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Geometrical influence on the non-biomimetic heterolytic splitting of H(2) by bio-inspired [FeFe]-hydrogenase complexes: a rare example of inverted frustrated Lewis pair based reactivity

Despite the high levels of interest in the synthesis of bio-inspired [FeFe]-hydrogenase complexes, H(2) oxidation, which is one specific aspect of hydrogenase enzymatic activity, is not observed for most reported complexes. To attempt H–H bond cleavage, two disubstituted diiron dithiolate complexes...

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Autores principales: Chatelain, Lucile, Breton, Jean-Baptiste, Arrigoni, Federica, Schollhammer, Philippe, Zampella, Giuseppe
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society of Chemistry 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9067592/
https://www.ncbi.nlm.nih.gov/pubmed/35655865
http://dx.doi.org/10.1039/d1sc06975f
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author Chatelain, Lucile
Breton, Jean-Baptiste
Arrigoni, Federica
Schollhammer, Philippe
Zampella, Giuseppe
author_facet Chatelain, Lucile
Breton, Jean-Baptiste
Arrigoni, Federica
Schollhammer, Philippe
Zampella, Giuseppe
author_sort Chatelain, Lucile
collection PubMed
description Despite the high levels of interest in the synthesis of bio-inspired [FeFe]-hydrogenase complexes, H(2) oxidation, which is one specific aspect of hydrogenase enzymatic activity, is not observed for most reported complexes. To attempt H–H bond cleavage, two disubstituted diiron dithiolate complexes in the form of [Fe(2)(μ-pdt)L(2)(CO)(4)] (L: PMe(3), dmpe) have been used to play the non-biomimetic role of a Lewis base, with frustrated Lewis pairs (FLPs) formed in the presence of B(C(6)F(5))(3) Lewis acid. These unprecedented FLPs, based on the bimetallic Lewis base partner, allow the heterolytic splitting of the H(2) molecule, forming a protonated diiron cation and hydrido-borate anion. The substitution, symmetrical or asymmetrical, of two phosphine ligands at the diiron dithiolate core induces a strong difference in the H(2) bond cleavage abilities, with the FLP based on the first complex being more efficient than the second. DFT investigations examined the different mechanistic pathways involving each accessible isomer and rationalized the experimental findings. One of the main DFT results highlights that the iron site acting as a Lewis base for the asymmetrical complex is the {Fe(CO)(3)} subunit, which is less electron-rich than the {FeL(CO)(2)} site of the symmetrical complex, diminishing the reactivity towards H(2). Calculations relating to the different mechanistic pathways revealed the presence of a terminal hydride intermediate at the apical site of a rotated {Fe(CO)(3)} site, which is experimentally observed, and a semi-bridging hydride intermediate from H(2) activation at the Fe–Fe site; these are responsible for a favourable back-reaction, reducing the conversion yield observed in the case of the asymmetrical complex. The use of two equivalents of Lewis acid allows for more complete and faster H(2) bond cleavage due to the encapsulation of the hydrido-borate species by a second borane, favouring the reactivity of each FLP, in agreement with DFT calculations.
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spelling pubmed-90675922022-06-01 Geometrical influence on the non-biomimetic heterolytic splitting of H(2) by bio-inspired [FeFe]-hydrogenase complexes: a rare example of inverted frustrated Lewis pair based reactivity Chatelain, Lucile Breton, Jean-Baptiste Arrigoni, Federica Schollhammer, Philippe Zampella, Giuseppe Chem Sci Chemistry Despite the high levels of interest in the synthesis of bio-inspired [FeFe]-hydrogenase complexes, H(2) oxidation, which is one specific aspect of hydrogenase enzymatic activity, is not observed for most reported complexes. To attempt H–H bond cleavage, two disubstituted diiron dithiolate complexes in the form of [Fe(2)(μ-pdt)L(2)(CO)(4)] (L: PMe(3), dmpe) have been used to play the non-biomimetic role of a Lewis base, with frustrated Lewis pairs (FLPs) formed in the presence of B(C(6)F(5))(3) Lewis acid. These unprecedented FLPs, based on the bimetallic Lewis base partner, allow the heterolytic splitting of the H(2) molecule, forming a protonated diiron cation and hydrido-borate anion. The substitution, symmetrical or asymmetrical, of two phosphine ligands at the diiron dithiolate core induces a strong difference in the H(2) bond cleavage abilities, with the FLP based on the first complex being more efficient than the second. DFT investigations examined the different mechanistic pathways involving each accessible isomer and rationalized the experimental findings. One of the main DFT results highlights that the iron site acting as a Lewis base for the asymmetrical complex is the {Fe(CO)(3)} subunit, which is less electron-rich than the {FeL(CO)(2)} site of the symmetrical complex, diminishing the reactivity towards H(2). Calculations relating to the different mechanistic pathways revealed the presence of a terminal hydride intermediate at the apical site of a rotated {Fe(CO)(3)} site, which is experimentally observed, and a semi-bridging hydride intermediate from H(2) activation at the Fe–Fe site; these are responsible for a favourable back-reaction, reducing the conversion yield observed in the case of the asymmetrical complex. The use of two equivalents of Lewis acid allows for more complete and faster H(2) bond cleavage due to the encapsulation of the hydrido-borate species by a second borane, favouring the reactivity of each FLP, in agreement with DFT calculations. The Royal Society of Chemistry 2022-03-22 /pmc/articles/PMC9067592/ /pubmed/35655865 http://dx.doi.org/10.1039/d1sc06975f Text en This journal is © The Royal Society of Chemistry https://creativecommons.org/licenses/by-nc/3.0/
spellingShingle Chemistry
Chatelain, Lucile
Breton, Jean-Baptiste
Arrigoni, Federica
Schollhammer, Philippe
Zampella, Giuseppe
Geometrical influence on the non-biomimetic heterolytic splitting of H(2) by bio-inspired [FeFe]-hydrogenase complexes: a rare example of inverted frustrated Lewis pair based reactivity
title Geometrical influence on the non-biomimetic heterolytic splitting of H(2) by bio-inspired [FeFe]-hydrogenase complexes: a rare example of inverted frustrated Lewis pair based reactivity
title_full Geometrical influence on the non-biomimetic heterolytic splitting of H(2) by bio-inspired [FeFe]-hydrogenase complexes: a rare example of inverted frustrated Lewis pair based reactivity
title_fullStr Geometrical influence on the non-biomimetic heterolytic splitting of H(2) by bio-inspired [FeFe]-hydrogenase complexes: a rare example of inverted frustrated Lewis pair based reactivity
title_full_unstemmed Geometrical influence on the non-biomimetic heterolytic splitting of H(2) by bio-inspired [FeFe]-hydrogenase complexes: a rare example of inverted frustrated Lewis pair based reactivity
title_short Geometrical influence on the non-biomimetic heterolytic splitting of H(2) by bio-inspired [FeFe]-hydrogenase complexes: a rare example of inverted frustrated Lewis pair based reactivity
title_sort geometrical influence on the non-biomimetic heterolytic splitting of h(2) by bio-inspired [fefe]-hydrogenase complexes: a rare example of inverted frustrated lewis pair based reactivity
topic Chemistry
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9067592/
https://www.ncbi.nlm.nih.gov/pubmed/35655865
http://dx.doi.org/10.1039/d1sc06975f
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