Cationic Group VI Metal Imido Alkylidene <i>N</i>‐Heterocyclic Carbene Nitrile Complexes: Bench‐Stable, Functional‐Group‐Tolerant Olefin Metathesis Catalysts

Benedikter, Mathis; Musso, Janis V.; Frey, Wolfgang; Schowner, Roman; Buchmeiser, Michael R.

doi:10.1002/ange.202011666

Cited by 10 publications

(6 citation statements)

References 40 publications

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“…Unfortunately, the 1 J CH coupling constants of the alkylidene protons, which would allow for an unambiguous assignment of syn ‐ and anti ‐rotamers, could not be determined. However, based on literature data, [ 14,23 ] we tentatively assign the signals at δ = 9.85 and 9.83 ppm to the nitrile‐free syn ‐isomers and those at δ = 10.42, 10.39, and 10.31 ppm to the nitrile‐containing syn ‐isomers. In the olefinic region, several sets of pseudo‐triplets and doublets are observed at δ = 5.48 (d, 3 J = 11.4 Hz), 5.47 (d, 3 J = 12.2 Hz), 5.12 (t, 3 J = 11.4 Hz), 4.94 (t, 3 J = 11.4 Hz), 4.88 (t, 3 J = 11.3 Hz), 4.87 (t, 3 J = 11.2 Hz) and 4.81 (t, 3 J = 11.2 Hz), all assignable to cis ‐configured –( cyclo ‐C 5 H 8 )‐C H = C H ‐R double bonds in the short chain oligomers.…”

Section: Resultsmentioning

confidence: 82%

“…Indeed, this is different from what is observed at least for some cationic Mo imido alkylidene NHC complexes. [ 14 ] Notably, fast solvent dissociation has also been proposed by Schrock et al. for neutral Mo imido alkylidene complexes.…”

Section: Resultsmentioning

confidence: 89%

“…In many cases, cis‐ isotactic ( cis‐it ), trans‐ isotactic ( trans‐it ), cis‐ syndiotactic ( cis‐st ), or trans‐ syndiotactic (trans‐st ) structures are formed virtually selectively. [ 7,8 ] More recently, the new class of cationic molybdenum and tungsten alkylidene NHC catalysts bearing imido, oxo and sulfido ligands, [ 9–28 ] respectively, has been developed. Compared to Schrock‐type catalysts, this class of catalysts is characterized by a generally increased tolerance toward oxygen, moisture and functional groups [ 14,15,29 ] as well as by higher activities and productivities with turnover numbers exceeding 1.2 million when supported on silica.…”

Section: Introductionmentioning

confidence: 99%

“…[ 7,8 ] More recently, the new class of cationic molybdenum and tungsten alkylidene NHC catalysts bearing imido, oxo and sulfido ligands, [ 9–28 ] respectively, has been developed. Compared to Schrock‐type catalysts, this class of catalysts is characterized by a generally increased tolerance toward oxygen, moisture and functional groups [ 14,15,29 ] as well as by higher activities and productivities with turnover numbers exceeding 1.2 million when supported on silica. [ 30 ] So far, molybdenum and tungsten imido alkylidene N‐heterocyclic carbene (NHC) complexes have been shown to allow for the stereoselective ROMP of various norbornene‐ (NBE) based monomers, thereby allowing for the selective formation of either cis‐it , trans‐it , cis‐st , or trans‐st structures.…”

Section: Introductionmentioning

confidence: 99%

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Stereoselective Ring‐Opening Metathesis Polymerization with Tungsten Sulfido Alkylidene N‐Heterocyclic Carbene Complexes

Buchmeiser

Probst

Wang

et al. 2022

Macro Chemistry & Physics

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A series of cationic tungsten sulfido alkylidene N-heterocyclic carbene (NHC) complexes (W01 -W09) of the general formula [W(S)(CHCMe 3 )(X)(NHC) (CMe 3 CN) + B(Ar F ) 4 − ] (NHC = 1,3-dimesitylimidazol-2-ylidene, IMes; 1,3-dimesityl-4,5-dichloroimidazol-2-ylidene, IMesCl 2 ; 1,3-bis(2,6xdiisopropyl)phenyl)imidazol-2-ylidene, IDipp; X = Cl, C 6 F 5 O, 2,6-Ph 2 -C 6 H 3 ; B(Ar F ) 4 − = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) are used as initiators in the stereoselective ring-opening metathesis polymerization (ROMP) of (+) 2,3-endo, exo-dicarbomethoxynorborn-5-ene ((+)DCMNBE, M1). Trans-isospecifity up to 84% is achieved along with varying percentages of cis-syndiospecifity. The different extent of trans-isospecifity is compared to the one of related benchmark cationic molybdenum and tungsten imido and tungsten oxo alkylidene NHC complexes. Mechanistic investigations suggest that the syn-isomer of a nitrile-free initiator reacts with M1 presumably in an ene anti fashion to yield a syn-first insertion product via turnstile rearrangement, which accounts for the predominant trans-isospecifity of the polymerization. The cis-syndiotactic sequences are proposed to stem from the competing ene syn addition of M1 to a nitrile-containing syn-isomer of the initiator.

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Section: Resultsmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stereoselective Ring‐Opening Metathesis Polymerization with Tungsten Sulfido Alkylidene N‐Heterocyclic Carbene Complexes

Buchmeiser

Probst

Wang

et al. 2022

Macro Chemistry & Physics

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“…Employing an NHC as a σ-donor and -acceptor ligand, formally being isolobal to an olefin at a d 0 metal, we have been able to construct the desired surrogate complex derived from cationic Schrock alkylidenes, specifically of the class of Buchmeiser olefin metathesis catalysts, having a second NHC stabilizing ligand in trans position. [42][43][44][45][46][47][48][49][50][51] This cationic trigonal bipyramidal tungsten oxo-methylidene complex (1), along with neutral octahedral oxo-methylidene (2) and isostructural oxomethylidyne (3) analogs provide basis to assess the details of the first step of olefin metathesis catalysis, based on the analysis of 13 C and 183 W solid-state NMR spectra, augmented by computations. This study provides detailed picture for the olefin (de-)coordination step addressing its electronic structure and the role of ligand sets that are compensating the coordination sphere: alkylidene, E-type ligand, and a pair of strong and weak σ-donor ligands…”

Section: Introductionmentioning

confidence: 99%

Origin of Reactivity Trends of an Elusive Metathesis Intermediate from NMR Chemical Shift Analysis of Surrogate Analogs

Kakiuchi,

Docherty,

Berkson

et al. 2024

Preprint

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Olefin metathesis has been established as an efficient tool to build carbon-carbon bonds, and its widespread applications in organic synthesis have been made possible by the development of efficient homogeneous catalysts – Grubbs and Schrock-type – that operate through the same intermediates and Chauvin mechanism. With d0 Schrock-type catalysts, the first elementary step, olefin-coordination, is often rate determining, but it been rarely explored due to the lack of accessible relevant molecular analogs. Here, we develop a surrogate of this key olefin-coordination intermediate, namely a cationic d0 tungsten oxo-methylidene complex bearing two N-heterocyclic carbene ligands, [WO(CH2)Cl(IMes)2](OTf) (1) (IMes = 1,3-dimesitylimidazole-2-ylidene; OTf – triflate counter-anion) resulting in a trigonal bipyramidal (TBP) geometry, along with its neutral octahedral analog [WO(CH2)Cl2(IMes)2] (2), and an isostructural oxo-methylidyne derivative [WO(CH)Cl(IMes)2] (3). These compounds were fully characterized by state-of-the-art methods, including single-crystal X-ray diffraction (scXRD) and multinuclear (1H, 13C, 183W) solution NMR spectroscopy. The analysis of their solid-state 13C and 183W MAS NMR signatures, along with computed 17O NMR parameters, helps to correlate their electronic structures with NMR patterns and evidences the importance of the competition between the three equatorial ligands in the TBP complexes. Further analysis validates the suitability of complex 1 as a surrogate molecule to interrogate the electronic structure of the key olefin coordination intermediate of the Chauvin cycle. Anchored on experimentally obtained NMR parameters for 1, computational analysis of a series of olefin coordination intermediates highlights the interplay between σ- and π-donating ligands in modulating the stability of TBP olefin-coordination intermediates, paralleling their reactivity. In this work, NMR spectroscopy descriptors reveal the origin for the advantage of the dissymmetry in σ-donating abilities of ancillary ligands in Schrock-type catalysts: weak σ-donors avoid the orbital-competition with the oxo ligand upon formation of a TBP olefin-coordination intermediate, while stronger σ-donors compromise M≡O triple bonding and thus render olefin coordination step energy expensive.

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In Vivo Olefin Metathesis in Microalgae Upgrades Lipids to Building Blocks for Polymers and Chemicals

Schunck

Mecking

2022

Angewandte Chemie

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Sustainable sources are key to future chemicals production. Microalgae are promising resources as they fixate carbon dioxide to organic molecules by photosynthesis. Thereby they produce unsaturated fatty acids as established raw materials for the industrial production of chemical building blocks. Although these renewable feedstocks are generated inside cells, their catalytic upgrading to useful products requires in vitro transformations. A synthetic catalysis inside photoautotrophic cells has remained elusive. Here we show that a catalytic conversion of renewable substrates can be realized directly inside living microalgae. Organometallic catalysts remain active inside the cells, enabling in vivo catalytic olefin metathesis as new-to-nature transformation. Stored lipids are converted to long-chain dicarboxylates as valuable building blocks for polymers. This is a key step towards the long-term goal of producing desired renewable chemicals in microalgae as living "cellular factories".

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Cationic Group VI Metal Imido Alkylidene N‐Heterocyclic Carbene Nitrile Complexes: Bench‐Stable, Functional‐Group‐Tolerant Olefin Metathesis Catalysts

Cited by 10 publications

References 40 publications

Stereoselective Ring‐Opening Metathesis Polymerization with Tungsten Sulfido Alkylidene N‐Heterocyclic Carbene Complexes

Stereoselective Ring‐Opening Metathesis Polymerization with Tungsten Sulfido Alkylidene N‐Heterocyclic Carbene Complexes

Origin of Reactivity Trends of an Elusive Metathesis Intermediate from NMR Chemical Shift Analysis of Surrogate Analogs

In Vivo Olefin Metathesis in Microalgae Upgrades Lipids to Building Blocks for Polymers and Chemicals

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