A Sterically Encumbered Triarylborane Enabling CO2 Reduction to Formate by Electrons and Protons.
- 1Universität Göttingen, Institut für Anorganische Chemie, Tammannstr. 4, 37077Göttingen, Germany.
- 2University of Alberta , Department of Chemistry, 11227 Saskatchewan Dr. NW, Edmonton, AlbertaT6G 2G2, Canada.
Abstract
Borohydrides are widely used sources of hydride ions (H-), but their conventional synthesis from highly reducing metal hydrides is energetically demanding and undermines sustainable applications. Herein, we report a sterically encumbered thioether-substituted triaryl borane, 1,2-(tBuS)C6H4(BMes2) (3) (Mes = 2,4,6-Me3C6H2), which is highly air- and moisture-stable. 3 exhibits a one-electron reduction at E0 = -2.62 V vs Fc+|0 and a radical anion half-lifetime of ∼0.5 s in THF, enabling bimolecular follow-up reactivity. Indeed, two-electron reduction and protonation of 3 with KC8/[DBUH]+ (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene) or hydride transfer from Li(AlH4) affords the borohydride 4-. From a hydricity-potential correlation, we estimate a hydricity of ∼36 kcal mol-1 in MeCN, which allows 4- to reduce H+ to H2 and CO2 to formate under ambient conditions in almost quantitative yields. The reaction of 3, [DBUH]+, KC8, and CO2 furnishes potassium formate in ∼90% spectroscopic yield, establishing a closed synthetic cycle for CO2 reduction by protons and electrons at a boron center. These results highlight how tailor-made, redox-active boranes can complement transition-metal hydrides as modular, metal-free platforms for coupling renewable electrons and protons in CO2 utilization chemistry.
Related
- Reversible dissociation of a sterically distorted dimer of a phosphagermylenylidene
- Visible-light-Enabled O-Selective Radical Etherification of 1,2-Dicarbonyl Compounds for the Synthesis of Sterically Congested Ethers
- Accessing Sterically Congested Benzannulated Cyclic Aryl Ethers via Photoredox Decarboxylative Giese-Type C2-C3 Bond Formation.
- Light-driven metal-free thiocarbonyl – olefin metathesis: a general route to sterically hindered alkenes
- Sterically Shielded Cations Decouple Ion-Exchange Capacity from Water Uptake in Anion Exchange Membranes
BibTeX
@article{meyer2026sterically,
title = {{A Sterically Encumbered Triarylborane Enabling CO2 Reduction to Formate by Electrons and Protons.}},
author = {Felix Meyer and Ludwig Zapf and Eric Rivard and Inke Siewert},
journal = {Inorganic chemistry},
year = {2026},
month = oct,
doi = {10.1021/acs.inorgchem.6c03816},
url = {https://europepmc.org/article/MED/42895390},
note = {CC BY},
}
RIS
TY - JOUR
TI - A Sterically Encumbered Triarylborane Enabling CO2 Reduction to Formate by Electrons and Protons.
AU - Felix Meyer
AU - Ludwig Zapf
AU - Eric Rivard
AU - Inke Siewert
PY - 2026
DA - 2026/10/01
JO - Inorganic chemistry
DO - 10.1021/acs.inorgchem.6c03816
UR - https://europepmc.org/article/MED/42895390
AB - Borohydrides are widely used sources of hydride ions (H-), but their conventional synthesis from highly reducing metal hydrides is energetically demanding and undermines sustainable applications. Herein, we report a sterically encumbered thioether-substituted triaryl borane, 1,2-(tBuS)C6H4(BMes2) (3) (Mes = 2,4,6-Me3C6H2), which is highly air- and moisture-stable. 3 exhibits a one-electron reduction at E0 = -2.62 V vs Fc+|0 and a radical anion half-lifetime of ∼0.5 s in THF, enabling bimolecular follow-up reactivity. Indeed, two-electron reduction and protonation of 3 with KC8/[DBUH]+ (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene) or hydride transfer from Li(AlH4) affords the borohydride 4-. From a hydricity-potential correlation, we estimate a hydricity of ∼36 kcal mol-1 in MeCN, which allows 4- to reduce H+ to H2 and CO2 to formate under ambient conditions in almost quantitative yields. The reaction of 3, [DBUH]+, KC8, and CO2 furnishes potassium formate in ∼90% spectroscopic yield, establishing a closed synthetic cycle for CO2 reduction by protons and electrons at a boron center. These results highlight how tailor-made, redox-active boranes can complement transition-metal hydrides as modular, metal-free platforms for coupling renewable electrons and protons in CO2 utilization chemistry.
SN - 0020-1669
SN - 1520-510X
ER -