Disulfur dioxide
Chemical compound From Wikipedia, the free encyclopedia
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]
| |
 | |
| Names | |
|---|---|
| Other names
disulfur(II)oxide SO dimer | |
| Identifiers | |
3D model (JSmol) |
|
PubChem CID |
|
| |
| |
| 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).
| |
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]
The electronic ground state is a singlet, unlike disulfur or dioxygen.[6]
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.[7]
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:[8]
- S + SO2 → S2O2 ⇌ 2 SO
Disulfur dioxide is also produced upon a microwave discharge in sulfur dioxide diluted in helium.[9] At a pressure of 0.1 mmHg (13 Pa), five percent of the result is S2O2.[10]
Disulfur dioxide is formed transiently when hydrogen sulfide and oxygen undergo flash photolysis.[11]
A branched isomer isoelectronic to SO3, S=SO2, is believed to form during the thermal decomposition of cyclic vicinal alkyl thiosulfites.[12]
Properties
The ionization energy of disulfur dioxide is 9.93±0.02 eV.[7]
Disulfur dioxide absorbs at 320–400 nm, as observed of the Venusian atmosphere,[13] and is believed to have contributed to the greenhouse effect on that planet.[14]
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.[9][15]
Decomposition of S2O2 proceeds via the following disproportionation reaction:
- S2O2 → SO2 + 1/8 S8
Complexes
S2O2 can be a ligand with transition metals. It binds in the η2-S–S position with both sulfur atoms linked to the metal atom.[16] This was first shown in 2003. The bis(trimethylphosphine) thiirane S-oxide complex of platinum, when heated in toluene at 110 °C loses ethylene, and forms a complex with S2O2: (Ph3P)2Pt(S2O2).[17] 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.[18][19] 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.[18]
Anion
The S
2O−
2 radical anion has been observed in the gas phase. It may adopt a trigonal shape akin to SO3.[20]
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.[13] It is not found in any substantive quantity in Earth's atmosphere.
References
Wikiwand - on
Seamless Wikipedia browsing. On steroids.