Importance of the Reactant-State Potentials of Chromium(V)-Oxo Complexes to Determine the Reactivity in Hydrogen-Atom Transfer Reactions

Hiroaki Kotani, Suzue Kaida, Tomoya Ishizuka, Kaoru Mieda, Miyuki Sakaguchi, Takashi Ogura, Yoshihito Shiota, Kazunari Yoshizawa, Takahiko Kojima

Research output: Contribution to journalArticle

Abstract

A new chromium(V)-oxo complex, [Cr V (O)(6-COO - -py-tacn)] 2+ (1; 6-COO - -py-tacn = 1-(6-carboxylato-2-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane), was synthesized and characterized to evaluate the reactivity of Cr V (O) complexes in a hydrogen-atom transfer (HAT) reaction by comparing it with that of a previously reported Cr V (O) complex, [Cr V (O)(6-COO - -tpa)] 2+ (2; 6-COO - -tpa = N,N-bis(2-pyridylmethyl)-N-(6-carboxylato-2-pyridylmethyl)amine). Definitive differences of these two Cr V (O) complexes were observed in resonance Raman scatterings of the Cr-O bond (ν = 911 cm -1 for 1 and 951 cm -1 for 2) and the reduction potential (0.73 V vs SCE for 1 and 1.23 V for 2); this difference should be derived from that of the ligand bound at the trans position to the oxo ligand, a tertiary amino group in 1, and a pyridine nitrogen in 2. When we employed 9,10-dihydroanthracene as a substrate, the second-order rate constant (k) of 1 was 4000 times smaller than that of 2. Plots of normalized k values for both complexes relative to bond dissociation energies (BDEs) of C-H bonds to be cleaved in several substrates showed a pair of parallel lines with slopes of -0.91 for 1 and -0.62 for 2, indicating that the HAT reactions by the two complexes proceed via almost the same transition states. Judging from estimated BDEs of Cr IV (OH)/Cr V (O) (85-87 kcal mol -1 for 1 and 92-94 kcal mol -1 for 2) and the activation barrier in the HAT reaction of DHA (E a = 7.9 kcal mol -1 for 1 and E a = 4.8 kcal mol -1 for 2), the reactivity of Cr V (O) complexes in HAT reactions depends on the energy level of the reactant state rather than the product state.

Original languageEnglish
Pages (from-to)13929-13936
Number of pages8
JournalInorganic Chemistry
Volume57
Issue number21
DOIs
Publication statusPublished - Nov 5 2018

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Chromium
Hydrogen
chromium
hydrogen atoms
reactivity
Atoms
dissociation
Ligands
ligands
resonance scattering
Substrates
Electron energy levels
Amines
Raman scattering
Rate constants
pyridines
amines
Nitrogen
plots
energy levels

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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Importance of the Reactant-State Potentials of Chromium(V)-Oxo Complexes to Determine the Reactivity in Hydrogen-Atom Transfer Reactions. / Kotani, Hiroaki; Kaida, Suzue; Ishizuka, Tomoya; Mieda, Kaoru; Sakaguchi, Miyuki; Ogura, Takashi; Shiota, Yoshihito; Yoshizawa, Kazunari; Kojima, Takahiko.

In: Inorganic Chemistry, Vol. 57, No. 21, 05.11.2018, p. 13929-13936.

Research output: Contribution to journalArticle

Kotani, Hiroaki ; Kaida, Suzue ; Ishizuka, Tomoya ; Mieda, Kaoru ; Sakaguchi, Miyuki ; Ogura, Takashi ; Shiota, Yoshihito ; Yoshizawa, Kazunari ; Kojima, Takahiko. / Importance of the Reactant-State Potentials of Chromium(V)-Oxo Complexes to Determine the Reactivity in Hydrogen-Atom Transfer Reactions. In: Inorganic Chemistry. 2018 ; Vol. 57, No. 21. pp. 13929-13936.
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abstract = "A new chromium(V)-oxo complex, [Cr V (O)(6-COO - -py-tacn)] 2+ (1; 6-COO - -py-tacn = 1-(6-carboxylato-2-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane), was synthesized and characterized to evaluate the reactivity of Cr V (O) complexes in a hydrogen-atom transfer (HAT) reaction by comparing it with that of a previously reported Cr V (O) complex, [Cr V (O)(6-COO - -tpa)] 2+ (2; 6-COO - -tpa = N,N-bis(2-pyridylmethyl)-N-(6-carboxylato-2-pyridylmethyl)amine). Definitive differences of these two Cr V (O) complexes were observed in resonance Raman scatterings of the Cr-O bond (ν = 911 cm -1 for 1 and 951 cm -1 for 2) and the reduction potential (0.73 V vs SCE for 1 and 1.23 V for 2); this difference should be derived from that of the ligand bound at the trans position to the oxo ligand, a tertiary amino group in 1, and a pyridine nitrogen in 2. When we employed 9,10-dihydroanthracene as a substrate, the second-order rate constant (k) of 1 was 4000 times smaller than that of 2. Plots of normalized k values for both complexes relative to bond dissociation energies (BDEs) of C-H bonds to be cleaved in several substrates showed a pair of parallel lines with slopes of -0.91 for 1 and -0.62 for 2, indicating that the HAT reactions by the two complexes proceed via almost the same transition states. Judging from estimated BDEs of Cr IV (OH)/Cr V (O) (85-87 kcal mol -1 for 1 and 92-94 kcal mol -1 for 2) and the activation barrier in the HAT reaction of DHA (E a = 7.9 kcal mol -1 for 1 and E a = 4.8 kcal mol -1 for 2), the reactivity of Cr V (O) complexes in HAT reactions depends on the energy level of the reactant state rather than the product state.",
author = "Hiroaki Kotani and Suzue Kaida and Tomoya Ishizuka and Kaoru Mieda and Miyuki Sakaguchi and Takashi Ogura and Yoshihito Shiota and Kazunari Yoshizawa and Takahiko Kojima",
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T1 - Importance of the Reactant-State Potentials of Chromium(V)-Oxo Complexes to Determine the Reactivity in Hydrogen-Atom Transfer Reactions

AU - Kotani, Hiroaki

AU - Kaida, Suzue

AU - Ishizuka, Tomoya

AU - Mieda, Kaoru

AU - Sakaguchi, Miyuki

AU - Ogura, Takashi

AU - Shiota, Yoshihito

AU - Yoshizawa, Kazunari

AU - Kojima, Takahiko

PY - 2018/11/5

Y1 - 2018/11/5

N2 - A new chromium(V)-oxo complex, [Cr V (O)(6-COO - -py-tacn)] 2+ (1; 6-COO - -py-tacn = 1-(6-carboxylato-2-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane), was synthesized and characterized to evaluate the reactivity of Cr V (O) complexes in a hydrogen-atom transfer (HAT) reaction by comparing it with that of a previously reported Cr V (O) complex, [Cr V (O)(6-COO - -tpa)] 2+ (2; 6-COO - -tpa = N,N-bis(2-pyridylmethyl)-N-(6-carboxylato-2-pyridylmethyl)amine). Definitive differences of these two Cr V (O) complexes were observed in resonance Raman scatterings of the Cr-O bond (ν = 911 cm -1 for 1 and 951 cm -1 for 2) and the reduction potential (0.73 V vs SCE for 1 and 1.23 V for 2); this difference should be derived from that of the ligand bound at the trans position to the oxo ligand, a tertiary amino group in 1, and a pyridine nitrogen in 2. When we employed 9,10-dihydroanthracene as a substrate, the second-order rate constant (k) of 1 was 4000 times smaller than that of 2. Plots of normalized k values for both complexes relative to bond dissociation energies (BDEs) of C-H bonds to be cleaved in several substrates showed a pair of parallel lines with slopes of -0.91 for 1 and -0.62 for 2, indicating that the HAT reactions by the two complexes proceed via almost the same transition states. Judging from estimated BDEs of Cr IV (OH)/Cr V (O) (85-87 kcal mol -1 for 1 and 92-94 kcal mol -1 for 2) and the activation barrier in the HAT reaction of DHA (E a = 7.9 kcal mol -1 for 1 and E a = 4.8 kcal mol -1 for 2), the reactivity of Cr V (O) complexes in HAT reactions depends on the energy level of the reactant state rather than the product state.

AB - A new chromium(V)-oxo complex, [Cr V (O)(6-COO - -py-tacn)] 2+ (1; 6-COO - -py-tacn = 1-(6-carboxylato-2-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane), was synthesized and characterized to evaluate the reactivity of Cr V (O) complexes in a hydrogen-atom transfer (HAT) reaction by comparing it with that of a previously reported Cr V (O) complex, [Cr V (O)(6-COO - -tpa)] 2+ (2; 6-COO - -tpa = N,N-bis(2-pyridylmethyl)-N-(6-carboxylato-2-pyridylmethyl)amine). Definitive differences of these two Cr V (O) complexes were observed in resonance Raman scatterings of the Cr-O bond (ν = 911 cm -1 for 1 and 951 cm -1 for 2) and the reduction potential (0.73 V vs SCE for 1 and 1.23 V for 2); this difference should be derived from that of the ligand bound at the trans position to the oxo ligand, a tertiary amino group in 1, and a pyridine nitrogen in 2. When we employed 9,10-dihydroanthracene as a substrate, the second-order rate constant (k) of 1 was 4000 times smaller than that of 2. Plots of normalized k values for both complexes relative to bond dissociation energies (BDEs) of C-H bonds to be cleaved in several substrates showed a pair of parallel lines with slopes of -0.91 for 1 and -0.62 for 2, indicating that the HAT reactions by the two complexes proceed via almost the same transition states. Judging from estimated BDEs of Cr IV (OH)/Cr V (O) (85-87 kcal mol -1 for 1 and 92-94 kcal mol -1 for 2) and the activation barrier in the HAT reaction of DHA (E a = 7.9 kcal mol -1 for 1 and E a = 4.8 kcal mol -1 for 2), the reactivity of Cr V (O) complexes in HAT reactions depends on the energy level of the reactant state rather than the product state.

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