Latent ruthenium–indenylidene catalysts bearing a <i>N</i>-heterocyclic carbene and a bidentate picolinate ligand

Schmid, Thibault E.; Modicom, Florian; Dumas, Adrien; Borré, Etienne; Toupet, Loı̈c; Baslé, Olivier; Mauduit, Marc

doi:10.3762/bjoc.11.169

Cited by 10 publications

(5 citation statements)

References 27 publications

(21 reference statements)

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“…Since then, a number of additional light-activated systems have been developed, including catalysts with inherent photoswitchable characteristics that do not require the addition of a complementary photoactive compound. − Quite recently, Theunissen et al demonstrated exquisite temporal and spatial control over a suite of metathetic transformations using bis( N -heterocyclic carbene) (bis-NHC) complexes in combination with an oxidizing photocatalyst that induces dissociation of a NHC ligand . A variety of acid-activated catalysts, similar to the acetylacetonate-protected alkylidenes mentioned above, have also been established, such as amidobenzylidene , and aryloxybenzylidene chelates, − among a variety of other Ru chelates. ,− Similarly, thermally activated catalysts are becoming increasingly widespread. Such catalysts exhibit negligible initiation of a given substrate at room temperature.…”

Section: Introductionmentioning

confidence: 99%

Depolymerization of Cross-Linked Polybutadiene Networks in Situ Using Latent Alkene Metathesis

Herman

Seazzu

Hughes

et al. 2019

ACS Appl. Polym. Mater.

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We report a novel approach whereby cross-linked polybutadiene (PB) networks can be depolymerized in situ based on thermally activated alkene metathesis. A commercially available latent Ru catalyst, HeatMet, was compared to the common second-generation Hoveyda–Grubbs catalyst, HG2, in the metathetic depolymerization of PB. HeatMet was found to possess exceptional stability and negligible activity toward PB under ambient conditions, in solution and in bulk. This enabled cross-linked networks to be prepared containing homogeneously distributed Ru catalyst. The dynamic mechanical properties of networks containing HeatMet and cross-linked using alcohol–isocyanate or thiol–ene chemistry were evaluated during cross-linking and post-cross-linking under isothermal and nonisothermal heating. In both cases, above minimum catalyst loadings ranging from 0.004 to 0.024 mol %, the networks exhibited rapid degelation into a soluble oil upon heating to 100 °C. At these temperatures, extensive depolymerization of the PB segments through ring-closing metathesis of 1,4/1,2 diads by the activated HeatMet introduced network defects in significantly greater proportion than the original number of cross-links. The in situ depolymerization of cross-linked PB networks through latent catalysis, as described here, may enable facile disposal and recycling of PB encapsulants and adhesives, among other applications.

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Section: Introductionmentioning

confidence: 99%

Depolymerization of Cross-Linked Polybutadiene Networks in Situ Using Latent Alkene Metathesis

Herman

Seazzu

Hughes

et al. 2019

ACS Appl. Polym. Mater.

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“…The synthesis involved the reaction of N-heterocyclic carbene bearing precursor complexes M31 , HovII or M32 with excess of 5,7-dichloro-8-hydroxyquinoline or 5,7-dibromo-8-hydroxyquinoline in the presence of excess Cs 2 CO 3 as the base (see Scheme 1 ). The silver-free method [ 41 ] resulted in any case in the formation of at least two new products (as evidenced by thin-layer chromatography) which were separated by means of column chromatography. All obtained complexes are very stable in the solid state and can be stored for several days in solution in the presence of oxygen without any sign of decomposition.…”

Section: Resultsmentioning

confidence: 99%

Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

Wappel¹,

Fischer²,

Cavallo³

et al. 2016

Beilstein J. Org. Chem.

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SummaryA straightforward synthesis utilizing the ring-opening metathesis polymerization (ROMP) reaction is described for acid-triggered N,O-chelating ruthenium-based pre-catalysts bearing one or two 8-quinolinolate ligands. The innovative pre-catalysts were tested regarding their behavior in ROMP and especially for their use in the synthesis of poly(dicyclopentadiene) (pDCPD). Bearing either the common phosphine leaving ligand in the first and second Grubbs olefin metathesis catalysts, or the Ru–O bond cleavage for the next Hoveyda-type catalysts, this work is a step forward towards the control of polymer functionalization and living or switchable polymerizations.

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“…In type II systems, a donor ligand is tethered to one of the anionic ligands. In this case the chelation decelerates both initiation and propagation, and therefore, this layout is optimally used in acid-switchable systems . In the case of type III systems, a chelating carbene ligand is used.…”

Section: Strategies In the Design Of Latent Catalystsmentioning

confidence: 99%

Light-Activated Olefin Metathesis: Catalyst Development, Synthesis, and Applications

et al. 2020

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Conspectus The most important means for tuning and improving a catalyst’s properties is the delicate exchange of the ligand shell around the central metal atom. Perhaps for no other organometallic-catalyzed reaction is this statement more valid than for ruthenium-based olefin metathesis. Indeed, even the simple exchange of an oxygen atom for a sulfur atom in a chelated ruthenium benzylidene about a decade ago resulted in the development of extremely stable, photoactive catalysts. This Account presents our perspective on the development of dormant olefin metathesis catalysts that can be activated by external stimuli and, more specifically, the use of light as an attractive inducing agent. The insight gained from a deeper understanding of the properties of cis -dichlororuthenium benzylidenes opened the doorway for the systematic development of new and efficient light-activated olefin metathesis catalysts and catalytic chromatic-orthogonal synthetic schemes. Following this, ways to disrupt the ligand-to-metal bond to accelerate the isomerization process that produced the active precatalyst were actively pursued. Thus, we summarize herein the original thermal activation experiments and how they brought about the discoveries of photoactivation in the sulfur-chelated benzylidene family of catalysts. The specific wavelengths of light that were used to dissociate the sulfur–ruthenium bond allowed us to develop noncommutative catalytic chromatic-orthogonal processes and to combine other photochemical reactions with photoinduced olefin metathesis, including using external light-absorbing molecules as “sunscreens” to achieve novel selectivities. Alteration of the ligand sphere, including modifications of the N-heterocyclic carbene (NHC) ligand and the introduction of cyclic alkyl amino carbene (CAAC) ligands, produced more efficient light-induced activity and special chemical selectivity. The use of electron-rich sulfoxides and, more prominently, phosphites as the agents that induce latency widened the spectrum of light-induced olefin metathesis reactions even further by expanding the colors of light that may now be used to activate the catalysts, which can be used in applications such as stereolithography and 3D printing of tough metathesis-derived polymers.

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Latent ruthenium–indenylidene catalysts bearing a N-heterocyclic carbene and a bidentate picolinate ligand

Cited by 10 publications

References 27 publications

Depolymerization of Cross-Linked Polybutadiene Networks in Situ Using Latent Alkene Metathesis

Depolymerization of Cross-Linked Polybutadiene Networks in Situ Using Latent Alkene Metathesis

Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

Light-Activated Olefin Metathesis: Catalyst Development, Synthesis, and Applications

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