Engineering the Oxidative Potency of Non-Heme Iron(IV) Oxo Complexes in Water for C-H Oxidation by a cis Donor and Variation of the Second Coordination Sphere
(2021) In Inorganic Chemistry 60(3). p.1975-1984- Abstract
A series of iron(IV) oxo complexes, which differ in the donor (CH2py or CH2COO-) cis to the oxo group, three with hemilabile pendant donor/second coordination sphere base/acid arms (pyH/py or ROH), have been prepared in water at pH 2 and 7. The νFe=O values of 832 ± 2 cm-1 indicate similar FeIV=O bond strengths; however, different reactivities toward C-H substrates in water are observed. HAT occurs at rates that differ by 1 order of magnitude with nonclassical KIEs (kH/kD = 30-66) consistent with hydrogen atom tunneling. Higher KIEs correlate with faster reaction rates as well as a greater thermodynamic stability of the iron(III) resting states. A doubling in rate from pH 7 to pH 2 for substrate C-H oxidation by the most potent complex,... (More)
A series of iron(IV) oxo complexes, which differ in the donor (CH2py or CH2COO-) cis to the oxo group, three with hemilabile pendant donor/second coordination sphere base/acid arms (pyH/py or ROH), have been prepared in water at pH 2 and 7. The νFe=O values of 832 ± 2 cm-1 indicate similar FeIV=O bond strengths; however, different reactivities toward C-H substrates in water are observed. HAT occurs at rates that differ by 1 order of magnitude with nonclassical KIEs (kH/kD = 30-66) consistent with hydrogen atom tunneling. Higher KIEs correlate with faster reaction rates as well as a greater thermodynamic stability of the iron(III) resting states. A doubling in rate from pH 7 to pH 2 for substrate C-H oxidation by the most potent complex, that with a cis-carboxylate donor, [FeIVO(Htpena)]2+, is observed. Supramolecular assistance by the first and second coordination spheres in activating the substrate is proposed. The lifetime of this complex in the absence of a C-H substrate is the shortest (at pH 2, 3 h vs up to 1.3 days for the most stable complex), implying that slow water oxidation is a competing background reaction. The iron(IV)=O complex bearing an alcohol moiety in the second coordination sphere displays significantly shorter lifetimes due to a competing selective intramolecular oxidation of the ligand.
(Less)
- author
- Wegeberg, Christina ; Skavenborg, Mathias L. ; Liberato, Andrea ; McPherson, James N. ; Browne, Wesley R. ; Hedegård, Erik D. LU and McKenzie, Christine J.
- organization
- publishing date
- 2021
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Inorganic Chemistry
- volume
- 60
- issue
- 3
- pages
- 1975 - 1984
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- pmid:33470794
- scopus:85100266929
- ISSN
- 0020-1669
- DOI
- 10.1021/acs.inorgchem.0c03441
- language
- English
- LU publication?
- yes
- id
- 6a457ebf-da42-45b0-a36a-ab1b3dc0485d
- date added to LUP
- 2021-02-15 09:58:28
- date last changed
- 2024-09-19 16:23:48
@article{6a457ebf-da42-45b0-a36a-ab1b3dc0485d, abstract = {{<p>A series of iron(IV) oxo complexes, which differ in the donor (CH2py or CH2COO-) cis to the oxo group, three with hemilabile pendant donor/second coordination sphere base/acid arms (pyH/py or ROH), have been prepared in water at pH 2 and 7. The νFe=O values of 832 ± 2 cm-1 indicate similar FeIV=O bond strengths; however, different reactivities toward C-H substrates in water are observed. HAT occurs at rates that differ by 1 order of magnitude with nonclassical KIEs (kH/kD = 30-66) consistent with hydrogen atom tunneling. Higher KIEs correlate with faster reaction rates as well as a greater thermodynamic stability of the iron(III) resting states. A doubling in rate from pH 7 to pH 2 for substrate C-H oxidation by the most potent complex, that with a cis-carboxylate donor, [FeIVO(Htpena)]2+, is observed. Supramolecular assistance by the first and second coordination spheres in activating the substrate is proposed. The lifetime of this complex in the absence of a C-H substrate is the shortest (at pH 2, 3 h vs up to 1.3 days for the most stable complex), implying that slow water oxidation is a competing background reaction. The iron(IV)=O complex bearing an alcohol moiety in the second coordination sphere displays significantly shorter lifetimes due to a competing selective intramolecular oxidation of the ligand. </p>}}, author = {{Wegeberg, Christina and Skavenborg, Mathias L. and Liberato, Andrea and McPherson, James N. and Browne, Wesley R. and Hedegård, Erik D. and McKenzie, Christine J.}}, issn = {{0020-1669}}, language = {{eng}}, number = {{3}}, pages = {{1975--1984}}, publisher = {{The American Chemical Society (ACS)}}, series = {{Inorganic Chemistry}}, title = {{Engineering the Oxidative Potency of Non-Heme Iron(IV) Oxo Complexes in Water for C-H Oxidation by a cis Donor and Variation of the Second Coordination Sphere}}, url = {{http://dx.doi.org/10.1021/acs.inorgchem.0c03441}}, doi = {{10.1021/acs.inorgchem.0c03441}}, volume = {{60}}, year = {{2021}}, }