Cationic tungsten imido alkylidene N-heterocyclic carbene complexes for stereospecific ring-opening metathesis polymerization of norbornene derivatives

Musso, Janis V.; Benedikter, Mathis; Gebel, Paul; Gramm, Vincent; Wang, Dongren; Schowner, Roman; Buchmeiser, Michael R.

doi:10.1039/d1py01158h

Cited by 8 publications

(21 citation statements)

References 37 publications

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“…Complexes W01 – W03 bearing a chloro‐ligand show a trans ‐isospecifity between 66 and 84%, which is comparable to the trans ‐isospecifity found in the related W imido alkylidene NHC complexes [W(N‐2‐ t Bu‐C 6 H 4 )(CHCMe 2 Ph)Cl(IMes)(CMe 3 CN) + B(Ar F ) 4 − ] (81%) [ 11 ] or [W(N‐2,6‐Cl 2 ‐C 6 H 3 )(CHCMe 2 Ph)Cl(IMes)(CMe 3 CN) + B(Ar F ) 4 − ] (77%). [ 11 ]…”

Section: Resultsmentioning

confidence: 57%

“…The proposed reaction sequence that accounts for the formation of trans-it structures is outlined in Scheme 1 (top). [7,8,11,32,35] It is based on the finding that we could not observe any signals for the anti-isomers in the starting complexes W01 -W10, which is, however, no proof for their non-existence. In the formation of trans-it polymers, a monomer adds ene anti , i.e., with the C7-carbon of the NBE down, to a syn-isomer of the initiator.…”

Section: Stereoselective Romp: Mo-imido Versus W-imido/oxo/sulfide Al...mentioning

confidence: 81%

“…[11] Complexes W04 -W06 bearing the pentafluorophenoxide ligand allowed for a trans-isospecifity between 16 and 71%, which is, except for W05, again comparable to the trans-isospecifity observed with related cationic tungsten imido alkylidene NHC complexes [W(N-2,6-iPr 2 -C 6 H 3 )(CHCMe 2 Ph)(OC 6 F 5 )(IMes) (CMe 3 CN) + B(Ar F ) 4 − ] (88%), [31] [W(N-2,6-Me 2 -C 6 H 3 ) (CHCMe 2 Ph)(OC 6 F 5 )(IMes)(CMe 3 CN) + B(Ar F ) 4 − ] (52%), [11] [W(N-2,6-Cl 2 -C 6 H 3 )(CHCMe 2 Ph)(OC 6 F 5 )(IMes)(CMe 3 CN) + B(Ar F ) 4 − ] (56%), [11] and [W(N-2-CF 3 -C 6 H 3 )(CHCMe 2 Ph)(OC 6 F 5 ) (IMes)(CMe 3 CN) + B(Ar F ) 4 − ] (63%). [11] The same accounts for the cationic tungsten oxo alkylidene NHC complex W10, [12] which shows 70% trans-isospecifity. Complexes W07 -W09 bearing the 2,6-Ph 2 -C 6 H 3 -ligand allowed for similar trans-isospecifities between 57 and 73%.…”

Section: Resultsmentioning

confidence: 99%

“…Initiators W01 -W10 as well as monomer M1 were prepared according to the literature. [11,12,31] 1 H and 13 C NMR spectra were recorded using a Bruker Avance III 400 spectrometer at 400 and 100 MHz, respectively. COSY spectra were recorded on a Bruker Ascent 700 MHz spectrometer.…”

Section: Methodsmentioning

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: 57%

Section: Stereoselective Romp: Mo-imido Versus W-imido/oxo/sulfide Al...mentioning

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

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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“…Deuterated solvents were purchased from Eurisotop and dried by storage over 4 Å molecular sieves. The following compounds were prepared according to literature procedures: IMesCl 2 , [18] IMesMe 2 , [19] Na(BAr F ) 4 , [20] 2 a, [1g] 3, [1g] 4 a, [1g] 4 b, [1g] 5 a, [1g] 5 b-MeCN, [1g] 5 b, [1g] 5 c-MeCN, [1g] 5 c, [1g] 12, [2] 7 d, [21] 7 b, [22] 7 c, [23] 8 b [24] and 10 b. [24] All NMR spectra were recorded on a Bruker Avance III 400.…”

Section: Methodsmentioning

confidence: 99%

Predicting Catalytic Activity from ¹³C_CH Alkylidene Chemical Shift in Cationic Tungsten Oxo Alkylidene N‐Heterocyclic Carbene Complexes

et al. 2021

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A series of cationic tungsten oxo alkylidene N-heterocyclic carbene (NHC) complexes was synthesized and structurally characterized by single crystal X-ray diffraction. The 13 C NMR chemical shifts of the alkylidene C atoms of these complexes were correlated with the diamagnetic, paramagnetic and spinorbit chemical shifts calculated by DFT. A good correlation (R 2 = 0.90) between the DFT isotropic chemical shifts and the experimental chemical shift as well as a strong correlation between the DFT isotropic chemical shifts and the TOF 1min for the RCM of 1,7-octadiene was found. Further, a comparison of the catalyst geometries allowed for assigning tetracoordinate pseudotetrahedral catalysts to the most deshielded alkylidenes and to the highest TOF 1min , pentacoordinate square-planar catalysts to the intermediate deshielded alkylidenes and intermediate TOF 1min , and hexacoordinate and octahedral catalyst to the most shielded alkylidene and lowest TOF 1min . Analysis of the magnetic shielding tensors allowed for ascribing variations in the chemical shifts to electronic transitions between occupied molecular orbitals corresponding to the alkylidene-C and alkylidene-H σ-bonds and the empty molecular orbital corresponding to the W-alkylidene σ*-bond.

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Macrocyclization of Dienes under Confinement with Cationic Tungsten Imido/Oxo Alkylidene N‐Heterocyclic Carbene Complexes

Ziegler,

Bruckner,

Nowakowski

et al. 2023

ChemCatChem

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Macrocyclization reactions are still challenging due to competing oligomerization, which requires the use of small substrate concentrations. Here, the cationic tungsten imido and tungsten oxo alkylidene N‐heterocyclic carbene complexes [[W(N‐2,6‐Cl2‐C6H3)(CHCMe2Ph(OC6F5)(pivalonitrile)(IMes)+ B(ArF)4‐] (W1) and [W(O)(CHCMe2Ph(OCMe(CF3)2)(IMes)(CH3CN)+ B(ArF)4‐] (W2) (IMes = 1,3‐dimesitylimidazol‐2‐ylidene; B(ArF)4‐ = tetrakis(3,5‐bis(trifluoromethyl)phenyl borate) have been immobilized inside the pores of ordered mesoporous silica (OMS) with pore diameters of 3.3 and 6.8 nm, respectively, using a pore‐selective immobilization protocol. X‐ray absorption spectroscopy of W1@OMS showed that even though the catalyst structure is contracted due to confinement by the mesopores, both the oxidation state and structure of the catalyst stayed intact upon immobilization. Catalytic testing with four differently sized a,w‐dienes revealed a dramatically increased macrocyclization (MC) and Z‐selectivity of the supported catalysts compared to the homogenous progenitors, allowing high substrate concentrations of 25 mM. With the supported complexes, a maximum increase in MC‐selectivity from 27 to 81 % and in Z‐selectivity from 17 to 34 % was achieved. In general, smaller mesopores exhibited a stronger confinement effect. A comparison of the two supported tungsten‐based catalysts showed that W1@OMS possesses a higher MC‐selectivity, while W2@OMS exhibits a higher Z‐selectivity which can be rationalized by the structures of the catalysts.

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Cationic tungsten imido alkylidene N-heterocyclic carbene complexes for stereospecific ring-opening metathesis polymerization of norbornene derivatives

Cited by 8 publications

References 37 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

Predicting Catalytic Activity from ¹³C_CH Alkylidene Chemical Shift in Cationic Tungsten Oxo Alkylidene N‐Heterocyclic Carbene Complexes

Macrocyclization of Dienes under Confinement with Cationic Tungsten Imido/Oxo Alkylidene N‐Heterocyclic Carbene Complexes

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Cationic tungsten imido alkylidene N-heterocyclic carbene complexes for stereospecific ring-opening metathesis polymerization of norbornene derivatives

Cited by 8 publications

References 37 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

Predicting Catalytic Activity from 13CCH Alkylidene Chemical Shift in Cationic Tungsten Oxo Alkylidene N‐Heterocyclic Carbene Complexes

Macrocyclization of Dienes under Confinement with Cationic Tungsten Imido/Oxo Alkylidene N‐Heterocyclic Carbene Complexes

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Predicting Catalytic Activity from ¹³C_CH Alkylidene Chemical Shift in Cationic Tungsten Oxo Alkylidene N‐Heterocyclic Carbene Complexes