Organoxenon chemistry

Organoxenon chemistry is the study of the properties of organoxenon compounds, which contain carbon to xenon chemical bonds. The first organoxenon compounds were divalent, such as (C₆F₅)₂Xe. The first tetravalent organoxenon compound, [C₆F₅XeF₂][BF₄], was synthesized in 2004.^[1] So far, more than one hundred organoxenon compounds have been researched.

Most of the organoxenon compounds are more unstable than xenon fluorides due to the high polarity. The molecular dipoles of xenon difluoride and xenon tetrafluoride are both 0 D. The early synthesized ones only contain perfluoro groups, but later some other groups were found, e.g. 2,4,6-trifluorophenyl.^[2]

Organoxenon(II) compounds

The most common bivalent organoxenon compound is C₆F₅XeF, which is almost always used as a precursor to other organoxenon compounds. Due to the instability of xenon(II), it is difficult to synthesize organoxenon compounds by using general organic reagents. Organoxenon compounds are frequently prepared from organocadmium species including Cd(Ar_F)₂ (where Ar_F is a fluorine-containing arene), C₆F₅SiF₃, and C₆F₅SiMe₃ (used along with fluoride).

With the use of stronger Lewis acids, such as C₆F₅BF₂, ionic compounds like [RXe][Ar_FBF₃] can be produced. Alkenyl and alkyl organoxenon compounds are prepared in this way as well, for example, C₆F₅XeCF=CF₂ and C₆F₅XeCF₃.^[2]

Some typical reactions are listed below:

2 C₆F₅XeF + Cd(C₆F₅)₂ → 2 Xe(C₆F₅)₂ + CdF₂↓

C₆F₅XeF + (CH₃)₃SiCN → C₆F₅XeCN + (CH₃)₃SiF

2 C₆F₅XeF + Cd(2,4,6-F₃C₆H₂)₂ → 2 (2,4,6-F₃C₆H₂)XeC₆F₅ + CdF₂↓

The third reaction also produces (C₆F₅)₂Xe, Xe(2,4,6-F₃C₆H₂)₂ and so on.

The precursor C₆F₅XeF can be prepared by the reaction of trimethyl(pentafluorophenyl)silane (C₆F₅SiMe₃) and xenon difluoride. Adding fluoride to the adduct of C₆F₅XeF and arsenic pentafluoride is another method.^[2]

Arylxenon compounds with fewer fluorine substituents are also known. For instance, (2,6-F₂C₆H₃)Xe⁺BF⁻
₄ and (4-FC₆H₄)Xe⁺BF⁻
₄ have been prepared, and a crystal structure of the former has been obtained, consisting of a formally 1-coordinate xenon with a long, weak contact with a fluorine on the tetrafluoroborate anion.^[3][4]

Organoxenon(IV) compounds

In 2000, Karel Lutar and Boris Žemva et al. produced an ionic compound. They treated xenon tetrafluoride and difluoro(pentafluorophenyl)borane in dichloromethane at −55 °C:

XeF₄ + C₆F₅BF₂ DCM→ [C₆F₅XeF₂]⁺BF⁻
₄

The compound is an extremely strong fluorinating agent, and it is capable of converting (C₆F₅)₃P to (C₆F₅)₃PF₂, C₆F₅I to C₆F₅IF₂, and iodine to iodine pentafluoride.^[1]

References