A Thiourea Tether in the Second Coordination Sphere as a Binding Site for CO2 and a Proton Donor Promotes the Electrochemical Reduction of CO2 to CO Catalyzed by a Rhenium Bipyridine-Type Complex

Eynat Haviv, Dima Azaiza-Dabbah, Raanan Carmieli, Liat Avram, Jan M.L. Martin, Ronny Neumann

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The electrochemical reduction of CO2 has been extensively investigated in recent years, with the expectation that a detailed mechanistic understanding could achieve the goal of finding a stable catalyst with high turnover frequencies and low reduction potentials. In the catalytic cycle of the carbon dioxide hydrogenase enzyme, it has been suggested that the reduced metal center reacts with CO2 to form a carboxylate intermediate that is stabilized by hydrogen bonding using a histidine moiety in the second coordination sphere. Using the well-known fac-Re(I)bipyridine(CO)3Cl complex as a starting point, the bipyridine ligand was modified in the second coordination sphere with a thiourea tether that is known to form hydrogen bonds with carbonyl moieties. The resulting Re(I) catalyst was an excellent electrocatalyst for the selective reduction of CO2 to CO, with a turnover frequency of 3040 s-1. The binding of CO2 to the thiourea tether was observable by 1H NMR, and NOE experiments showed that the hydrogen atoms of the thiourea group were labile. Further experiments indicated that the thiourea moiety is also a local proton source and addition of an external proton source actually inhibits catalysis. The absence of a kinetic isotope effect was explained through DFT calculations that showed that the proton invariably jumps to the nearest CO2 oxygen atom to form a metal-carboxylic acid without going through any minimum or transition state. EPR and NMR spectroscopies were used to identify the various reduced intermediates. Thus, the thiourea tether in the second coordination sphere can bind CO2, stabilize carboxylic acid reaction intermediates, and directly act as a local proton source, leading to a significantly more active catalyst.

Original languageEnglish
Pages (from-to)12451-12456
Number of pages6
JournalJournal of the American Chemical Society
Volume140
Issue number39
DOIs
Publication statusPublished - Oct 3 2018

Fingerprint

Rhenium
Thiourea
Thioureas
Binding sites
Carbon Monoxide
Protons
Binding Sites
Carboxylic Acids
Carboxylic acids
Catalysts
Hydrogen
Hydrogen bonds
Metals
Hydrogenase
Reaction intermediates
Atoms
Electrocatalysts
Hydrogen Bonding
Catalysis
Histidine

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

A Thiourea Tether in the Second Coordination Sphere as a Binding Site for CO2 and a Proton Donor Promotes the Electrochemical Reduction of CO2 to CO Catalyzed by a Rhenium Bipyridine-Type Complex. / Haviv, Eynat; Azaiza-Dabbah, Dima; Carmieli, Raanan; Avram, Liat; Martin, Jan M.L.; Neumann, Ronny.

In: Journal of the American Chemical Society, Vol. 140, No. 39, 03.10.2018, p. 12451-12456.

Research output: Contribution to journalArticle

@article{47a47bdf54954e2faf06955339eafb66,
title = "A Thiourea Tether in the Second Coordination Sphere as a Binding Site for CO2 and a Proton Donor Promotes the Electrochemical Reduction of CO2 to CO Catalyzed by a Rhenium Bipyridine-Type Complex",
abstract = "The electrochemical reduction of CO2 has been extensively investigated in recent years, with the expectation that a detailed mechanistic understanding could achieve the goal of finding a stable catalyst with high turnover frequencies and low reduction potentials. In the catalytic cycle of the carbon dioxide hydrogenase enzyme, it has been suggested that the reduced metal center reacts with CO2 to form a carboxylate intermediate that is stabilized by hydrogen bonding using a histidine moiety in the second coordination sphere. Using the well-known fac-Re(I)bipyridine(CO)3Cl complex as a starting point, the bipyridine ligand was modified in the second coordination sphere with a thiourea tether that is known to form hydrogen bonds with carbonyl moieties. The resulting Re(I) catalyst was an excellent electrocatalyst for the selective reduction of CO2 to CO, with a turnover frequency of 3040 s-1. The binding of CO2 to the thiourea tether was observable by 1H NMR, and NOE experiments showed that the hydrogen atoms of the thiourea group were labile. Further experiments indicated that the thiourea moiety is also a local proton source and addition of an external proton source actually inhibits catalysis. The absence of a kinetic isotope effect was explained through DFT calculations that showed that the proton invariably jumps to the nearest CO2 oxygen atom to form a metal-carboxylic acid without going through any minimum or transition state. EPR and NMR spectroscopies were used to identify the various reduced intermediates. Thus, the thiourea tether in the second coordination sphere can bind CO2, stabilize carboxylic acid reaction intermediates, and directly act as a local proton source, leading to a significantly more active catalyst.",
author = "Eynat Haviv and Dima Azaiza-Dabbah and Raanan Carmieli and Liat Avram and Martin, {Jan M.L.} and Ronny Neumann",
year = "2018",
month = "10",
day = "3",
doi = "10.1021/jacs.8b05658",
language = "English",
volume = "140",
pages = "12451--12456",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "39",

}

TY - JOUR

T1 - A Thiourea Tether in the Second Coordination Sphere as a Binding Site for CO2 and a Proton Donor Promotes the Electrochemical Reduction of CO2 to CO Catalyzed by a Rhenium Bipyridine-Type Complex

AU - Haviv, Eynat

AU - Azaiza-Dabbah, Dima

AU - Carmieli, Raanan

AU - Avram, Liat

AU - Martin, Jan M.L.

AU - Neumann, Ronny

PY - 2018/10/3

Y1 - 2018/10/3

N2 - The electrochemical reduction of CO2 has been extensively investigated in recent years, with the expectation that a detailed mechanistic understanding could achieve the goal of finding a stable catalyst with high turnover frequencies and low reduction potentials. In the catalytic cycle of the carbon dioxide hydrogenase enzyme, it has been suggested that the reduced metal center reacts with CO2 to form a carboxylate intermediate that is stabilized by hydrogen bonding using a histidine moiety in the second coordination sphere. Using the well-known fac-Re(I)bipyridine(CO)3Cl complex as a starting point, the bipyridine ligand was modified in the second coordination sphere with a thiourea tether that is known to form hydrogen bonds with carbonyl moieties. The resulting Re(I) catalyst was an excellent electrocatalyst for the selective reduction of CO2 to CO, with a turnover frequency of 3040 s-1. The binding of CO2 to the thiourea tether was observable by 1H NMR, and NOE experiments showed that the hydrogen atoms of the thiourea group were labile. Further experiments indicated that the thiourea moiety is also a local proton source and addition of an external proton source actually inhibits catalysis. The absence of a kinetic isotope effect was explained through DFT calculations that showed that the proton invariably jumps to the nearest CO2 oxygen atom to form a metal-carboxylic acid without going through any minimum or transition state. EPR and NMR spectroscopies were used to identify the various reduced intermediates. Thus, the thiourea tether in the second coordination sphere can bind CO2, stabilize carboxylic acid reaction intermediates, and directly act as a local proton source, leading to a significantly more active catalyst.

AB - The electrochemical reduction of CO2 has been extensively investigated in recent years, with the expectation that a detailed mechanistic understanding could achieve the goal of finding a stable catalyst with high turnover frequencies and low reduction potentials. In the catalytic cycle of the carbon dioxide hydrogenase enzyme, it has been suggested that the reduced metal center reacts with CO2 to form a carboxylate intermediate that is stabilized by hydrogen bonding using a histidine moiety in the second coordination sphere. Using the well-known fac-Re(I)bipyridine(CO)3Cl complex as a starting point, the bipyridine ligand was modified in the second coordination sphere with a thiourea tether that is known to form hydrogen bonds with carbonyl moieties. The resulting Re(I) catalyst was an excellent electrocatalyst for the selective reduction of CO2 to CO, with a turnover frequency of 3040 s-1. The binding of CO2 to the thiourea tether was observable by 1H NMR, and NOE experiments showed that the hydrogen atoms of the thiourea group were labile. Further experiments indicated that the thiourea moiety is also a local proton source and addition of an external proton source actually inhibits catalysis. The absence of a kinetic isotope effect was explained through DFT calculations that showed that the proton invariably jumps to the nearest CO2 oxygen atom to form a metal-carboxylic acid without going through any minimum or transition state. EPR and NMR spectroscopies were used to identify the various reduced intermediates. Thus, the thiourea tether in the second coordination sphere can bind CO2, stabilize carboxylic acid reaction intermediates, and directly act as a local proton source, leading to a significantly more active catalyst.

UR - http://www.scopus.com/inward/record.url?scp=85053847438&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85053847438&partnerID=8YFLogxK

U2 - 10.1021/jacs.8b05658

DO - 10.1021/jacs.8b05658

M3 - Article

C2 - 30207468

AN - SCOPUS:85053847438

VL - 140

SP - 12451

EP - 12456

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 39

ER -