The activity of indenylidene derivatives in olefin metathesis catalysts

Voccia, Maria; Nolan, Steven P.; Cavallo, Luigi; Poater, Albert

doi:10.3762/bjoc.14.275

Cited by 8 publications

(6 citation statements)

References 71 publications

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“…On the other hand, there is the Py‐ p C=O[NHCH 2 (CF 2 ) 2 CF 3 ] , for which the NICS(0) and NICS(1) values show opposite results with respect the difference between mono and bimetallic structures. Taking into account that A is 2.2 kcal/mol more stable than B , the NICS(1) value seems more correct, since it predicts that A is more aromatic than B and A → B . Thus, the aromaticity study based on NICS(1) confirms the stabilizing contribution of the π‐stacking between axial ligands.…”

Section: Resultsmentioning

confidence: 99%

Axial Ligand Effects of Ru‐BDA Complexes in the O–O Bond Formation via the I2M Bimolecular Mechanism in Water Oxidation Catalysis

2019

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A detailed computational investigation of the mechanistic aspects of the water oxidation catalysis (WOC) for ruthenium‐based catalysts [Ru(bda)(isoq)2] (H2bda = 2,2′‐bipyridine‐6,6′‐dicarboxylic acid; isoq = isoquinoline). Density functional theory (DFT) calculations describe the kinetics by means of the energy barrier that leads to the O–O coupling, the rate‐limiting step for WOC. To test the effect of the axial ligand environment, we investigated bda complexes with para‐substituted isoquinolines, phthalazines and pyridines. Since previous screening analyses of the potential energy surface revealed a face to face orientation of metal‐oxo species to be best for facilitating the O–O bond formation, this paper probes the deeper role of the axial ligands that saturate the Ru(bda) based complexes from a computational point of view.

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Section: Resultsmentioning

confidence: 99%

Axial Ligand Effects of Ru‐BDA Complexes in the O–O Bond Formation via the I2M Bimolecular Mechanism in Water Oxidation Catalysis

2019

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“…This is a welcome opportunity to gauge the effect of the two different NHC ligands, IMes and SIMes, in 5a and 5b . The electronic and steric effects of these two ligands are still a matter of debate. − …”

Section: Resultsmentioning

confidence: 99%

Z-Selective Monothiolate Ruthenium Indenylidene Olefin Metathesis Catalysts

et al. 2020

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Ru-alkylidenes bearing sterically demanding arylthiolate ligands (SAr) constitute one of only two classes of catalyst that are Z-selective in metathesis of 1alkenes. Of particular interest are complexes bearing pyridine as a stabilizing donor ligand, [RuCl(SAr)(CHR)(NHC)(py)] (R = phenyl or 2-thienyl, NHC = N-heterocyclic carbene, py = pyridine), which initiate catalysis rapidly and give appreciable yields combined with moderate to high Z-selectivity within minutes at room temperature. Here, we extend this chemistry by synthesizing and testing the first two such complexes (5a and 5b) bearing 3-phenylindenylidene, a ligand known to promote stability in other ruthenium-based olefin metathesis catalysts. The steric pressure resulting from the three bulky ligands (the NHC, the arylthiolate, and the indenylidene) forces the thiolate ligand to position itself trans to the NHC ligand, a configuration different from that of the corresponding alkylidenes. Surprisingly, although this configuration is incompatible with Z-selectivity and slows down pyridine dissociation, the two new complexes initiate readily at room temperature. Although their thermal stability is lower than that of typical indenylidene-bearing catalysts, 5a and 5b are fairly stable in catalysis (TONs up to 2200) and offer up to ca. 80% of the Z-isomer in prototypical metathesis homocoupling reactions. Density functional theory (DFT) calculations confirm the energetic cost of dissociating pyridine from 5a (= M1-Py) to generate 14-electron complex M1. Whereas the latter isomer does not give a metathesis-potent allylbenzene π-complex, it may isomerize to M1-trans and M2, which both form π-complexes in which the olefin is correctly oriented for cycloaddition. The olefin orientation in these complexes is also indicative of Z-selectivity.

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“…In addition to the overall activity, this also implies chemo-, regio-and stereoselectivity of the metathesis event. [5] Yet, we have a very good picture of many mechanistic details, both from the experimental [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20] and theoretical [21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39] point of view. However, trying to correlate all these details into a single picture is complicated as the catalysts, the experimental conditions, or the computational approach, change from one work to the other, [40] apart from any decomposition that those olefin metatheses potentially suffer.…”

Section:  Introductionmentioning

confidence: 99%

Regio, stereo and chemoselectivity of 2nd generation Grubbs ruthenium-catalyzed olefin metathesis

et al. 2022

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The examination of cross metathesis reactions leading to the desired product has been conducted to uncover computationally the origin of the chemo-, regio-and stereoselectivity. The comparison between the relative stabilities of all involved intermediates and products, together with the transition states, links to the probability for the respective pathway. Particularly, the respective transition states for each reaction tune the regio-and stereoselectivity because they lead to define the energy barriers needed to be overcome to form the new olefin as final product. The broad range of studied reactions with the 2 nd generation Grubbs catalysts allows concluding in detail the points to pay attention and thus helps to understand the chemo-, regio-and stereoselectivity in new olefin metathesis reactions. Here, a web-server joins all these mechanistic insights which is intented to support future predictive olefin metathesis catalysis.

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The activity of indenylidene derivatives in olefin metathesis catalysts

Cited by 8 publications

References 71 publications

Axial Ligand Effects of Ru‐BDA Complexes in the O–O Bond Formation via the I2M Bimolecular Mechanism in Water Oxidation Catalysis

Axial Ligand Effects of Ru‐BDA Complexes in the O–O Bond Formation via the I2M Bimolecular Mechanism in Water Oxidation Catalysis

Z-Selective Monothiolate Ruthenium Indenylidene Olefin Metathesis Catalysts

Regio, stereo and chemoselectivity of 2nd generation Grubbs ruthenium-catalyzed olefin metathesis

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