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Coinage metal aluminyl complexes: probing regiochemistry and mechanism in the insertion and reduction of carbon dioxide

The synthesis of coinage metal aluminyl complexes, featuring M–Al covalent bonds, is reported via a salt metathesis approach employing an anionic Al(i) (‘aluminyl’) nucleophile and group 11 electrophiles. This approach allows access to both bimetallic (1 : 1) systems of the type ((t)Bu(3)P)MAl(NON)...

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Autores principales: McManus, Caitilín, Hicks, Jamie, Cui, Xianlu, Zhao, Lili, Frenking, Gernot, Goicoechea, Jose M., Aldridge, Simon
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society of Chemistry 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8528051/
https://www.ncbi.nlm.nih.gov/pubmed/34777765
http://dx.doi.org/10.1039/d1sc04676d
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author McManus, Caitilín
Hicks, Jamie
Cui, Xianlu
Zhao, Lili
Frenking, Gernot
Goicoechea, Jose M.
Aldridge, Simon
author_facet McManus, Caitilín
Hicks, Jamie
Cui, Xianlu
Zhao, Lili
Frenking, Gernot
Goicoechea, Jose M.
Aldridge, Simon
author_sort McManus, Caitilín
collection PubMed
description The synthesis of coinage metal aluminyl complexes, featuring M–Al covalent bonds, is reported via a salt metathesis approach employing an anionic Al(i) (‘aluminyl’) nucleophile and group 11 electrophiles. This approach allows access to both bimetallic (1 : 1) systems of the type ((t)Bu(3)P)MAl(NON) (M = Cu, Ag, Au; NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene) and a 2 : 1 di(aluminyl)cuprate system, K[Cu{Al(NON)}(2)]. The bimetallic complexes readily insert heteroallenes (CO(2), carbodiimides) into the unsupported M–Al bonds to give systems containing a M(CE(2))Al bridging unit (E = O, NR), with the μ-κ(1)(C):κ(2)(E,E′) mode of heteroallene binding being demonstrated crystallographically for carbodiimide insertion in the cases of all three metals, Cu, Ag and Au. The regiochemistry of these processes, leading to the formation of M–C bonds, is rationalized computationally, and is consistent with addition of CO(2) across the M–Al covalent bond with the group 11 metal acting as the nucleophilic partner and Al as the electrophile. While the products of carbodiimide insertion are stable to further reaction, their CO(2) analogues have the potential to react further, depending on the identity of the group 11 metal. ((t)Bu(3)P)Au(CO)(2)Al(NON) is inert to further reaction, but its silver counterpart reacts slowly with CO(2) to give the corresponding carbonate complex (and CO), and the copper system proceeds rapidly to the carbonate even at low temperatures. Experimental and quantum chemical investigations of the mechanism of the CO(2) to CO/carbonate transformation are consistent with rate-determining extrusion of CO from the initially-formed M(CO)(2)Al fragment to give a bimetallic oxide that rapidly assimilates a second molecule of CO(2). The calculated energetic barriers for the most feasible CO extrusion step (ΔG(‡) = 26.6, 33.1, 44.5 kcal mol(−1) for M = Cu, Ag and Au, respectively) are consistent not only with the observed experimental labilities of the respective M(CO)(2)Al motifs, but also with the opposing trends in M–C (increasing) and M–O bond strengths (decreasing) on transitioning from Cu to Au.
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spelling pubmed-85280512021-11-12 Coinage metal aluminyl complexes: probing regiochemistry and mechanism in the insertion and reduction of carbon dioxide McManus, Caitilín Hicks, Jamie Cui, Xianlu Zhao, Lili Frenking, Gernot Goicoechea, Jose M. Aldridge, Simon Chem Sci Chemistry The synthesis of coinage metal aluminyl complexes, featuring M–Al covalent bonds, is reported via a salt metathesis approach employing an anionic Al(i) (‘aluminyl’) nucleophile and group 11 electrophiles. This approach allows access to both bimetallic (1 : 1) systems of the type ((t)Bu(3)P)MAl(NON) (M = Cu, Ag, Au; NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene) and a 2 : 1 di(aluminyl)cuprate system, K[Cu{Al(NON)}(2)]. The bimetallic complexes readily insert heteroallenes (CO(2), carbodiimides) into the unsupported M–Al bonds to give systems containing a M(CE(2))Al bridging unit (E = O, NR), with the μ-κ(1)(C):κ(2)(E,E′) mode of heteroallene binding being demonstrated crystallographically for carbodiimide insertion in the cases of all three metals, Cu, Ag and Au. The regiochemistry of these processes, leading to the formation of M–C bonds, is rationalized computationally, and is consistent with addition of CO(2) across the M–Al covalent bond with the group 11 metal acting as the nucleophilic partner and Al as the electrophile. While the products of carbodiimide insertion are stable to further reaction, their CO(2) analogues have the potential to react further, depending on the identity of the group 11 metal. ((t)Bu(3)P)Au(CO)(2)Al(NON) is inert to further reaction, but its silver counterpart reacts slowly with CO(2) to give the corresponding carbonate complex (and CO), and the copper system proceeds rapidly to the carbonate even at low temperatures. Experimental and quantum chemical investigations of the mechanism of the CO(2) to CO/carbonate transformation are consistent with rate-determining extrusion of CO from the initially-formed M(CO)(2)Al fragment to give a bimetallic oxide that rapidly assimilates a second molecule of CO(2). The calculated energetic barriers for the most feasible CO extrusion step (ΔG(‡) = 26.6, 33.1, 44.5 kcal mol(−1) for M = Cu, Ag and Au, respectively) are consistent not only with the observed experimental labilities of the respective M(CO)(2)Al motifs, but also with the opposing trends in M–C (increasing) and M–O bond strengths (decreasing) on transitioning from Cu to Au. The Royal Society of Chemistry 2021-09-16 /pmc/articles/PMC8528051/ /pubmed/34777765 http://dx.doi.org/10.1039/d1sc04676d Text en This journal is © The Royal Society of Chemistry https://creativecommons.org/licenses/by/3.0/
spellingShingle Chemistry
McManus, Caitilín
Hicks, Jamie
Cui, Xianlu
Zhao, Lili
Frenking, Gernot
Goicoechea, Jose M.
Aldridge, Simon
Coinage metal aluminyl complexes: probing regiochemistry and mechanism in the insertion and reduction of carbon dioxide
title Coinage metal aluminyl complexes: probing regiochemistry and mechanism in the insertion and reduction of carbon dioxide
title_full Coinage metal aluminyl complexes: probing regiochemistry and mechanism in the insertion and reduction of carbon dioxide
title_fullStr Coinage metal aluminyl complexes: probing regiochemistry and mechanism in the insertion and reduction of carbon dioxide
title_full_unstemmed Coinage metal aluminyl complexes: probing regiochemistry and mechanism in the insertion and reduction of carbon dioxide
title_short Coinage metal aluminyl complexes: probing regiochemistry and mechanism in the insertion and reduction of carbon dioxide
title_sort coinage metal aluminyl complexes: probing regiochemistry and mechanism in the insertion and reduction of carbon dioxide
topic Chemistry
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8528051/
https://www.ncbi.nlm.nih.gov/pubmed/34777765
http://dx.doi.org/10.1039/d1sc04676d
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