C6F5XeF, a versatile starting material in xenon–carbon chemistry

doi:10.1016/j.jfluchem.2004.01.019

Journal of Fluorine Chemistry

Volume 125, Issue 6, June 2004, Pages 981-988

https://doi.org/10.1016/j.jfluchem.2004.01.019 Get rights and content

Abstract

The molecules Ar_FXeF (Ar_F=C₆F₅, 2,4,6-C₆H₂F₃) with a more polar Xe–F bond than XeF₂ are versatile starting materials for substitution reactions. Fluorine-aryl substitutions with Cd(Ar_F)₂, C₆F₅SiMe₃/[F]⁻, and C₆F₅SiF₃ formed symmetric and/or asymmetric diarylxenon compounds. Applying C₆F₅BF₂, with a higher F⁻-affinity than the corresponding aryltrifluorosilane, in contrast gave the salt [RXe] [Ar_FBF₃]. Using the alkenyl and alkyl compounds CF₂=CFSiMe₃/[F]⁻, CF₃SiMe₃/[F]⁻, and Cd(CF₃)₂ in reactions with C₆F₅XeF, the perfluoroalkenyl or -alkyl transfer reagents were consumed without observing C₆F₅XeCF=CF₂ or C₆F₅XeCF₃ but the formation of Xe(C₆F₅)₂ (dismutation product) and in the latter case C₆F₅CF₃ (coupling product), gave hints of the desired intermediates.

Routes to diorgano xenon coumpounds starting from ArXeF.

Introduction

The first examples of xenon(II)–carbon compounds, salts containing the [C₆F₅Xe]⁺ cation, were prepared independently by Naumann [1] and Frohn [2] in 1989 and were structurally characterised by X-ray crystallography [3]. The development of the following decade which included alkynyl-, cycloalkenyl-, and alkenyl- in addition to arylxenon(II) compounds was summarised in two reviews [4]. Additionally, one example of a xenon(IV)–carbon compound is known: [C₆F₅XeF₂] [BF₄] [5].

Principally, three potential classes of xenon(II)–carbon compounds can be discussed: (a) salts with a xenonium cation [OrgXe]⁺ Y⁻, (b) neutral molecules with one or two xenon–carbon bonds OrgXe–Y or Org₂Xe, and (c) salts with a xenon–carbon fragment in the anions M [OrgXeY₂] or M [Org₂XeY]. The latter class has been unknown until now as well as the inorganic prototype M [XeF₃].

This paper contributes to class b. In addition to the symmetric molecules (Ar_F)₂Xe the asymmetric ones Ar_FXe(Ar_F)′ and Ar_FXeY are subjects of this paper. C₆F₅XeF (1) as starting material for both aims can be obtained by two different procedures: the F⁻-catalysed transfer of the aryl group C₆F₅ from C₆F₅SiMe₃ to XeF₂ [6] or the addition of the “naked” fluoride ion to the [C₆F₅Xe]⁺ cation in the corresponding [AsF₆]⁻ salt [7]. The first procedure always delivers an admixture of Xe(C₆F₅)₂.

In our previous work, we have shown the introduction of a second organo group into 1 [7]. With Cd(C₆F₅)₂ in CH₂Cl₂ we obtained the symmetric molecule Xe(C₆F₅)₂ (2) (Eq. (1)). $2 C_{6} F_{5} XeF + Cd (C_{6} F_{5})_{2} 1 → Xe (C_{6} F_{5})_{2} + CdF_{2} 2 ↓$

Me₃SiCN and its isotopomers Me₃Si $^{13} C$ N and Me₃SiC $^{15} N$ reacted spontaneously with 1 forming the asymmetric molecules C₆F₅XeCN (3a), C₆F₅Xe $^{13} C$ N (3b), and C₆F₅XeC $^{15} N$ (3c), respectively (Eq. (2)). $C_{6} F_{5} XeF 1 + Me_{3} SiCN → C_{6} F_{5} XeCN 3 a + Me_{3} SiF$

Different to the reaction described in Eq. (2), no reaction took place between 1 and the silylated nucleophile (Nu) Me₃SiC₆F₅.

In this paper, we will elucidate the usefulness of cadmium organyls and silyl compounds for the substitution of xenon-bonded fluorine in 1 by suitable nucleophiles. We will discuss the driving forces for the synthesis of new C₆F₅XeNu compounds as well as the influence of the Lewis acidity of the transfer reagents.

Section snippets

The substitution of fluorine in 1 by aryl groups

Analogously to (Eq. (1)), 1 reacted with the less fluorinated diarylcadmium Cd(2,4,6-C₆H₂F₃)₂ and formed the desired asymmetric diarylxenon compound 2,4,6-C₆H₂F₃XeC₆F₅ (4) but in addition the symmetric compounds Xe(C₆F₅)₂ (2) and Xe(2,4,6-C₆H₂F₃)₂ (5) were obtained. $22 C_{6} F_{5} XeF 1 + Cd (2,4,6- C_{6} H_{2} F_{3})_{2} → 22,4,6- C_{6} H_{2} F_{3} XeC_{6} F_{5} 4 (main product)+ CdF_{2} ↓+ Xe (C_{6} F_{5})_{2} 2 + Xe (2,4,6- C_{6} H_{2} F_{3})_{2} 5$

This dismutation is a new phenomenon in xenon–carbon chemistry. We have performed some control experiments to check the migration of

Conclusion

The high polarity of the Xe–F bond in ArXeF offers this class of molecules for introducing new organic groups into the C–Xe moiety. They are also potential and promising starting materials for proving the possiblities of new Xe–E bond combinations. Further work is in progress.

Experimental

The $^{1} H$ , $^{13} C$ , $^{19} F$ , and $^{129} Xe$ NMR spectra were recorded on Bruker spectrometers WP 80 SY ( $^{1} H$ at 80.13 MHz and $^{19} F$ at 75.39 MHz), AVANCE 300 ( $^{1} H$ at 300.13 MHz, $^{13} C$ at 75.47 MHz, $^{19} F$ at 282.40 MHz, and $^{129} Xe$ at 83.02 MHz), and DRX 500 ( $^{13} C$ at 125.76 MHz, $^{19} F$ at 470.59 MHz, and $^{129} Xe$ at 138.34 MHz). The chemical shifts are referenced to TMS ( $^{1} H$ , $^{13} C$ ), CCl₃F ( $^{19} F$ , with C₆F₆ as secondary reference (−162.9 ppm)), and XeOF₄ $^{129} Xe$ , with XeF₂ in MeCN (c→0) as secondary reference at 24 °C (−1813.28 ppm).

All

Acknowledgements

We gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.

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C6F5XeF, a versatile starting material in xenon–carbon chemistry

Abstract

Introduction

Section snippets

The substitution of fluorine in 1 by aryl groups

Conclusion

Experimental

Acknowledgements

Int. J. Quant. Chem

J. Am. Chem. Soc

Inorg. Chem

Z. Naturforsch

Angew. Chem. Int. Ed

Organomet

Angew. Chem. Int. Ed

C₆F₅XeF, a versatile starting material in xenon–carbon chemistry