The dioxygenyl

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

, , has been studied in both the gas phase and in salts with anions that cannot be oxidized. The first synthesis was []. Rather than the triple bond of , the bond order is considered to be . Relative to most molecules, this ionization energy is very high at 1175 kJ/mol.Michael Clugston; Rosalind Flemming (2000). ''Advanced Chemistry'', Oxford University Press, , , p. 355. 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 In chemistry, bond order is a formal measure of the multiplicity of a covalent bond between two atoms. As introduced by Gerhard Herzberg, building off of work by R. S. Mulliken and Friedrich Hund, bond order is defined as the difference between t ...

of 2.5, and a

bond length In molecular geometry, bond length or bond distance is defined as the average distance between Atomic nucleus, nuclei of two chemical bond, bonded atoms in a molecule. It is a Transferability (chemistry), transferable property of a bond between at ...

of 112.3 pm in solid O₂ sF₆ It is

isoelectronic Isoelectronicity is a phenomenon observed when two or more molecules have the same structure (positions and connectivities among atoms) and the same electronic configurations, but differ by what specific elements are at certain locations in th ...

with

nitric oxide Nitric oxide (nitrogen oxide, nitrogen monooxide, 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 den ...

and is paramagnetic. The

bond energy In chemistry, bond energy (''BE'') is one measure of the strength of a chemical bond. It is sometimes called the mean bond, bond enthalpy, average bond enthalpy, or bond strength. IUPAC defines bond energy as the average value of the gas-phase b ...

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 (O₂PtF₆), containing the dioxygenyl cation, can be prepared at room temperature by direct reaction of oxygen gas (O₂) with platinum hexafluoride (PtF₆): :O₂ + PtF₆ → 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; it has Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...

sponge at 450 °C, and from oxygen difluoride () above 400 °C: :6 + 2 Pt → 2 + At lower temperatures (around 350 °C), platinum tetrafluoride is produced instead of dioxygenyl hexafluoroplatinate. Dioxygenyl hexafluoroplatinate played a pivotal role in the discovery of

noble gas compound In chemistry, noble gas compounds are chemical compounds that include an element from the noble gases, group 8 or 18 of the periodic table. Although the noble gases are generally unreactive elements, many such compounds have been observed, parti ...

s. The observation that PtF₆ is a powerful enough oxidising agent to oxidise O₂ (which has a first

ionization potential In physics and chemistry, ionization energy (IE) is the minimum energy required to remove the most loosely bound electron of an isolated gaseous atom, positive ion, or molecule. The first ionization energy is quantitatively expressed as :X(g) ...

of 12.2 eV) led Bartlett to reason that it should also be able to oxidise

xenon Xenon is a chemical element; it has 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 The noble gases (historically the inert gases, sometimes referred to as aerogens) are the members of Group (periodic table), group 18 of the periodic table: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn) and, in some ...

xenon hexafluoroplatinate Xenon hexafluoroplatinate is the product of the reaction of platinum hexafluoride with xenon, in an experiment that proved the chemical reactivity of the noble gases. This experiment was performed by Neil Bartlett at the University of British Co ...

. is also found in similar compounds of the form O₂MF₆, where M is

arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

(As),

antimony Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient t ...

(Sb),

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

(Au),

niobium Niobium is a chemical element; it has chemical symbol, symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and Ductility, ductile transition metal. Pure niobium has a Mohs scale of mineral hardness, Mohs h ...

(Nb),

ruthenium Ruthenium is a chemical element; it has symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is unreactive to most chem ...

(Ru),

rhenium Rhenium is a chemical element; it has symbol Re and atomic number 75. It is a silvery-gray, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is one ...

(Re),

rhodium Rhodium is a chemical element; it has 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 isot ...

(Rh),

vanadium Vanadium is a chemical element; it has Symbol (chemistry), symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an ...

(V), or

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

(P). Other forms are also attested, including O₂GeF₅ and (O₂)₂SnF₆. The tetrafluoroborate and hexafluorophosphate salts may be prepared by the reaction of dioxygen difluoride with

boron trifluoride Boron trifluoride is the inorganic compound with the formula . This pungent, colourless, and toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds. Structure and bonding The g ...

or phosphorus pentafluoride at −126 °C: :2 O₂F₂ + 2 BF₃ → 2 O₂BF₄ + F₂ :2 O₂F₂ + 2 PF₅ → 2 O₂PF₆ + F₂ These compounds rapidly decompose at room temperature: :2 O₂BF₄ → 2 O₂ + F₂ + 2 BF₃ :2 O₂PF₆ → 2 O₂ + F₂ + 2 PF₅ Some compounds including O₂Sn₂F₉, O₂Sn₂F₉·0.9HF, O₂GeF₅·HF, and O₂ g(HF)sub>4(SbF₆)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 O₂BF₄ with

at produces a white solid believed to be F–Xe–BF₂, containing an unusual xenon-boron bond: :2 O₂BF₄ + 2 Xe → 2 O₂ + F₂ + 2 FXeBF₂ The dioxygenyl salts O₂BF₄ and O₂AsF₆ react with

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

to give oxalyl fluoride, C₂O₂F₂, in high yield.

References

External links

*{{Commons category-inline, Dioxygenyl Oxycations Oxygen