Tetrakis(N-heterocyclic Carbene)-Diboron(0): Double Single-Electron-Transfer Reactivity

Jun Fan; An Ping Koh; Jingsong Zhou; Zheng Feng Zhang; Chi Shiun Wu; Richard D. Webster; Ming Der Su; Cheuk Wai So

doi:10.1021/jacs.3c01801

Tetrakis(N-heterocyclic Carbene)-Diboron(0): Double Single-Electron-Transfer Reactivity

Jun Fan, An Ping Koh, Jingsong Zhou, Zheng Feng Zhang, Chi Shiun Wu, Richard D. Webster^*, Ming Der Su^*, Cheuk Wai So^*

^*Corresponding author for this work

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

10 Citations (Scopus)

Abstract

The use of 1,3,4,5-tetramethylimidazol-2-ylidene (IMe) to coordinate with diatomic B₂species afforded a tetrakis(N-heterocyclic carbene)-diboron(0) [(IMe)₂B-B(IMe)₂] (2). The singly bonded B₂moiety therein possesses a valence electronic configuration 1σ_g²1π_u²1π_g*²with four vacant molecular orbitals (1σ_u*, 2σ_g, 1π_u′, 1π_g′*) coordinated with IMe. Its unprecedented electronic structure is analogous to the energetically unfavorable planar hydrazine with a D_2hsymmetry. The two highly reactive π_g∗ antibonding electrons enable double single-electron-transfer (SET) reactivity in small-molecule activation. Compound 2 underwent a double SET reduction with CO₂to form two carbon dioxide radical anions CO₂^•-, which then reduced pyridine to yield a carboxylated pyridine reductive coupling dianion [O₂CNC₅(H)₅-C₅(H)₅NCO₂]^2-and converted compound 2 to the tetrakis(N-heterocyclic carbene)-diborene dication [(IMe)₂B═B(IMe)₂]²⁺(3²⁺). This is a remarkable transition-metal-free SET reduction of CO₂without ultraviolet/visible (UV/vis) light conditions.

Original language	English
Pages (from-to)	11669-11677
Number of pages	9
Journal	Journal of the American Chemical Society
Volume	145
Issue number	21
DOIs	https://doi.org/10.1021/jacs.3c01801
Publication status	Published - May 31 2023
Externally published	Yes

Bibliographical note

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© 2023 American Chemical Society. All rights reserved.

ASJC Scopus Subject Areas

Catalysis
General Chemistry
Biochemistry
Colloid and Surface Chemistry

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title = "Tetrakis(N-heterocyclic Carbene)-Diboron(0): Double Single-Electron-Transfer Reactivity",

abstract = "The use of 1,3,4,5-tetramethylimidazol-2-ylidene (IMe) to coordinate with diatomic B2species afforded a tetrakis(N-heterocyclic carbene)-diboron(0) [(IMe)2B-B(IMe)2] (2). The singly bonded B2moiety therein possesses a valence electronic configuration 1σg21πu21πg*2with four vacant molecular orbitals (1σu*, 2σg, 1πu′, 1πg′*) coordinated with IMe. Its unprecedented electronic structure is analogous to the energetically unfavorable planar hydrazine with a D2hsymmetry. The two highly reactive πg∗ antibonding electrons enable double single-electron-transfer (SET) reactivity in small-molecule activation. Compound 2 underwent a double SET reduction with CO2to form two carbon dioxide radical anions CO2•-, which then reduced pyridine to yield a carboxylated pyridine reductive coupling dianion [O2CNC5(H)5-C5(H)5NCO2]2-and converted compound 2 to the tetrakis(N-heterocyclic carbene)-diborene dication [(IMe)2B═B(IMe)2]2+(32+). This is a remarkable transition-metal-free SET reduction of CO2without ultraviolet/visible (UV/vis) light conditions.",

author = "Jun Fan and Koh, {An Ping} and Jingsong Zhou and Zhang, {Zheng Feng} and Wu, {Chi Shiun} and Webster, {Richard D.} and Su, {Ming Der} and So, {Cheuk Wai}",

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T2 - Double Single-Electron-Transfer Reactivity

AU - Fan, Jun

AU - Koh, An Ping

AU - Zhou, Jingsong

AU - Zhang, Zheng Feng

AU - Wu, Chi Shiun

AU - Webster, Richard D.

AU - Su, Ming Der

AU - So, Cheuk Wai

PY - 2023/5/31

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AB - The use of 1,3,4,5-tetramethylimidazol-2-ylidene (IMe) to coordinate with diatomic B2species afforded a tetrakis(N-heterocyclic carbene)-diboron(0) [(IMe)2B-B(IMe)2] (2). The singly bonded B2moiety therein possesses a valence electronic configuration 1σg21πu21πg*2with four vacant molecular orbitals (1σu*, 2σg, 1πu′, 1πg′*) coordinated with IMe. Its unprecedented electronic structure is analogous to the energetically unfavorable planar hydrazine with a D2hsymmetry. The two highly reactive πg∗ antibonding electrons enable double single-electron-transfer (SET) reactivity in small-molecule activation. Compound 2 underwent a double SET reduction with CO2to form two carbon dioxide radical anions CO2•-, which then reduced pyridine to yield a carboxylated pyridine reductive coupling dianion [O2CNC5(H)5-C5(H)5NCO2]2-and converted compound 2 to the tetrakis(N-heterocyclic carbene)-diborene dication [(IMe)2B═B(IMe)2]2+(32+). This is a remarkable transition-metal-free SET reduction of CO2without ultraviolet/visible (UV/vis) light conditions.

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Tetrakis(N-heterocyclic Carbene)-Diboron(0): Double Single-Electron-Transfer Reactivity

Abstract

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