Privileged Role of Thiolate as the Axial Ligand in Hydrogen Atom Transfer Reactions by Oxoiron(IV) Complexes in Shaping the Potential Energy Surface and Inducing Significant H-Atom Tunneling

Johannes Klein; Debasish Mandal; Wei-Min Ching; Dibyendu Mallick; Lawrence Que; Sason Shaik

doi:10.1021/jacs.7b11300

Privileged Role of Thiolate as the Axial Ligand in Hydrogen Atom Transfer Reactions by Oxoiron(IV) Complexes in Shaping the Potential Energy Surface and Inducing Significant H-Atom Tunneling

Johannes Klein, Debasish Mandal, Wei-Min Ching, Dibyendu Mallick, Lawrence Que, Sason Shaik

Chemistry (Twin Cities)

Research output: Contribution to journal › Article › peer-review

33 Scopus citations

Abstract

An H/D kinetic isotope effect (KIE) of 80 is found at -20 °C for the oxidation of 9,10-dihydroanthracene by [Fe^IV(O)(TMCS)]⁺, a complex supported by the tetramethylcyclam (TMC) macrocycle with a tethered thiolate. This KIE value approaches that previously predicted by DFT calculations. Other [Fe^IV(O)(TMC)(anion)] complexes exhibit values of 20, suggesting that the thiolate ligand of [Fe^IV(O)(TMCS)]⁺ plays a unique role in facilitating tunneling. Calculations show that tunneling is most enhanced (a) when the bond asymmetry between C-H bond breaking and O-H bond formation in the transition state is minimized, and (b) when the electrostatic interactions in the O - -H - -C moiety are maximal. These two factors - which peak for the best electron donor, the thiolate ligand - afford a slim and narrow barrier through which the H-atom can tunnel most effectively.

Original language	English (US)
Pages (from-to)	18705-18713
Number of pages	9
Journal	Journal of the American Chemical Society
Volume	139
Issue number	51
DOIs	https://doi.org/10.1021/jacs.7b11300
State	Published - Dec 27 2017

Bibliographical note

Funding Information:
This work was supported at the University of Minnesota by grants from the U.S. National Science Foundation (CHE-1361773 and 1665391 to L.Q.), a Feodor Lynen Research Fellowship from the Alexander von Humboldt Foundation to J.E.M.N.K., and a postdoctoral fellowship to W.-M.C. from the Ministry of Science and Technology, Taiwan. S.S. acknowledges support from the Israel Science Foundation (ISF grant 1183/13).

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© 2017 American Chemical Society.

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Klein, J., Mandal, D., Ching, W.-M., Mallick, D., Que, L., & Shaik, S. (2017). Privileged Role of Thiolate as the Axial Ligand in Hydrogen Atom Transfer Reactions by Oxoiron(IV) Complexes in Shaping the Potential Energy Surface and Inducing Significant H-Atom Tunneling. Journal of the American Chemical Society, 139(51), 18705-18713. https://doi.org/10.1021/jacs.7b11300

Privileged Role of Thiolate as the Axial Ligand in Hydrogen Atom Transfer Reactions by Oxoiron(IV) Complexes in Shaping the Potential Energy Surface and Inducing Significant H-Atom Tunneling. / Klein, Johannes; Mandal, Debasish; Ching, Wei-Min et al.
In: Journal of the American Chemical Society, Vol. 139, No. 51, 27.12.2017, p. 18705-18713.

Research output: Contribution to journal › Article › peer-review

Klein, J, Mandal, D, Ching, W-M, Mallick, D, Que, L & Shaik, S 2017, 'Privileged Role of Thiolate as the Axial Ligand in Hydrogen Atom Transfer Reactions by Oxoiron(IV) Complexes in Shaping the Potential Energy Surface and Inducing Significant H-Atom Tunneling', Journal of the American Chemical Society, vol. 139, no. 51, pp. 18705-18713. https://doi.org/10.1021/jacs.7b11300

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abstract = "An H/D kinetic isotope effect (KIE) of 80 is found at -20 °C for the oxidation of 9,10-dihydroanthracene by [FeIV(O)(TMCS)]+, a complex supported by the tetramethylcyclam (TMC) macrocycle with a tethered thiolate. This KIE value approaches that previously predicted by DFT calculations. Other [FeIV(O)(TMC)(anion)] complexes exhibit values of 20, suggesting that the thiolate ligand of [FeIV(O)(TMCS)]+ plays a unique role in facilitating tunneling. Calculations show that tunneling is most enhanced (a) when the bond asymmetry between C-H bond breaking and O-H bond formation in the transition state is minimized, and (b) when the electrostatic interactions in the O - -H - -C moiety are maximal. These two factors - which peak for the best electron donor, the thiolate ligand - afford a slim and narrow barrier through which the H-atom can tunnel most effectively.",

author = "Johannes Klein and Debasish Mandal and Wei-Min Ching and Dibyendu Mallick and Lawrence Que and Sason Shaik",

note = "Funding Information: This work was supported at the University of Minnesota by grants from the U.S. National Science Foundation (CHE-1361773 and 1665391 to L.Q.), a Feodor Lynen Research Fellowship from the Alexander von Humboldt Foundation to J.E.M.N.K., and a postdoctoral fellowship to W.-M.C. from the Ministry of Science and Technology, Taiwan. S.S. acknowledges support from the Israel Science Foundation (ISF grant 1183/13). Publisher Copyright: {\textcopyright} 2017 American Chemical Society.",

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N2 - An H/D kinetic isotope effect (KIE) of 80 is found at -20 °C for the oxidation of 9,10-dihydroanthracene by [FeIV(O)(TMCS)]+, a complex supported by the tetramethylcyclam (TMC) macrocycle with a tethered thiolate. This KIE value approaches that previously predicted by DFT calculations. Other [FeIV(O)(TMC)(anion)] complexes exhibit values of 20, suggesting that the thiolate ligand of [FeIV(O)(TMCS)]+ plays a unique role in facilitating tunneling. Calculations show that tunneling is most enhanced (a) when the bond asymmetry between C-H bond breaking and O-H bond formation in the transition state is minimized, and (b) when the electrostatic interactions in the O - -H - -C moiety are maximal. These two factors - which peak for the best electron donor, the thiolate ligand - afford a slim and narrow barrier through which the H-atom can tunnel most effectively.

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Privileged Role of Thiolate as the Axial Ligand in Hydrogen Atom Transfer Reactions by Oxoiron(IV) Complexes in Shaping the Potential Energy Surface and Inducing Significant H-Atom Tunneling

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