Disulfur dioxide, dimeric sulfur monoxideorSO dimer is an oxideofsulfur with the formula S2O2.[2] The solid is unstable with a lifetime of a few seconds at room temperature.[3]
Disulfur dioxide adopts a cis planar structure with C2vsymmetry. 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]
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 sulfideorcarbon 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]
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.[14] 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).[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]
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.
^Holleman, Arnold F.; Wiber, Egon; Wiberg, Nils, eds. (2001). "Oxides of sulfur". Inorganic Chemistry. Academic Press. p. 530. ISBN9780123526519.
^Mitchell, Stephen C. (2004). Biological Interactions Of Sulfur Compounds. CRC Press. p. 7. ISBN9780203362525.
^ abLovas, F. J. (1974). "Spectroscopic studies of the SO2 discharge system. II. Microwave spectrum of the SO dimer". The Journal of Chemical Physics. 60 (12): 5005. Bibcode:1974JChPh..60.5005L. doi:10.1063/1.1681015.
^Compton, R. G.; Bamford, C. H.; Tipper, C. F. H. (1972). "Oxidation of H2S". Reactions of Non-Metallic Inorganic Compounds. Comprehensive Chemical Kinetics. Elsevier. p. 50. ISBN9780080868011.
^Herron, J. T.; Huie, R. E. (1980). "Rate constants at 298 K for the reactions SO + SO + M → (SO)2 + M and SO + (SO)2 → SO2 + S2O". Chemical Physics Letters. 76 (2): 322–324. Bibcode:1980CPL....76..322H. doi:10.1016/0009-2614(80)87032-1.
^Lorenz, Ingo-Peter; Kull, Jürgen (1986). "Complex Stabilization of Disulfur Dioxide in the Fragmentation of Thiirane S-Oxide on Bis(triphenylphosphane)platinum(0)". Angewandte Chemie International Edition in English. 25 (3): 261–262. doi:10.1002/anie.198602611. ISSN0570-0833.
^ abSchmid, Günter; Ritter, Günter; Debaerdemaeker, Tony (1975). "Die Komplexchemie niederer Schwefeloxide. II. Schwefelmonoxid und Dischwefeldioxid als Komplexliganden" [The complex chemistry of lower sulfur oxides. II. Sulfur monoxide and disulfur dioxide as complex ligands]. Chemische Berichte. 108 (9): 3008–3013. doi:10.1002/cber.19751080921. ISSN0009-2940.
^Nagata, K.; Takeda, N.; Tokitoh, N. (2003). "Unusual Oxidation of Dichalcogenido Complexes of Platinum". Chemistry Letters. 32 (2): 170–171. doi:10.1246/cl.2003.170. ISSN0366-7022.
