Transformation of Tetrafluoroethylene Using Transition-Metal Complexes

Doi, Ryohei; Zhou, Yong‐Gui; Ogoshi, Sensuke

doi:10.1055/a-1983-5059

Cited by 7 publications

(10 citation statements)

References 65 publications

(85 reference statements)

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“…Moreover, for small-bite-angle ligands that are restricted from opening the L–Ni–L angle, donor solvent effects may exert an inhibiting effect on additional TFE coordination. These observations contribute to a rare example of mechanistic studies of perfluorometallacycles and could help to develop new and more efficient catalytic systems. ,, …”

Section: Discussionmentioning

confidence: 91%

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Mechanism of Perfluoro-Nickelacyclopentane Formation from Tetrafluoroethylene: Effects of Ancillary Ligand Bite Angle

L. T. N. Porto,

Ghaffari,

Ovens

et al. 2023

Organometallics

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Metallacyclopentanes are important reaction intermediates for catalytic processes, such as selective ethylene oligomerization and diene cyclooligomerization. Reactions of fluoroalkenes with low-valent first row transition metal complexes tend to form stable fluorometallacyclopentane products. DFT studies conducted herein indicate that conversion of three-coordinate Ni(η 2 -C 2 F 4 )L 2 complexes (L 2 = 2 monodentate or one bidentate chelate) to perfluorometallacycle products Ni[κ 2 -(CF 2 ) 4 -]L 2 occurs preferentially via a four-coordinate intermediate Ni(η 2 -C 2 F 4 ) 2 L 2 ; an alternative three-coordinate pathway via Ni(η 2 -C 2 F 4 ) 2 L occurs only when L is extremely bulky. The transition structure for cyclization requires a dramatic increase in the L−Ni−L angle, which is perpendicular to the C−C bond-forming plane and initially affords a kinetic metallacycle intermediate resembling a trigonal bipyramidal geometry with one equatorial vacant site. The donor solvent, or intramolecular O-donor association with this intermediate, provides a low-energy pathway to the formation of the more stable square-planar metallacycle product. For bidentate chelate ligands, differential bite angles affect both coordination of a second C 2 F 4 ligand and the cyclization step. For small-bite-angle chelates, the cyclization transition state energies are higher relative to monodentate analogues. An experimental investigation of wide bite-angle bis(phosphine) ligands such as DPEphos and Bisbi showed the formation of additional nickelacyclopentane products with the coordination of a single P center to each Ni [DPEphos = bis(2-diphenylphosphino-phenyl) ether; Bisbi = 2,2′bis(diphenylphosphino-methyl)-1,1′-biphenyl].

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Section: Discussionmentioning

confidence: 91%

“…These observations contribute to a rare example of mechanistic studies of perfluorometallacycles and could help to develop new and more efficient catalytic systems. 20,39,47 ■ EXPERIMENTAL SECTION General Procedures. Experiments were conducted under nitrogen using Schlenk techniques or an MBRAUN glovebox.…”

Section: ■ Conclusionmentioning

confidence: 99%

Mechanism of Perfluoro-Nickelacyclopentane Formation from Tetrafluoroethylene: Effects of Ancillary Ligand Bite Angle

L. T. N. Porto,

Ghaffari,

Ovens

et al. 2023

Organometallics

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“…Development of the fourth generation of fluorinated gases, hydrofluoroolefins (HFOs), in air-conditioning and refrigeration came with the necessity of decreasing their global-warming potential . One effective way to synthesize HFOs is by transition metal catalysis, and environmental concerns with traditional methods employing HF and heavy metals have stimulated development of this area . Organonickel chemistry has played an important role in this field, allowing for the functionalization of easily accessed fluorometallacycles. − …”

Section: Introductionmentioning

confidence: 99%

Synthesis and Reactivity of Functionalized Fluoro-Nickelacyclopentanes

Mangin,

Porto,

Ovens

et al. 2024

Organometallics

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Fluoro-nickelacyclopentanes are key intermediates in the synthesis of hydrofluoro-carbons and fluorinated ketones. To better understand substituent effects on their reactivity, we have prepared a series of nickel complexes from perfluoro(methyl vinyl ether) (PMVE) and chloro-trifluoroethylene (CTFE). Both fluoroalkenes react with Ni(cod)2 + 2 equiv of P(O i Pr)3 to give regioselective formation of the tail-to-tail nickelacyclopentanes Ni[–CFX(CF2)2CFX–][P(O i Pr)3]2 (X = OCF3, Cl) as a 3:1 mixture of the trans/cis diastereomers for PMVE and the trans diastereomer selectively for CTFE. Reaction of both metallacycles with 1,2-bis(diphenylphosphino)ethane (dppe) displaces the phosphite ligands, affording two (X = OCF3) or one (X = Cl) diastereomer of electron-rich congeners Ni[–CFX(CF2)2CFX–](dppe). Although these dppe-derived metallacycles did not react cleanly with fluoride-abstracting Lewis acids (Et2O·BF3 or Me3SiOTf), heating trans-Ni[–CFCl(CF2)2CFCl–](dppe) induced the intramolecular nucleophilic attack by one –PPh2 arm of the dppe ligand on a C–Cl bond, affording both trans and cis diastereomers in a 1:1 ratio. Using the wider bite-angle bis(phosphine) xantphos with PMVE also gave the trans/cis nickelacyclopentanes, which feature κ3-P,O,P-xantphos coordination. With CTFE, the xantphos ligand gave an unexpected fluoro-nickelacyclopentane derivative proposed to result from tail-to-tail oxidative cyclization, followed by PPh2 + migration, leading to an unusual coupling of the fluoroalkyl moiety with the xanthene backbone.

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“…The conventional uses for tetrafluoroethylene (TFE) have been mostly limited to the production of tetrafluoroethylene-based polymers and copolymers with other alkenes; therefore, we have devoted significant effort to broadening the scope of TFE as a synthetic reagent . During the course of our research on the transformations of TFE, we discovered that its C–F bond can be cleaved efficiently using Lewis acidic coadditives, such as lithium iodide .…”

Section: Introductionmentioning

confidence: 99%

N-Heterocyclic Carbenes with Polyfluorinated Groups at the 4- and 5-Positions from [3 + 2] Cycloadditions between Formamidinates and cis-1,2-Difluoroalkene Derivatives

Ohashi,

Ando,

Murakami

et al. 2023

J. Am. Chem. Soc.

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We herein report the formation of fluorinated N-heterocyclic carbenes (NHCFs) that bear fluorine atoms at the 4- and 5-positions of the imidazol-2-ylidene ring. Treatment of sodium N,N′-bis(aryl)formamidinates with tetrafluoroethylene followed by the addition of LiBF4 induced a [3 + 2] cycloaddition to afford 4,5-difluorinated imidazolium salts, which served as the precursors for 4,5-difluorinated NHCs. A key feature of this procedure is its applicability to other perfluorinated compounds, which enabled us to incorporate polyfluorinated functional groups at 4- and 5-positions on the imidazol-2-ylidene skeleton. Thus, employing octafluorocyclopentene and hexafluorobenzene led to the formation of 4,4,5,5,6,6-hexafluoro-1,3-diaryl-3,4,5,6-tetrahydrocyclopenta[d]imidazolium (CypIPrF·HBF4) and 4,5,6,7-tetrafluoro-1,3-diarylbenzimidazolium (BIPrF·HBF4) salts, respectively. A thorough NMR analysis of these NHCFs, their selenium adducts, and their tricarbonyl nickel complexes, (NHCF)Ni(CO)3, demonstrated that the fluorine substituents, contrary to expectations, tend to act as electron donors owing to the considerable positive mesomeric effect, while the perfluorocyclopentene-fused and tetrafluorobenzo-fused rings are pure electron acceptors due to their strong negative inductive effect. The unique and increased π-accepting character of the perfluorocyclopentene-fused and tetrafluorobenzo-fused NHCFs in both stoichiometric and catalytic reactions is further demonstrated by employing (NHCF)Ni(CO)3 and (NHCF)AuCl species, respectively. Moreover, an analysis of the % buried volume (%V bur) values clearly suggests that the modification of the NHC backbone with polyfluorinated groups can drastically alter the electronic properties of the NHC ligand without substantially changing its steric properties. Our experimental results were further corroborated by a series of computational calculations.

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Transformation of Tetrafluoroethylene Using Transition-Metal Complexes

Cited by 7 publications

References 65 publications

Mechanism of Perfluoro-Nickelacyclopentane Formation from Tetrafluoroethylene: Effects of Ancillary Ligand Bite Angle

Mechanism of Perfluoro-Nickelacyclopentane Formation from Tetrafluoroethylene: Effects of Ancillary Ligand Bite Angle

Synthesis and Reactivity of Functionalized Fluoro-Nickelacyclopentanes

N-Heterocyclic Carbenes with Polyfluorinated Groups at the 4- and 5-Positions from [3 + 2] Cycloadditions between Formamidinates and cis-1,2-Difluoroalkene Derivatives

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