Cationic molybdenum oxo alkylidenes stabilized by N-heterocyclic carbenes: from molecular systems to efficient supported metathesis catalysts

Musso, Janis V.; Silva, Jordan De Jesus; Benedikter, Mathis; Groos, Jonas; Frey, Wolfgang; Copéret, Christophe; Buchmeiser, Michael R.

doi:10.1039/d2sc03321f

Cited by 8 publications

(4 citation statements)

References 83 publications

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“…Direct comparisons of activity between 1@SZO and 1@SiO 2 are difficult due to the unexpected solvent effects for the former catalyst, but the olefin metathesis activity of 1@SZO suggests that other alkylidenes supported on SZO should also show activity in metathesis and/or direct conversion of ethylene to propylene. However, 1@SZO is undoubtedly far less active in olefin metathesis than cationic W or Mo alkylidenes supported on silica containing stabilizing N-heterocyclic carbene ligands . These particular studies suggest that addition of neutral ligands to 1@SZO coupled with modification of the donor ligands on W may result in catalysts with higher activities and stabilities.…”

Section: Discussionmentioning

confidence: 99%

“…It is not clear how modifying the support from silica, which as noted above behaves as an X- or LX-type ligand, to a weakly coordinating sulfated oxide would affect reactivity in olefin metathesis reactions. The charge at the Mo or W center is not an inherent limitation in catalyst design because cationic alkylidenes stabilized by N-heterocyclic carbene ligands are active in metathesis reactions in solution or when immobilized onto silica supports . This paper describes the reaction of SZO with W(O)(Adene)(2,5-dimethylpyrrolide) 2 ( 1 ; Adene = 2-adamantylidene) to form an active olefin metathesis catalyst (eq ).…”

Section: Introductionmentioning

confidence: 99%

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A Tungsten Oxo Alkylidene Supported on Sulfated Zirconium Oxide for Olefin Metathesis

et al. 2023

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The reaction of W(O)(Adene)(2,5-dimethylpyrrolide) 2 (1; Adene = 2-adamantylidene) and sulfated zirconium oxide (SZO) results in the formation of [W(O)(Adene)(2,5dimethylpyrrolide)][SZO] (1@SZO). 1@SZO reacts with 13 Clabeled ethylene to give 1-13 C-adamantylethylene and square pyramidal [W(O)(CH 2 ) 3 (2,5-dimethylpyrrolide)][SZO] (2) as major reaction products; small amounts of [ 13 C]propene and [W(O)(H 2 C�CH 2 )(2,5-dimethylpyrrolide)][SZO] (3) also form in this reaction. 1@SZO is active in olefin metathesis of terminal olefins, including methyl 10-undecenoate, to give the thermodynamic E-olefin product; and also catalyzes the direct formation of propylene from ethylene. Article pubs.acs.org/Organometallics

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Tungsten Oxo Alkylidene Supported on Sulfated Zirconium Oxide for Olefin Metathesis

et al. 2023

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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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“…Considering that NHC ligands are also σ-donor/π-acceptor ligands, they can be considered as isolobal . Therefore, we herein synthesized the surrogate complex derived from cationic Schrock alkylidenes, specifically of the class of Buchmeiser olefin metathesis catalysts, having a second NHC stabilizing ligand in the trans position. ,− This cationic TBP tungsten oxo-methylidene complex ( 1 ), along with neutral octahedral oxo-methylidene ( 2 ) and isostructural oxo-methylidyne ( 3 ) analogues, provides a 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. The comparison of complex 1 with oxo-methylidyne 3 , which features a distinct bonding environment due to additional π-bonding, and with oxo-methylidene 2 , having a distinct geometry, helps to build a detailed relationship between the electronic structure and NMR response.…”

Section: Introductionmentioning

confidence: 99%

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

Kakiuchi,

Docherty,

Berkson

et al. 2024

J. Am. Chem. Soc.

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Olefin metathesis has become an efficient tool in synthetic organic chemistry to build carbon−carbon bonds, thanks to the development of Grubbs-and Schrock-type catalysts. Olefin coordination, a key and often rate-determining elementary step for d 0 Schrock-type catalysts, has been rarely explored due to the lack of accessible relevant molecular analogues. Herein, we present a fully characterized surrogate of this key olefin-coordination intermediate, namely, a cationic d 0 tungsten oxo-methylidene complex bearing two N-heterocyclic carbene ligands�[WO(CH 2 )Cl(IMes) 2 ](OTf) (1) (IMes = 1,3-dimesitylimidazole-2-ylidene, OTf−triflate counteranion), resulting in a trigonal bipyramidal (TBP) geometry, along with its neutral octahedral analogue [WO(CH 2 )Cl 2 (IMes) 2 ] (2)�and an isostructural oxo-methylidyne derivative [WO(CH)Cl(IMes) 2 ] (3). The analysis of their solid-state 13 C and 183 W MAS NMR signatures, along with computed 17 O NMR parameters, helps to correlate their electronic structures with NMR patterns and evidences the importance of the competition among the three equatorial ligands in the TBP complexes. Anchored on experimentally obtained NMR parameters for 1, computational analysis of a series of olefin coordination intermediates highlights the interplay between σand π-donating ligands in modulating their stability and further paralleling their reactivity. 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 demanding.

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Cationic molybdenum oxo alkylidenes stabilized by N-heterocyclic carbenes: from molecular systems to efficient supported metathesis catalysts

Abstract: The first cationic molybdenum oxo complexes were synthesized and immobilized on partially dehydroxylated silica. Vastly enhanced catalytic activity for terminal olefins was found compared to their neutral congeners.

Cited by 8 publications

References 83 publications

A Tungsten Oxo Alkylidene Supported on Sulfated Zirconium Oxide for Olefin Metathesis

A Tungsten Oxo Alkylidene Supported on Sulfated Zirconium Oxide for Olefin Metathesis

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

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

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