TY - JOUR
T1 - A Highly Reactive Chromium(V)-Oxo TAML Cation Radical Complex in Electron Transfer and Oxygen Atom Transfer Reactions
AU - Hong, Young Hyun
AU - Jang, Yuri
AU - Ezhov, Roman
AU - Seo, Mi Sook
AU - Lee, Yong Min
AU - Pandey, Bhawana
AU - Hong, Seungwoo
AU - Pushkar, Yulia
AU - Fukuzumi, Shunichi
AU - Nam, Wonwoo
N1 - Funding Information:
This work was supported by the NRF of Korea through CRI (NRF-2012R1A3A2048842 to W.N.) and Basic Science Research Program (2020R1I1A1A01074630 to Y.-M.L., 2019R1I1A1A01055822 to M.S.S., and 2020R1A6A3A13072451 to Y.H.H.). This research was also supported by the NSF, CHE-1900476 (Y.P.), and Xi’an Key Laboratory of Organometallic Material Chemistry (W.N.). The use of the Advanced Photon Source, an Office of Science User Facility operated by the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract DE-AC02-06CH11357. The PNC/XSD (Sector 20) facilities at the Advanced Photon Source and research at these facilities were supported by the U.S. Department of Energy, Basic Energy Science, and the Canadian Light Source.
Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/3/5
Y1 - 2021/3/5
N2 - We report the synthesis, characterization, and electron-transfer (ET) oxidation reactivity of a chromium(V)-oxo TAML cation radical complex binding Sc3+ ion, {[CrV(O)(TAML•+)]-Sc3+}3+ (2-Sc). Its precursors, such as [CrV(O)(TAML)]- (1) and {[CrV(O)(TAML)]-Sc3+}2+ (1-Sc), were also characterized spectroscopically and/or structurally. In ET and oxygen atom transfer (OAT) reactions, while 1 and 1-Sc were sluggish oxidants, 2-Sc was a highly reactive oxidant with an extremely small reorganization energy. For example, in ET oxidation reactions, nanosecond laser-induced transient absorption measurements were performed to examine the fast ET from electron donors (e.g., ferrocene derivatives) to 2-Sc, affording a small reorganization energy (λ = 0.26 eV) of ET, which is even much smaller than the λ values reported in the ET reduction of heme Compound I (Cpd I) models and non-heme metal-oxo complexes. Such a small reorganization energy is ascribed to the TAML ligand centered ET reduction of 2-Sc. The λ value of 0.26 eV was also obtained in the electron self-exchange reaction between 2-Sc and 1-Sc. In OAT reactions, the rate constants of the sulfoxidation of thioanisole derivatives by 2-Sc at -40 °C were much greater than those reported in the oxidation of thioanisoles by heme Cpd I and non-heme metal-oxo complexes. The reactivity of 2-Sc in hydrogen atom transfer (HAT) reactions is also discussed briefly. To the best of our knowledge, this Cr(V)-oxo TAML cation radical complex binding Sc3+ ion, {[CrV(O)(TAML•+)]-Sc3+}3+, with an extremely small reorganization energy is one of the most powerful high-valent metal-oxo oxidants in ET and OAT reactions.
AB - We report the synthesis, characterization, and electron-transfer (ET) oxidation reactivity of a chromium(V)-oxo TAML cation radical complex binding Sc3+ ion, {[CrV(O)(TAML•+)]-Sc3+}3+ (2-Sc). Its precursors, such as [CrV(O)(TAML)]- (1) and {[CrV(O)(TAML)]-Sc3+}2+ (1-Sc), were also characterized spectroscopically and/or structurally. In ET and oxygen atom transfer (OAT) reactions, while 1 and 1-Sc were sluggish oxidants, 2-Sc was a highly reactive oxidant with an extremely small reorganization energy. For example, in ET oxidation reactions, nanosecond laser-induced transient absorption measurements were performed to examine the fast ET from electron donors (e.g., ferrocene derivatives) to 2-Sc, affording a small reorganization energy (λ = 0.26 eV) of ET, which is even much smaller than the λ values reported in the ET reduction of heme Compound I (Cpd I) models and non-heme metal-oxo complexes. Such a small reorganization energy is ascribed to the TAML ligand centered ET reduction of 2-Sc. The λ value of 0.26 eV was also obtained in the electron self-exchange reaction between 2-Sc and 1-Sc. In OAT reactions, the rate constants of the sulfoxidation of thioanisole derivatives by 2-Sc at -40 °C were much greater than those reported in the oxidation of thioanisoles by heme Cpd I and non-heme metal-oxo complexes. The reactivity of 2-Sc in hydrogen atom transfer (HAT) reactions is also discussed briefly. To the best of our knowledge, this Cr(V)-oxo TAML cation radical complex binding Sc3+ ion, {[CrV(O)(TAML•+)]-Sc3+}3+, with an extremely small reorganization energy is one of the most powerful high-valent metal-oxo oxidants in ET and OAT reactions.
KW - chromium(V)-oxo complex
KW - electron transfer
KW - oxygen atom transfer
KW - redox-inactive metal ion
KW - reorganization energy
UR - http://www.scopus.com/inward/record.url?scp=85102011639&partnerID=8YFLogxK
U2 - 10.1021/acscatal.1c00079
DO - 10.1021/acscatal.1c00079
M3 - Article
AN - SCOPUS:85102011639
SN - 2155-5435
VL - 11
SP - 2889
EP - 2901
JO - ACS Catalysis
JF - ACS Catalysis
IS - 5
ER -