?-Fluoroalkylamides, a new source of nonhydrated fluoride ion. 3.19F NMR spectra of perfluoro carbanions generated by means of N,N,N?,N?-tetramethylformamidinium bifluoride

Delyagina, N. I.; Igumnov, S. M.; Knunyants, I. L.

doi:10.1007/bf00963403

Cited by 6 publications

(3 citation statements)

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“…The perfluorinated carbanionic species HMG + [C(CF 3 ) 3 ] -, prepared from HMG + HF 2or HMG + Fand perfluoroisobutene, was found to be a stable solid. 22,23 The lipophilic and robust HMG + could be the cation of choice to get stable HMG + perfluoroalkoxides since the positive charge is distributed over three nitrogen atoms. Searching for a general route to pure hexaalkylguanidinium fluorides containing no HF 2as precursors for hexaalkylguanidinium perfluoroalkoxides avoiding SF 4 and its derivatives, we decided to study the reactions of bis(dialkylamino)methane derivatives with (dialkylamino)trimethylsilanes.…”

Section: Introductionmentioning

confidence: 99%

Hexaalkylguanidinium and 2-(Dialkylamino)-1,3-dimethylimidazolinium Trimethyldifluorosiliconates and Perfluoroalkoxides. Accidental Isolation and Molecular Structure of [C(NMe₂)₃]⁺F^-·6CH₂Cl₂

et al. 2002

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Hexaalkylguanidinium and 2-(dialkylamino)-1,3-dimethylimidazolinium trimethyldifluorosiliconates, precursors for two stable hexaalkylguanidinium perfluoroalkoxides, were synthesized by treating commercially available bis(dialkylamino)difluoromethane derivatives with (dialkylamino)trimethylsilanes in aprotic media. With hexamethylguanidinium pentafluoroethoxide the introduction of the lipophilic and electronegative C2F5O group was straightforwardly achieved in the case of primary and secondary alkyl triflates to furnish the respective fluorinated ethers. The molecular structures of [(CH2NMe)2C(NEt2)]+[Me3SiF2]- and [C(NMe2)3]+F-*6CH2Cl2 were determined, showing in the latter case a fluoride anion octahedrally coordinated by six methylene chloride molecules via hydrogen bridges with a F...H distance of 205 pm (C...F distance 270.0(3) pm).

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Section: Introductionmentioning

confidence: 99%

Hexaalkylguanidinium and 2-(Dialkylamino)-1,3-dimethylimidazolinium Trimethyldifluorosiliconates and Perfluoroalkoxides. Accidental Isolation and Molecular Structure of [C(NMe₂)₃]⁺F^-·6CH₂Cl₂

et al. 2002

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“…Reaction was conducted as above and the resulting lower layer was shown (g.1.c.) to be a single component and confirmed as perfluoro-4-ethyl-3,4dimethylhex-3-ene (6) by a comparison of 19F n.m.r. data with authentic material.…”

Section: Perfluoro-t-butylcaesiummentioning

confidence: 79%

“…The stereochemistry of carbanions is of considerable interest and, a priori we would expect planar systems which would All unmarked bonds to F (6) 8 I F minimise the quite considerable steric requirements of perfluoroalkyl groups. In this context, it is worth emphasising that, with such groups, covalent radii are themselves an insufficient indication of steric requirements because the systems are (10) abundant in non-bonding electron pairs and their associated repulsions.…”

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confidence: 99%

Reactions involving fluoride ion. Part 34. Stable perfluorinated carbanions

Bayliff¹,

Chambers²

1988

J. Chem. Soc., Perkin Trans. 1

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A remarkable series of perfluoroalkyl anions, generated by reaction of caesium fluoride with various perfluorinated alkenes have been observed by 19F and 13C n.m.r. spectroscopy. Trapping experiments are described and threshold temperatures are established for the onset of fluoride ion exchange. The effects of counter ions are compared and (Me,N),S+ (TAS) salts are more readily produced than Cs+ salts, but exchange of fluoride ion with fluorinated alkenes occurs more readily with TAS salts. Ph,P+ and Bu,N+ salts could not be obtained. Competition experiments for CsF between various perfluoroalkenes has established orders of carbanion stability.Carbanions take up a central role in the chemistry of unsaturated fluorocarbons ' in a way that is analogous to the role of carbocations in the chemistry of unsaturated hydrocarbons. Indeed, many of the papers in this series are concerned with pursuing a formal analogy between the chemistry of fluorinated carbanions, generated by reaction of fluoride-ion with unsaturated fluorocarbons, and the known chemistry involving proton-induced formation of carbocations. The spectacular work of Olah and co-~orkers,~ involving observable carbocations has, understandably, stimulated our search for observable fluorinated carbanions and we have previously described various perfluorinated cyclic anions and o-complexes. The (la) Scheme 1. generation of perfluoroalkyl anions k (1) + Oligomers(la), using fluoride ion sources in reactions of fluorinated alkenes (l), is well known3 but these are rarely long-lived since they promote oligomerisation reactions of the corresponding alkene (Scheme 1).Obviously, only in cases where K is large, or the rate constant for oligomerisation k is small, will there be a long-lived carbanion intermediate (la). Early attempts to observe perfluorinated tert-alkyl anions by n.m.r. were complicated by exchange phenomena involving proton transfers arising from hydrogen difluoride ions, used as the fluoride ion source.We now find that solutions of stable caesium salts of various simple perfluoroalkyl anions may be obtained and observed by n.m.r.; furthermore, some of these salts may even be obtained as solids. The most simple anion that we have observed, perfluorot-butylcaesium (Za), is obtained very simply by stirring a mixture containing perfluoroisobutene (2), caesium fluoride, and tetraglyme in a sealed system at room temperature. A clear homogeneous solution was obtained after removing excess of caesium fluoride and the n.m.r. spectra confirm, conclusively, formation of the salt (2a) (Figure 1). Quite clearly, the equilibrium lies completely on the side of the anion in solution and, from the sharpness of the spectra, exchange is slow on the n.m.r. timescale. On slight cooling ( 1 0 -1 5 "C) solid separated from solution, which was filtered and, on redissolving the solid, the solution spectrum of the anion (2a) was identical with that obtained previously (Figure I). Thus, the demonstration of a solid carbanion indicates the exciting possibility of growing crysta...

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Delocalized Lipophilic Cations as a Source of Naked Fluoride and Phase‐Transfer Catalysts

Kalinovich

Kazakova

Röschenthaler

2012

Efficient Preparations of Fluorine Compounds

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?-Fluoroalkylamides, a new source of nonhydrated fluoride ion. 3.19F NMR spectra of perfluoro carbanions generated by means of N,N,N?,N?-tetramethylformamidinium bifluoride

Cited by 6 publications

References 4 publications

Hexaalkylguanidinium and 2-(Dialkylamino)-1,3-dimethylimidazolinium Trimethyldifluorosiliconates and Perfluoroalkoxides. Accidental Isolation and Molecular Structure of [C(NMe₂)₃]⁺F^-·6CH₂Cl₂

Hexaalkylguanidinium and 2-(Dialkylamino)-1,3-dimethylimidazolinium Trimethyldifluorosiliconates and Perfluoroalkoxides. Accidental Isolation and Molecular Structure of [C(NMe₂)₃]⁺F^-·6CH₂Cl₂

Reactions involving fluoride ion. Part 34. Stable perfluorinated carbanions

Delocalized Lipophilic Cations as a Source of Naked Fluoride and Phase‐Transfer Catalysts

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?-Fluoroalkylamides, a new source of nonhydrated fluoride ion. 3.19F NMR spectra of perfluoro carbanions generated by means of N,N,N?,N?-tetramethylformamidinium bifluoride

Cited by 6 publications

References 4 publications

Hexaalkylguanidinium and 2-(Dialkylamino)-1,3-dimethylimidazolinium Trimethyldifluorosiliconates and Perfluoroalkoxides. Accidental Isolation and Molecular Structure of [C(NMe2)3]+F-·6CH2Cl2

Hexaalkylguanidinium and 2-(Dialkylamino)-1,3-dimethylimidazolinium Trimethyldifluorosiliconates and Perfluoroalkoxides. Accidental Isolation and Molecular Structure of [C(NMe2)3]+F-·6CH2Cl2

Reactions involving fluoride ion. Part 34. Stable perfluorinated carbanions

Delocalized Lipophilic Cations as a Source of Naked Fluoride and Phase‐Transfer Catalysts

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Hexaalkylguanidinium and 2-(Dialkylamino)-1,3-dimethylimidazolinium Trimethyldifluorosiliconates and Perfluoroalkoxides. Accidental Isolation and Molecular Structure of [C(NMe₂)₃]⁺F^-·6CH₂Cl₂

Hexaalkylguanidinium and 2-(Dialkylamino)-1,3-dimethylimidazolinium Trimethyldifluorosiliconates and Perfluoroalkoxides. Accidental Isolation and Molecular Structure of [C(NMe₂)₃]⁺F^-·6CH₂Cl₂