Transfer Hydrogenation of Ketones Catalyzed by Symmetric Imino-N-heterocyclic Carbene Co(III) Complexes
[Image: see text] The synthesis of new moisture-sensitive imine-functionalized N-heterocyclic carbene (NHC) precursor salts [1-(2-[(hydroxyl-benzylidene)-amino]-ethyl)-3-R-3H-imidazole-1-ium bromide; R = methyl (1a), ethyl (1b), and benzyl (1c)] is reported. Subsequent deprotonation of 1a–c and coor...
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Chemical
Society
2020
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7033672/ https://www.ncbi.nlm.nih.gov/pubmed/32095690 http://dx.doi.org/10.1021/acsomega.9b03181 |
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author | Abubakar, Samaila Bala, Muhammad D. |
author_facet | Abubakar, Samaila Bala, Muhammad D. |
author_sort | Abubakar, Samaila |
collection | PubMed |
description | [Image: see text] The synthesis of new moisture-sensitive imine-functionalized N-heterocyclic carbene (NHC) precursor salts [1-(2-[(hydroxyl-benzylidene)-amino]-ethyl)-3-R-3H-imidazole-1-ium bromide; R = methyl (1a), ethyl (1b), and benzyl (1c)] is reported. Subsequent deprotonation of 1a–c and coordination of the in situ generated NHC ligands to CoBr(2) led to the isolation of air-stable six-coordinate Co(III) complexes 2a–c, respectively. All the salts and complexes were fully characterized. Single-crystal X-ray analysis of 2a and 2c showed octahedral Co centers hexacoordinated to two NHC carbons, two imine nitrogen atoms, and two phenolate oxygens in the form [C^N^O(Co(3+))C^N^O]. The complexes were used in the catalytic transfer hydrogenation (CTH) of a range of ketones in 2-propanol as the solvent and hydrogen donor. Based on a low catalyst concentration of 0.4 mol %, significant conversions in the range of 70–99% were recorded at high turnover frequencies up to 1635 h(–1). A mechanism to account for the steps involved in the CTH of cyclohexanone by complex 2a is proposed and supported by data from cyclic voltammetry, low-resolution mass spectrometry, UV, and IR spectroscopic techniques. |
format | Online Article Text |
id | pubmed-7033672 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2020 |
publisher | American Chemical
Society |
record_format | MEDLINE/PubMed |
spelling | pubmed-70336722020-02-24 Transfer Hydrogenation of Ketones Catalyzed by Symmetric Imino-N-heterocyclic Carbene Co(III) Complexes Abubakar, Samaila Bala, Muhammad D. ACS Omega [Image: see text] The synthesis of new moisture-sensitive imine-functionalized N-heterocyclic carbene (NHC) precursor salts [1-(2-[(hydroxyl-benzylidene)-amino]-ethyl)-3-R-3H-imidazole-1-ium bromide; R = methyl (1a), ethyl (1b), and benzyl (1c)] is reported. Subsequent deprotonation of 1a–c and coordination of the in situ generated NHC ligands to CoBr(2) led to the isolation of air-stable six-coordinate Co(III) complexes 2a–c, respectively. All the salts and complexes were fully characterized. Single-crystal X-ray analysis of 2a and 2c showed octahedral Co centers hexacoordinated to two NHC carbons, two imine nitrogen atoms, and two phenolate oxygens in the form [C^N^O(Co(3+))C^N^O]. The complexes were used in the catalytic transfer hydrogenation (CTH) of a range of ketones in 2-propanol as the solvent and hydrogen donor. Based on a low catalyst concentration of 0.4 mol %, significant conversions in the range of 70–99% were recorded at high turnover frequencies up to 1635 h(–1). A mechanism to account for the steps involved in the CTH of cyclohexanone by complex 2a is proposed and supported by data from cyclic voltammetry, low-resolution mass spectrometry, UV, and IR spectroscopic techniques. American Chemical Society 2020-02-06 /pmc/articles/PMC7033672/ /pubmed/32095690 http://dx.doi.org/10.1021/acsomega.9b03181 Text en Copyright © 2020 American Chemical Society This is an open access article published under an ACS AuthorChoice License (http://pubs.acs.org/page/policy/authorchoice_termsofuse.html) , which permits copying and redistribution of the article or any adaptations for non-commercial purposes. |
spellingShingle | Abubakar, Samaila Bala, Muhammad D. Transfer Hydrogenation of Ketones Catalyzed by Symmetric Imino-N-heterocyclic Carbene Co(III) Complexes |
title | Transfer Hydrogenation
of Ketones Catalyzed by Symmetric
Imino-N-heterocyclic Carbene Co(III) Complexes |
title_full | Transfer Hydrogenation
of Ketones Catalyzed by Symmetric
Imino-N-heterocyclic Carbene Co(III) Complexes |
title_fullStr | Transfer Hydrogenation
of Ketones Catalyzed by Symmetric
Imino-N-heterocyclic Carbene Co(III) Complexes |
title_full_unstemmed | Transfer Hydrogenation
of Ketones Catalyzed by Symmetric
Imino-N-heterocyclic Carbene Co(III) Complexes |
title_short | Transfer Hydrogenation
of Ketones Catalyzed by Symmetric
Imino-N-heterocyclic Carbene Co(III) Complexes |
title_sort | transfer hydrogenation
of ketones catalyzed by symmetric
imino-n-heterocyclic carbene co(iii) complexes |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7033672/ https://www.ncbi.nlm.nih.gov/pubmed/32095690 http://dx.doi.org/10.1021/acsomega.9b03181 |
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