What is the form of XeF3

content1 Introduction 2. hydrogen3. Noble gases4. Halogens5. Chalcogens6. Pentele7. Tetrele8. Boron
The following table gives an overview of the most important and simplest noble gas compounds. Almost all of them are Xe compounds, only KrF2 can still be mentioned as a reasonably tangible connection. The most important Xe-F ions are also listed.
+2 XeF+ XeF2
+4 XeF3+ XeF4 XeF5- XeOF2
+6 XeF6 XeF7- XeF82- XeO3 XeO42- XeO2F.2 XeOF4
+8 XeO4 XeO52- XeO64- XeO3F.2 XeO2F.4
Tab. 3.3.1. Xe fluorides and oxides (each with ions) as well as mixed Xe oxide fluorides
The fluoride XeF is known from Xe2 (Mp: 129 OC), XeF4 (Mp: 117 OC) and XeF6 (Mp: 49.5 OC). Also KrF2 and RnF2 are known, but only the Xe fluorides are thermodynamically stable. XeF4 and XeF6 are sensitive to hydrolysis, but XeF is2 even for some time in H2O stable. The stability of the compounds generally decreases with the fluorine content, XeF6 acts as a fluorinating agent.

The Xe fluorides can generally be explained according to the VSEPR concept. After that is XeF2 linear (three free electron pairs), XeF4 built in a square planar manner. XeF6 is ionic in the solid state as [XeF5]+ + F- before (see Fig. 3.3.1), in the gas it has an octahedral shape as a molecule, i.e. the influence of the lone pair of electrons is missing here.

Fig. 3.3.1. XeF crystal structures6 and [(CH3)4N+] [XeF5-]

This is achieved from the elements by pressure fluorination, e.g. according to:

Xe + 3 F2 ---> XeF6
at a temperature of 400 OC, 60 bar pressure and an Xe: F ratio of 1:40. Higher fluorides can be obtained from the lower compounds:
XeF4 + F2 ---> XeF6

How important are the noble gas fluorides:

  • the fluorinating effect, especially of XeF6:
    XeF4 + 2 H.2 ---> 130OC ---> Xe + 4 HF
  • the oxidizing effect, especially of XeF2 and XeF4:
    2 cl- ---> Cl2 + 2 e-
    in which elementary Xe is formed:
    XeF2 + 2 e- ---> Xe + 2 F-
  • salt formation, which can also be described as an acid-base reaction. I.e. the effect of the Xe fluoride:
    • as F-Donor:
      BF3 + XeF6 <---> [XeF5]+ + [BF4]-
      AsF5 + XeF6 <---> [XeF5]+ + [AsF6]-
    • as F-Acceptor:
      XeF6 + CsF ---> CsXeF7 ---> Cs2XeF8
  • as well as substitutions of the F ligands:
    XeF6 + HSO3F ---> F5XeOSO2F + HF
ATTENTION when working with Xe fluorides. These compounds react with quartz according to
2 XeF6 + SiO2 ---> 2 XeOF4 + SiF4
to oxides or oxide fluorides, which are very explosive (see below). The Xe oxides Xe are knownVIO3 and XeVIIIO4.

They do not succeed directly from the elements, but

  • in the case of XeO3 by hydrolysis of the fluorides:
    3 XeIVF.4 + 6 H.2O ---> Xe0 + 12 HF + XeVIO3
    XeF6 + 3 H.2O ---> XeO3 + 6 HF
  • for XeO4 made of Ba perxenate (VIII) (Ba2[XeO6]) by dewatering with H2SO4:
    XeO64- + 4 H.+ ---> H4XeO6 ---> XeO4 + 2 H.2O
    The source for the Perxenate (VIII) is XeO3, which disproportionates with excess base:
    2 HXeO4- ---> [XeVIIIO4]2- + Xe0 + O2
  • XeO3 is a colorless, very explosive solid. They are molecular crystals, the molecule is isoelectronic and isostructural to IO3-. When exposed to bases and heating, xenate (VI) is formed:
    XeVIO3 + Ba (OH)2 ---> XeVIO42-
    If there is an excess of base, disproportionation occurs with the formation of elementary Xe and perxenate (VIII):
    2 HXeO4- ---> [XeVIIIO4]2- + Xe0 + O2
    Perxenates disintegrate when concentrated H is added2SO4 to XeO4.
  • XeO4 is a colorless already at -40 OC explosive gas. The molecule is isoelectronic and isostructural to IO4- and like this has an ideal tetrahedral shape (point group -43m). The corresponding salts are the Perxenate XeO64-.
The oxide fluorides of xenon XeF are known4O, XeF2O, XeF2O2, XeF2O3which are very unstable except for the former. They arise during the hydrolysis of the corresponding fluorides; the structure of the molecules can be determined with the help of the VSEPR theory, Chap. 3.4. can be derived. There are also Xe compounds with Xe-O, Xe-N and Xe-C bonds, e.g.
  • Xe-O bond in O-Xe (OTeF5)4 (large groups EN!)
  • Xe-N bond in F-Xe-N (SO2F)2
  • Xe-C bond in +[Xe-C6F.5] (only up to -40 OC stable) and in the crystal structure of the salt with [BF4]--Anion.
  • Xe can even act as a ligand in gold complexes.
As with all covalent compounds and e.g. already with hydrogen H2 in chapter 2.1. called, the chemical bond in the noble gas compounds can be described with different models:
  • The VSEPR theory (Section 3.4.) Allows the structure of the molecules to be determined without details of the chemical bonds.
  • In the VB description hybridization with the d orbitals is necessary to explain the stabilities, but according to current knowledge this has little or no significance.
  • The MO theory allows the most comprehensive description of bond and stability. In the case of the noble gas compounds, however, it is a matter of hypervalent compounds (exceeding the octet rule), which only after getting used to the MO description for the halogens and oxygen using the example of the chemical bond in SF6 to be discussed in the case of sulfur.
content1 Introduction 2. hydrogen3. Noble gases4. Halogens5. Chalcogens6. Pentele7. Tetrele8. Boron