Steric and electronic effects in the bonding of N-heterocyclic ligands to transition metals

Cavallo, Luigi; Correa, Andrea; Costabile, Chiara; Jacobsen, Heiko

doi:10.1016/j.jorganchem.2005.07.012

Cited by 444 publications

(228 citation statements)

References 32 publications

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“…The catalyst can then reduce CO 2 to a lower-oxidation-state carbon-based product such as CO and regenerate the initial neutral catalyst. Alternatively, after the first reduction sequence, the catalyst can In addition to a key mechanistic difference during photocatalytic CO2 reduction reactions, NHCligated catalysts have long been heralded as robust, highly reactive systems in general [20][21][22][23]. Concerning photocatalytic CO2 reduction with sunlight, only one catalyst framework has been put forward utilizing an NHC ligand [10].…”

Section: Introductionmentioning

confidence: 99%

A Robust Pyridyl-NHC-Ligated Rhenium Photocatalyst for CO2 Reduction in the Presence of Water and Oxygen

et al. 2018

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Re(pyNHC-PhCF 3 )(CO) 3 Br is a highly active photocatalyst for CO 2 reduction. The PhCF 3 derivative was previously empirically shown to be a robust catalyst. Here, the role of the PhCF 3 group is probed computationally and the robust nature of this catalyst is analyzed with regard to the presence of water and oxygen introduced in controlled amounts during the photocatalytic reduction of CO 2 to CO with visible light. This complex was found to work well from 0-1% water concentration reproducibly; however, trace amounts of water were required for benchmark Re(bpy)(CO) 3 Cl to give reproducible reactivity. When ambient air is added to the reaction mixture, the NHC complex was found to retain substantial performance (~50% of optimized reactivity) at up to 40% ambient atmosphere and 60% CO 2 while the Re(bpy)(CO) 3 Cl complex was found to give a dramatically reduced CO 2 reduction reactivity upon introduction of ambient atmosphere. Through the use of time-correlated single photon counting studies and prior electrochemical results, we reasoned that this enhanced catalyst resilience is due to a mechanistic difference between the NHC-and bpy-based catalysts. These results highlight an important feature of this NHC-ligated catalyst: substantially enhanced stability toward common reaction contaminates.

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Section: Introductionmentioning

confidence: 99%

A Robust Pyridyl-NHC-Ligated Rhenium Photocatalyst for CO2 Reduction in the Presence of Water and Oxygen

et al. 2018

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“…1 Electronically, the NHC ligand has often been considered to be a better σ donor, and a weaker π acceptor, than the phosphine ligand, 2 though contrary evidence regarding their π acceptor ability is available. 3 Relatively simple synthetic procedures leading to precursor imidazolium salts have been elucidated, 4 and many routes that allow the introduction of an NHC ligand to a metal centre have been developed. The reaction of imidazolium salts with silver oxide giving an NHC complex of silver, which serves as a useful trans-metallating reagent, has proved particularly popular, [5][6][7][8] and we use it in this paper.…”

Section: Introductionmentioning

confidence: 99%

Platinum(ii) N-heterocyclic carbene complexes: coordination and cyclometallation.

et al. 2010

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“…77,78 By using SambVca (version 2), it is possible to analyse and visualise the first coordination sphere around the metal where the catalysis takes place. [79][80][81] The quadrants around gold in the IMe and IPr complexes were plotted as steric contour maps (Figure 4). It is evident from Figure 4 that for these two Au complexes, species bearing IPr present significantly more steric bulk.…”

Section: Digold Catalysismentioning

confidence: 99%

The preference for dual-gold(i) catalysis in the hydro(alkoxylation vs. phenoxylation) of alkynes

et al. 2017

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This version is available at https://strathprints.strath.ac.uk/61289/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. Herein we study the hydroalkoxylation and hydrophenoxylation of alkynes using density functional theory calculations, and compare two possible mechanisms that have been proposed previously on the basis of theoretical and experimental studies, which unravel different preferences because of both the nature of the alkyne and alcohol, as well as the non-innocent role of the counter-anion of the dual gold based catalyst. Entropy is found to have a significant effect, rendering the nucleophilic attack of the monoaurated intermediate [Au(L)(η 2 -alkyne)] + difficult both kinetically and thermodynamically; this mechanism cannot easily form only the trans-alkene product that is observed experimentally. Instead, reaction via a dual gold catalysed mechanism presents much lower barriers. In addition, for the sake of direct comparison with recent results by Belanzoni, Zuccaccia, oversimplification of the Nheterocyclic carbene (NHC) ligand in the calculations might decrease the enthalpy barrier and lead to results that are not directly applicable to experiment. Moreover, the alkylic or arylic nature of the alkyne and/or alcohol is also tested. ORGANIC & BIOMOLECULAR CHEMISTRY ARTICLE

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Steric and electronic effects in the bonding of N-heterocyclic ligands to transition metals

Cited by 444 publications

References 32 publications

A Robust Pyridyl-NHC-Ligated Rhenium Photocatalyst for CO2 Reduction in the Presence of Water and Oxygen

A Robust Pyridyl-NHC-Ligated Rhenium Photocatalyst for CO2 Reduction in the Presence of Water and Oxygen

Platinum(ii) N-heterocyclic carbene complexes: coordination and cyclometallation.

The preference for dual-gold(i) catalysis in the hydro(alkoxylation vs. phenoxylation) of alkynes

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