The dioxygenyl
ion, , is a rarely-encountered
oxycation
In chemistry, an oxycation is a polyatomic ion with a positive charge that contains oxygen.
Examples
* Dioxygenyl ion,
* Nitrosonium ion,
* Nitronium ion,
* Vanadyl ion, VO2+, a very stable oxycation
* Uranyl ion, , all natural U6+ occurs ...
in which both
oxygen atoms have a formal
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
of . It is formally derived from
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
by the removal of an
electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have n ...
:
:O
2 → + e
−
The energy change for this process is called the
ionization energy of the oxygen molecule. Relative to most molecules, this ionization energy is very high at 1175 kJ/mol. As a result, the scope of the chemistry of is quite limited, acting mainly as a 1-electron oxidiser.
Structure and molecular properties
has a
bond order of 2.5, and a
bond length of 112.3 pm in solid O
2 sF6 It is
isoelectronic with
nitric oxide
Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its ...
and is paramagnetic. The
bond energy is 625.1 kJ mol
−1 and the stretching frequency is 1858
cm−1,
both of which are high relative to most of the molecules.
Synthesis
Neil Bartlett demonstrated that
dioxygenyl hexafluoroplatinate (O
2PtF
6), containing the dioxygenyl cation, can be prepared at room temperature by direct reaction of oxygen gas (O
2) with
platinum hexafluoride (PtF
6):
:O
2 + PtF
6 →
The compound can also be prepared from a mixture of fluorine and oxygen gases in the presence of a
platinum
Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver".
Pla ...
sponge at 450 °C, and from
oxygen difluoride () above 400 °C:
:6 + 2 Pt → 2 +
At lower temperatures (around 350 °C),
platinum tetrafluoride
Platinum tetrafluoride is the inorganic compound with the chemical formula . In the solid state, the compound features platinum(IV) in octahedral coordination geometry.
Preparation
The compound was first reported by Henri Moissan by the fluorinat ...
is produced instead of dioxygenyl hexafluoroplatinate.
Dioxygenyl hexafluoroplatinate played a pivotal role in the discovery of
noble gas compounds. The observation that PtF
6 is a powerful enough oxidising agent to oxidise O
2 (which has a first
ionization potential of 12.2
eV) led Bartlett to reason that it should also be able to oxidise
xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
(first ionization potential 12.13 eV). His subsequent investigation yielded the first compound of a
noble gas,
xenon hexafluoroplatinate.
is also found in similar compounds of the form O
2MF
6, where M is
arsenic
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, b ...
(As),
antimony
Antimony is a chemical element with the symbol Sb (from la, stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient ti ...
(Sb),
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
(Au),
niobium (Nb),
ruthenium (Ru),
rhenium (Re),
rhodium
Rhodium is a chemical element with the symbol Rh and atomic number 45. It is a very rare, silvery-white, hard, corrosion-resistant transition metal. It is a noble metal and a member of the platinum group. It has only one naturally occurring i ...
(Rh),
vanadium (V),
or
phosphorus
Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ea ...
(P).
Other forms are also attested, including O
2GeF
5 and (O
2)
2SnF
6.
The tetrafluoroborate and hexafluorophosphate salts may be prepared by the reaction of
dioxygen difluoride with
boron trifluoride or
phosphorus pentafluoride at −126 °C:
:2 O
2F
2 + 2 BF
3 → 2 O
2BF
4 + F
2
:2 O
2F
2 + 2 PF
5 → 2 O
2PF
6 + F
2
These compounds rapidly decompose at room temperature:
:2 O
2BF
4 → 2 O
2 + F
2 + 2 BF
3
:2 O
2PF
6 → 2 O
2 + F
2 + 2 PF
5
Some compounds including O
2Sn
2F
9, O
2Sn
2F
9·0.9HF, O
2GeF
5·HF, and O
2 g(HF)sub>4(SbF
6)
9 can be made by ultraviolet irradiation of oxygen and fluorine dissolved in anhydrous hydrogen fluoride with a metal oxide.
All attempts to prepare with chloro anions like met with failure.
Reactions
The reaction of O
2BF
4 with
xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
at produces a white solid believed to be F–Xe–BF
2, containing an unusual xenon-boron bond:
:2 O
2BF
4 + 2 Xe → 2 O
2 + F
2 + 2 FXeBF
2
The dioxygenyl salts O
2BF
4 and O
2AsF
6 react with
carbon monoxide
Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simpl ...
to give
oxalyl fluoride, C
2O
2F
2, in high yield.
References
External links
*{{Commonscatinline, Dioxygenyl
Oxycations
Oxygen