A Rare Example of a Krypton Difluoride Coordination Compound: [BrOF 2 ][AsF 6 ]·2KrF 2

Breddemann

et al. 2019

Chemistry A European J

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The noble‐gas difluoride adducts, NgF2⋅CrOF4 and NgF2⋅2CrOF4 (Ng=Kr and Xe), have been synthesized and structurally characterized at low temperatures by Raman spectroscopy and single‐crystal X‐ray diffraction. The low fluoride ion affinity of CrOF4 renders it incapable of inducing fluoride ion transfer from NgF2 (Ng=Kr and Xe) to form ion‐paired salts of the [NgF]+ cations having either the [CrOF5]− or [Cr2O2F9]− anions. The crystal structures show the NgF2⋅CrOF4 adducts are comprised of Ft−Ng−Fb‐ ‐ ‐Cr(O)F4 structural units in which NgF2 is weakly coordinated to CrOF4 by means of a fluorine bridge, Fb, in which Ng−Fb is elongated relative to the terminal Ng−Ft bond. In contrast with XeF2⋅2MOF4 (M=Mo or W) and KrF2⋅2MoOF4, in which the Lewis acidic, F4(O)M‐ ‐ ‐Fb‐ ‐ ‐M(O)F3 moiety coordinates to Ng through a single M‐ ‐ ‐Fb−Ng bridge, both fluorine ligands of NgF2 coordinate to CrOF4 molecules to form F4(O)Cr‐ ‐ ‐Fb−Ng−Fb‐ ‐ ‐Cr(O)F4 adducts in which both Ng−Fb bonds are only marginally elongated relative to the Ng−F bonds of free NgF2. Quantum‐chemical calculations show that the Cr−Fb bonds of NgF2⋅CrOF4 and NgF2⋅2CrOF4 are predominantly electrostatic with a small degree of covalent character that accounts for their nonlinear Cr‐ ‐ ‐Fb−Ng bridge angles and staggered O−Cr‐ ‐ ‐Fb−Ng−Ft dihedral angles. The crystal structures and Raman spectra of two CrOF4 polymorphs have also been obtained. Both are comprised of fluorine‐bridged chains that are cis‐ and trans‐fluorine‐bridged with respect to oxygen.

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Section: Raman Spectroscopysupporting

confidence: 81%

Section: A-crof 4 and B-crofmentioning

confidence: 99%

Section: A-crof 4 and B-crofmentioning

confidence: 99%

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Syntheses, Structures, and Bonding of NgF₂⋅CrOF₄, NgF₂⋅2CrOF₄(Ng=Kr, Xe), and (CrOF₄)_∞

Breddemann

et al. 2019

Chemistry A European J

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“…(105,195). The only example presently known in which KrF 2 coordinates to a main-group center is [BrOF 2 ][AsF 6 ]Á2KrF 2 [1217521- and is the only coordination compound of KrF 2 that has been structurally characterized by x-ray crystallography (196).…”

Section: Krypton Compoundsmentioning

confidence: 99%

Noble‐Gas Compounds

Schrobilgen

Kirk-Othmer Encyclopedia of Chemical Technology

2012

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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.

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“…A considerable number of metal cations exhibiting this behavior towards XeF 2 have been synthesized and structurally characterized. Recent reviews outlining progress in this area [9,10] [20], Xe [21]) have been reported which contain NgF 2 molecules that are terminally coordinated to bromine(V) through fluorine. The Ng-F stretching frequencies of main-group cation complexes with NgF 2 show frequency shift patterns that are similar to those of the metal cation complexes (vide supra).…”

Section: Introductionmentioning

confidence: 99%

A Raman spectroscopic study of the XeOF4/XeF2 system and the X-ray crystal structure of α-XeOF4·XeF2

Hughes

Journal of Fluorine Chemistry

et al. 2011

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