Indenyl Effect Due to Metal Slippage? Computational Exploration of Rhodium‐Catalyzed Acetylene [2+2+2] Cyclotrimerization

Orian, Laura; Swart, Marcel; Bickelhaupt, F. Matthias

doi:10.1002/cphc.201300934

Cited by 35 publications

(54 citation statements)

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“…An extension to group 9 elements, in particular to Rh, was initially proposed by Booth et al [23] and Ingrosso et al [24] They used numerous different Rh(I) half-sandwich complexes to investigate how to trim and optimize selectivity and the overall cyclotrimerization yield. [10,25,26] The catalytic use of CpM fragments in acetylene [2 + 2 + 2] cyclotrimerization to benzene and alkyne/nitrile [2 + 2 + 2] cycloaddition to pyridine has been investigated also in silico for different metals: Co, [27,28] Rh, [10,29] Ir, [30,31] Ru. [10,25,26] The catalytic use of CpM fragments in acetylene [2 + 2 + 2] cyclotrimerization to benzene and alkyne/nitrile [2 + 2 + 2] cycloaddition to pyridine has been investigated also in silico for different metals: Co, [27,28] Rh, [10,29] Ir, [30,31] Ru.…”

Section: Introductionmentioning

confidence: 99%

Group 9 Metallacyclopentadienes as Key Intermediates in [2+2+2] Alkyne Cyclotrimerizations. Insight from Activation Strain Analyses

2018

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The intramolecular oxidative coupling converting a bis-acetylene complex of formula CpM (C H ) (Cp=C H ; M=Co, Rh, Ir) into a 16-electron metallacycle is studied in silico. This reaction is paradigmatic in acetylene [2+2+2] cycloaddition to benzene catalyzed by CpM fragments, being the step with the highest activation energy, and thus affecting the whole catalysis. Our activation strain and quantitative molecular orbital (MO) analyses elucidate the mechanistic details and reveal why cobalt performs better than rhodium and iridium catalysts outlining general principles for rational design of catalysts to be used in these processes.

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Section: Introductionmentioning

confidence: 99%

Group 9 Metallacyclopentadienes as Key Intermediates in [2+2+2] Alkyne Cyclotrimerizations. Insight from Activation Strain Analyses

2018

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“… Mechanism for the [2+2+2] cycloaddition of acetylene to give benzene catalyzed by a half‐sandwich Rh I fragment in the hypothesis that an ancillary ligand (L=CO) remains bonded to the metal throughout the whole catalytic cycle …”

Section: Resultsmentioning

confidence: 99%

“…Given that our purpose was to compare different catalysts with identical mechanisms, the TOF ratio is a meaningful value. In fact, it benefits from a large error compensation and electronic energies can be used, as entropic contributions are likely very similar in analogous mechanisms …”

Section: Computational Detailsmentioning

confidence: 99%

Half‐Sandwich Metal‐Catalyzed Alkyne [2+2+2] Cycloadditions and the Slippage Span Model

2018

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Half‐sandwich RhI compounds display good catalytic activity toward alkyne [2+2+2] cycloadditions. A peculiar structural feature of these catalysts is the coordination of the metal to an aromatic moiety, typically a cyclopentadienyl anion, and, in particular, the possibility to change the bonding mode easily by the metal slipping over this aromatic moiety. Upon modifying the ancillary ligands, or proceeding along the catalytic cycle, hapticity changes can be observed; it varies from η5, if the five metal–carbon distances are identical, through η3+η2, in the presence of allylic distortion, and η3, in the case of allylic coordination, to η1, if a σ metal–carbon bond forms. In this study, we present the slippage span model, derived with the aim of establishing a relationship between slippage variation during the catalytic cycle, quantified in a novel and rigorous way, and the performance of catalysts in terms of turnover frequency, computed with the energy span model. By collecting and comparing new data and data from the literature, we find that the highest performance is associated with the smallest slippage variation along the cycle.

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“…Increased activity of indenylmetal catalysts has frequently been associated with the traditional explanation of the indenyl effect, i.e. a change in hapticity along the reaction coordinate, which is likely to be operative when substrate coordination to the metal center is a key step of the reaction mechanism . However, a more facile η 5 ‐to‐ η 3 rearrangement for Ind may not always be at the origin of increased catalytic activity.…”

Section: Introductionmentioning

confidence: 99%

Desulfurization of model and real fuels by extraction and oxidation processes using an indenylmolybdenum tricarbonyl pre‐catalyst

Julião

Gomes

Pillinger

et al. 2020

Applied Organom Chemis

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Regulations on the permissible levels of sulfur in transportation fuels are becoming ever more strict, with a global shift towards “zero sulfur” fuels, and the revamp of existing hydrodesulfurization (HDS) facilities to meet these lower caps is cost‐prohibitive. Metal‐catalyzed sulfoxidation chemistry is viewed as an economically viable desulfurization strategy that could complement conventional HDS technology. In the present work, the complex [η5‐IndMo(CO)3Me] (1) (Ind = indenyl) was employed in the catalytic oxidative desulfurization (CODS) of model and real liquid fuels, using aqueous hydrogen peroxide (H2O2) as oxidant. After optimization of the CODS reaction parameters (diesel/H2O2 ratio, catalyst amount, temperature), a high‐sulfur (2000 ppm) model diesel containing benzothiophene, dibenzothiophene, 4‐methyldibenzothiophene and 4,6‐dimethyldibenzothiophene could be completely desulfurized within 2 hr under solvent‐free conditions or in the presence of the ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM]PF6) as extraction solvent. The catalyst formed under solvent‐free conditions could be recycled without a significant decrease in desulfurization activity. The high performance of the CODS system was verified in the sulfur removal from a commercial untreated diesel fuel with a sulfur content of 2300 ppm, and a jet fuel with a sulfur content of 1100 ppm. Solvent‐free CODS in combination with initial/final extraction gave desulfurization efficiencies of 70% for the diesel fuel and 55% for the jet fuel. CODS with [BMIM]PF6 in combination with initial/final extraction led to a sulfur removal of 95.9% for the diesel fuel, which is one of the best results yet reported for ODS of commercial diesels.

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Indenyl Effect Due to Metal Slippage? Computational Exploration of Rhodium‐Catalyzed Acetylene [2+2+2] Cyclotrimerization

Cited by 35 publications

References 54 publications

Group 9 Metallacyclopentadienes as Key Intermediates in [2+2+2] Alkyne Cyclotrimerizations. Insight from Activation Strain Analyses

Group 9 Metallacyclopentadienes as Key Intermediates in [2+2+2] Alkyne Cyclotrimerizations. Insight from Activation Strain Analyses

Half‐Sandwich Metal‐Catalyzed Alkyne [2+2+2] Cycloadditions and the Slippage Span Model

Desulfurization of model and real fuels by extraction and oxidation processes using an indenylmolybdenum tricarbonyl pre‐catalyst

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