II) complexes, has largely constrained their study to very low temperatures. This limits their kinetic capacity to oxidize substrates. In response, we have developed a series of bulky ligands, Ar3-TMPA (Ar = tpb, dpb, dtbpb), and used them to support copper(I) complexes that react with O2 to yield [CuII(η1-O2•-)(Ar3-TMPA)]+ species, which are stable against dimerization at all temperatures. Binding of O2 saturates at subambient temperatures and can be reversed by warming. The onset of oxygenation for the Ar = tpb and dpb systems is observed at 25 °C, and all three [CuII(η1-O2•-)(Ar3-TMPA)]+ complexes are stable against self-decay at temperatures of ≤-20 °C. This provides a wide temperature window for study of these complexes, which was exploited by performing extensive reaction kinetics measurements for [CuII(η1-O2•-)(tpb3-TMPA)]+ using a broad range of O-H, N-H, and C-H bond substrates. This includes correlation of second order rate constants (k2) versus oxidation potentials (Eox) for a range of phenols, construction of Eyring plots, and temperature-dependent kinetic isotope effect (KIE) measurements. The data obtained indicate that reaction with all substrates proceeds via H atom transfer (HAT), reaction with the phenols proceeds with significant charge transfer, and full tunneling of both H and D atoms occurs in the case of 1,2-diphenylhydrazine and 4-methoxy-2,6-di-tert-butylphenol. Oxidation of C-H bonds proved to be kinetically challenging, and whereas [CuII(η1-O2•-)(tpb3-TMPA)]+ can oxidize moderately strong O-H and N-H bonds, it is only able to oxidize very weak C-H bonds.
URI: https://hdl.handle.net/10356/163536
ISSN: 0002-7863
DOI: 10.1021/jacs.1c07837
Schools: School of Physical and Mathematical Sciences 
Rights: © 2021 American Chemical Society. All rights reserved.
Fulltext Permission: none
Fulltext Availability: No Fulltext
Appears in Collections:SPMS Journal Articles

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