Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2009;15(19):4886-95.
doi: 10.1002/chem.200802338.

Generating Cu(II)-oxyl/Cu(III)-oxo species from Cu(I)-alpha-ketocarboxylate complexes and O2: in silico studies on ligand effects and C-H-activation reactivity

Stefan M Huber  1 , Mehmed Z Ertem, Francesco Aquilante, Laura Gagliardi, William B Tolman, Christopher J Cramer
Affiliations

Generating Cu(II)-oxyl/Cu(III)-oxo species from Cu(I)-alpha-ketocarboxylate complexes and O2: in silico studies on ligand effects and C-H-activation reactivity

Stefan M Huber et al. Chemistry. 2009.

Abstract

A mechanism for the oxygenation of Cu(I) complexes with alpha-ketocarboxylate ligands that is based on a combination of density functional theory and multireference second-order perturbation theory (CASSCF/CASPT2) calculations is elaborated. The reaction proceeds in a manner largely analogous to those of similar Fe(II)-alpha-ketocarboxylate systems, that is, by initial attack of a coordinated oxygen molecule on a ketocarboxylate ligand with concomitant decarboxylation. Subsequently, two reactive intermediates may be generated, a Cu-peracid structure and a [CuO](+) species, both of which are capable of oxidizing a phenyl ring component of the supporting ligand. Hydroxylation by the [CuO](+) species is predicted to proceed with a smaller activation free energy. The effects of electronic and steric variations on the oxygenation mechanisms were studied by introducing substituents at several positions of the ligand backbone and by investigating various N-donor ligands. In general, more electron donation by the N-donor ligand leads to increased stabilization of the more Cu(II)/Cu(III)-like intermediates (oxygen adducts and [CuO](+) species) relative to the more Cu(I)-like peracid intermediate. For all ligands investigated, the [CuO](+) intermediates are best described as Cu(II)-O(*-) species with triplet ground states. The reactivity of these compounds in C-H abstraction reactions decreases with more electron-donating N-donor ligands, which also increase the Cu-O bond strength, although the Cu-O bond is generally predicted to be rather weak (with a bond order of about 0.5). A comparison of several methods to obtain singlet energies for the reaction intermediates indicates that multireference second-order perturbation theory is likely more accurate for the initial oxygen adducts, but not necessarily for subsequent reaction intermediates.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Model ligand L0, used for evaluation of the mechanism of the oxygenation reaction shown in Scheme 2, and various substituted derivatives L1 to L6, used to study the influence of substitution effects on the individual steps of the mechanism in Scheme 3.
Figure 2
Figure 2
Isomers of the starting complexes and the oxygen adducts (compare Scheme 3).
Figure 3
Figure 3
N-donor ligands L1 to L12 used to investigate ligand effects on the oxygenation reaction of Scheme 3.
Scheme 1
Scheme 1
General mechanism for the reactivity of Fe(II)-α-ketocarboxylate sites in enzymes and model complexes.
Scheme 2
Scheme 2
Oxygenation of Cu(I)-α-ketocarboxylate complexes 4 and 5.
Scheme 3
Scheme 3
Proposed general mechanism for the oxygenation of CuI-α-ketocarboxylate complexes. The N-donor ligand is depicted only schematically. See also Figures 1 and 2, and Tables 1 and 2 for free energies. Structures in gray are only relevant for ligands L0 to L6.
Scheme 4
Scheme 4
Alternative mechanism for the hydroxylation of the phenyl ring of the N-donor ligand. The N-donor ligand is only depicted schematically. All values in kcal/mol.
Scheme 5
Scheme 5
Model reactions to study the C-H activation reactivity and the strength of the Cu-O bond (see also Table 4). The energetically lowest copper oxo isomer was used for each respective ligand.
See this image and copyright information in PMC

References

    1. Solomon EI, Sundaram UM, Machonkin TE. Chem Rev. 1996;96:2563–2605. - PubMed
    2. Solomon EI, Chen P, Metz M, Lee SK, Palmer AE. Angew Chem Int Ed. 2001;40:4570–4590. - PubMed
    3. Klinman JP. Chem Rev. 1996;96:2541–2561. - PubMed
    4. Decker A, Solomon EI. Curr Opin Chem Biol. 2005;9:152–163. - PubMed
    5. Solomon EI, Sarangi R, Woertink J, Augustine A, Yoon J, Ghosh S. Acc Chem Res. 2007;40:581–591. - PMC - PubMed

    1. Selected recent reviews: Mirica LM, Ottenwaelder X, Stack TDP. Chem Rev. 2004;104:1013–1045.Lewis EA, Tolman WB. Chem Rev. 2004;104:1047–1076.Hatcher L, Karlin KD. J Biol Inorg Chem. 2004;9:669–683.Itoh S. Curr Opin Chem Biol. 2006;10:115–122.Cramer CJ, Tolman WB. Acc Chem Res. 2007;40:601–608.Suzuki M. Acc Chem Res. 2007;40:609–617.Gherman BF, Cramer CJ. Coord Chem Rev. doi: 10.1016/j.ccr.2007.11.018. in press.

    1. Crespo A, Marti MA, Roitberg AE, Amzel LM, Estrin DA. J Am Chem Soc. 2006;128:12817–12828. - PubMed
    2. Kmachi T, Kihara N, Shiota Y, Yoshizawa K. Inorg Chem. 2005;44:4226–4236. - PubMed
    3. Yoshizawa K, Kihara N, Kamachi T, Shiota Y. Inorg Chem. 2006;45:3034–3041. - PubMed
    4. Evans JP, Ahn K, Klinman JP. J Biol Chem. 2003;278:49691–49698. - PubMed
    5. Chen P, Solomon EI. J Am Chem Soc. 2004;126:4991–5000. - PubMed
    6. Klinman JP. J Biol Chem. 2006;281:3013–3016. - PubMed

    1. For examples, see: Kitajima N, Koda T, Iwata Y, Moro-oka Y. J Am Chem Soc. 1990;112:8833–8839.Capdevielle P, Sparfel D, Baranne-Lafont J, Cuong NK, Maumy M. J Chem Soc, Chem Commun. 1990:565–566.Reinaud O, Chapdevielle P, Maumy M. J Chem Soc, Chem Commun. 1990:566–568.Maiti D, Lucas HR, Sarjeant AAN, Karlin KD. J Am Chem Soc. 2007;129:6998–6999.Maiti D, Sarjeant AAN, Karlin KD. Inorg Chem. 2008;47:8736–8747.

    1. Schroeder D, Holtzhausen MC, Schwarz H. J Phys Chem B. 2004;108:14407–14416.

Publication types

LinkOut - more resources