Disulfur dioxide

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Disulfur dioxide
structure of disulfur dioxide, S2O2
space-filling model of the disulfur dioxide molecule
Names
Other names
disulfur(II)oxide
SO dimer
Identifiers
3D model (
JSmol
)
  • InChI=1/O2S2/c1-3-4-2
    Key: AXYLJRYHRATPSG-UHFFFAOYNA-N
  • O=[S][S]=O
Properties
S2O2
Molar mass 96.1299 g/mol
Appearance gas
Structure
bent
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 toxic
Related compounds
Related compounds
tetrasulfur
SO,
S3O
S2O
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Disulfur dioxide, dimeric sulfur monoxide or SO dimer is an oxide of sulfur with the formula S2O2.[2] The solid is unstable with a lifetime of a few seconds at room temperature.[3]

Structure

Disulfur dioxide adopts a

cis planar structure with C2v symmetry. The S−O bond length is 145.8 pm, shorter than in sulfur monoxide. The S−S bond length is 202.45 pm and the O−S−S angle is 112.7°. S2O2 has a dipole moment of 3.17 D.[4] It is an asymmetric top molecule.[1][5]

Formation

Sulfur monoxide (SO) converts to disulfur dioxide (S2O2) spontaneously and reversibly.[4] So the substance can be generated by methods that produce sulfur monoxide. Disulfur dioxide has also been formed by an electric discharge in sulfur dioxide.[5] Another laboratory procedure is to react oxygen atoms with carbonyl sulfide or carbon disulfide vapour.[6]

Although most forms of elemental sulfur (S8 and other rings and chains) do not combine with SO2, atomic sulfur does so to form sulfur monoxide, which dimerizes:[7]

S + SO2 → S2O2 ⇌ 2 SO

Disulfur dioxide is also produced upon a microwave discharge in sulfur dioxide diluted in helium.[8] At a pressure of 0.1 mmHg (13 Pa), five percent of the result is S2O2.[9]

Disulfur dioxide is formed transiently when hydrogen sulfide and oxygen undergo flash photolysis.[10]

Properties

The ionization energy of disulfur dioxide is 9.93±0.02 eV.[6]

Disulfur dioxide absorbs at 320–400 nm, as observed of the Venusian atmosphere,[11] and is believed to have contributed to the greenhouse effect on that planet.[12]

Reactions and decomposition

Although disulfur dioxide exists in equilibrium with sulfur monoxide, it also reacts with sulfur monoxide to form sulfur dioxide and disulfur monoxide.[8][13]

Decomposition of S2O2 proceeds via the following

disproportionation reaction
:

S2O2 → SO2 + 1/8 S8

Complexes

S2O2 can be a

thiirane S-oxide complex of platinum, when heated in toluene at 110 °C loses ethylene, and forms a complex with S2O2: (Ph3P)2Pt(S2O2).[15] Iridium atoms can also form a complex: cis-[(dppe)2IrS2]Cl with sodium periodate oxidizes to [(dppe)2IrS2O] and then to [(dppe)2IrS2O2], with dppe being 1,2-bis(diphenylphosphino)ethane.[16][17] This substance has the S2O2 in a cis position. The same conditions can make a trans complex, but this contains two separate SO radicals instead. The iridium complex can be decomposed with triphenylphosphine to form triphenylphosphine oxide and triphenylphosphine sulfide.[16]

Anion

The S
2O−
2 radical

trigonal shape akin to SO3.[18]

Spectrum

Microwave

Transition Frequency (MHz)[5]
21,1−20,2 11013.840
41,3−40,4 14081.640
11,1−00,0 15717.946
40,4−31,3 16714.167
31,3−20,2 26342.817
42,2−41,3 26553.915
22,0−21,1 28493.046
60,6−51,5 30629.283
52,4−51,5 35295.199
51,5−40,4 35794.527

In the Solar System

There is some evidence that disulfur dioxide may be a small component in the atmosphere of Venus, and that it may substantially contribute of the planet's severe greenhouse effect.[11] It is not found in any substantive quantity in Earth's atmosphere.

References

  1. ^
    ISBN 9783642141454
    .
  2. ISBN 9780123526519
    .
  3. ISBN 9780203362525
    .
  4. ^
    doi:10.1063/1.1681015
    .
  5. ^
    doi:10.1016/j.molstruc.2006.02.055
    .
  6. ^
    ISSN 0021-9606
    .
  7. ISSN 1089-5639
    .
  8. ^
    S2CID 122789729. Archived from the original
    (PDF) on 2015-09-24. Retrieved 2013-05-13.
  9. ISBN 9788120343085
    . Retrieved 2013-05-16.
  10. ISBN 9780080868011
    .
  11. ^
    doi:10.1002/2016GL070916
    .
  12. ^ "Rare molecule on Venus may help explain planet's weather". CBC News. Retrieved 2016-11-11.
  13. doi:10.1016/0009-2614(80)87032-1
    .
  14. ISSN 0020-1669. Archived from the original
    (PDF) on 2015-11-06. Retrieved 2013-05-13.
  15. ISSN 0570-0833
    .
  16. ^
    ISSN 0009-2940
    .
  17. ISSN 0366-7022
    .
  18. ISSN 1089-5639
    . Retrieved 2013-05-13.
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