Noble‐Gas Compounds

Abstract

Noble‐gas reactivity was discovered on March 23, 1962 when Neil Bartlett (1932–2008) showed that xenon gas was oxidized by PtF 6 . The product obtained by Bartlett was initially formulated as XePtF 6 . Pursuant to his discovery, numerous xenon and krypton compounds were synthesized in macroscopic quantities. Among the noble‐gas elements, xenon has the most extensive chemistry, and it can possess formal oxidation states of 0, +2, +4, +6, and +8 in its compounds by forming fluorides, oxides, and oxide fluorides, as well as derivatives in which xenon is bonded to polyatomic groups through oxygen, nitrogen, and carbon. In addition, compounds containing Xe–Au, Xe–Xe, Xe–Cl, and Hg–Xe bonds are known. Other xenon‐element bonds are known in the gas phase or in low‐temperature matrices, which are exemplified by Xe–H, Xe–Si, Xe–S, Xe–X (X=Cl, Br, I), and Xe–U bonds. Krypton chemistry is more limited. Only compounds with krypton in the +2 oxidation state are known, namely, KrF 2 , salts of the KrF + and Kr 2 F 3 + cations, by analogy with xenon, the Kr–O bonded compound, Kr(OTeF 5 ) 2 , and several species containing Kr–N bonds. Several gas‐phase and matrix‐isolated species in which krypton is bonded to carbon, hydrogen, and halides other than fluorine are also known. Radon is believed to form RnF 2 and RnF + by analogy with krypton and xenon. The only argon species that are known are the ArF + cation, which has been observed in the gas phase, and HArF, which has been stabilized in a low‐temperature argon matrix. To date, no argon, neon, or helium compounds have been isolated in macroscopic amounts. Noble‐gas compounds have been used as oxidizers and as oxidative fluorinating agents in chemical syntheses.

The Chemistry of Xenon(IV)

“…Although many xenon compounds in the II and VI oxidation states have been synthesized, the chemistry of Xe­(IV) and its compounds is less developed. , Several factors have contributed to the relative scarcity of Xe­(IV) compounds: their strong oxidant properties, the endothermic natures of the oxide and oxide fluoride derivatives, and their tendencies to undergo redox eliminations and disproportionations. − …”

[H(OXeF2)n][AsF6] and [FXeII(OXeIVF2)n][AsF6] (n = 1, 2): Examples of Xenon(IV) Hydroxide Fluoride and Oxide Fluoride Cations and the Crystal Structures of [F3Xe---FH][Sb2F11] and [H5F4][SbF6]·2[F3Xe---FH][Sb2F11]

“…Although many compounds containing xenon in the +2 and +6 oxidation states are known, far fewer Xe(IV) compounds are known. 1,2 Among the factors that contribute to the relative scarcity of Xe(IV) compounds is the propensity for the oxide and oxide fluorides to undergo redox eliminations and disproportionations to Xe(II) and O 2 , or to Xe(II) and Xe(VI). 3−6 Examples of Xe(IV) cations are presently limited to C 6 F 5 XeF 2 + , 7 XeF 3 + , 8−15 and F x Xe(OTeF 5 ) 3−x + (x = 0−2).…”

“…Although many compounds containing xenon in the +2 and +6 oxidation states are known, far fewer Xe(IV) compounds are known. , Among the factors that contribute to the relative scarcity of Xe(IV) compounds is the propensity for the oxide and oxide fluorides to undergo redox eliminations and disproportionations to Xe(II) and O 2 , or to Xe(II) and Xe(VI). − Examples of Xe(IV) cations are presently limited to C 6 F 5 XeF 2 + , XeF 3 + , − and F x Xe(OTeF 5 ) 3– x + ( x = 0–2) . Although several examples of cations containing more than one xenon atom are known, namely, those of Xe(II) (Xe 2 F 3 + , , Xe 3 OF 3 + ,), Xe(VI) (Xe 2 F 11 + , , F(O) 2 Xe---F---Xe(O) 2 F + ), and the mixed-oxidation state coordination complexes XeF 2 ·XeF 5 + , 2XeF 2 ·XeF 5 + , XeF 2 ·2XeF 5 + , and XeF 2 ·XeF 4 ·Mg 2+ , polynuclear cations of Xe(IV) are unknown.…”

A new krypton complex – experimental and computational investigation of the krypton sulphur pentafluoride cation, [KrSF5]+, in the gas phase

“…Only xenon and, partially, krypton have a chemistry accessible under ordinary conditions. 1,6–9 The xenon fluorides, XeF n , such as the difluoride, tetrafluoride, and hexafluoride, as well as xenon oxide tetrafluoride, XeOF 4 , are thermodynamically stable. Although the first krypton compound to be prepared was described as the tetrafluoride, 10 the properties ascribed to it were later shown to be those of the difluoride.…”