Disulfur monoxide
Encyclopedia
Disulfur monoxide or sulfur suboxide is an unstable gas being a compound of sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

 and oxygen with formula S2O. It is one of the lower sulfur oxides
Lower sulfur oxides
The lower sulfur oxides are a group of chemical compounds consisting of :*SO, sulfur monoxide and its dimer S2O2*S2O*sulfur monoxides, SnO, based on cyclic Sn rings where n is 5-10*S7O2*polymeric oxides, polysulfuroxides sometimes termed PSO's...

. It is a colourless gas. It can be formed by reacting thionyl chloride
Thionyl chloride
Thionyl chloride is an inorganic compound with the formula SOCl2. It is a reactive chemical reagent used in chlorination reactions. It is a colorless, distillable liquid at room temperature and pressure that decomposes above 140 °C. Thionyl chloride is sometimes confused with sulfuryl...

 with silver sulfide
Silver sulfide
Silver sulfide, Ag2S, is the sulfide of silver. This dense black solid constitutes the tarnish that forms over time on silverware and other silver objects. Silver sulfide is insoluble in all solvents, but is degraded by strong acids. Silver sulfide features a covalent bond, as it is made up of...

:
SOCl2 + Ag2S AgCl
Silver chloride
Silver chloride is a chemical compound with the chemical formula AgCl. This white crystalline solid is well known for its low solubility in water . Upon illumination or heating, silver chloride converts to silver , which is signalled by greyish or purplish coloration to some samples...

 + S2O.


This is done under low pressure and high temperature. Another way to form it is via a glow discharge in sulfur dioxide
Sulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...

. The arrangement of atoms is SSO in a bent form. The angle formed at the central sulfur atom is 117.88°. The sulfur to sulfur bond length is 188.4pm, and the length of the oxygen bond is 188.4pm. It can form an orange red condensate at liquid nitrogen temperatures. On decomposition at room temperature it forms SO2 and polysulfur oxide.

It is the base oxide for thiosulfurous acid. The formal oxidation state for sulfur is +1, however sulfur plays two different roles in the molecule.

Discovery

The gas was first produced by P. W. Schenk in 1933 with a glow discharge though sulfur vapour and sulfur dioxide. He discovered that the gas could survive for hours at single digit pressures of mercury in clean glass, but decomposed when the pressure went up to 30mm of mercury. However he believed that the formula was SO and called it sulfur monoxide
Sulfur monoxide
Sulfur monoxide is an inorganic compound with formula . It is only found as a dilute gas phase. When concentrated or condensed, it converts to S2O2 . It has been detected in space but is rarely encountered intact otherwise.-Structure and bonding:The SO molecule has a triplet ground state similar...

. In 1940 K Kondrat'eva and V Kondrat'ev became convinced that the formula was S2O2, disulfur dioxide. However all were wrong until in 1956, David J. Meschi and Rollie J. Myers proved the formula was S2O.

Natural occurrence

Desulfovibrio
Desulfovibrio
Desulfovibrio is a genus of Gram negative sulfate-reducing bacteria. Some species of Desulfovibrio are capable of transduction. Desulfovibrio species are commonly found in aquatic environments with high levels of organic material, as well as in water-logged soils, and form major community members...

 desulfuricans
is claimed to produce S2O.
S2O can be found coming from volcanoes on Io
IO
Io, IO, I/O, i/o, or i.o. may refer to:-An abbreviation:* I.O., a theater in Chicago, Illinois dedicated to improvisational comedy* i.o., "in illo ordine", Latin phrase meaning "respectively"...

. It can form from 1 to 6% when hot 100 bar S2 and SO2 gas erupts from volcanoes. It is believed that Pele
Pele (volcano)
Pele is an active volcano on the surface of Jupiter's moon Io. It is located on Io's trailing hemisphere at A large, tall volcanic plume has been observed at Pele by various spacecraft starting with Voyager 1 in 1979, though it has not been persistent. The discovery of the Pele plume on March...

 on Io is surrounded by solid S2O.

Reactions

A self decomposition can from trithio-ozone S3 and S2O. Also 5,6-di-tert-butyl-2,3,7-trithiabicyclo[2.2.1]hept-5-ene 2-endo-7-endo-dioxide when heated can form S2O. It reacts with diazoalkanes for form dithiirane 1-oxides.

Disulfur monoxide can be a ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...

 bound to transition metal
Transition metal
The term transition metal has two possible meanings:*The IUPAC definition states that a transition metal is "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transition metals in this definition.*Some...

s. These are formed by oxidation with dioxygen for a disulfur ligand complex. Excessive oxygen can yield a dioxygendisulfur ligand, which can be reduced in turn with triphenylphosphine
Triphenylphosphine
Triphenylphosphine is a common organophosphorus compound with the formula P3 - often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature...

. Examples are: [Ir(dppe)2S2O]+, OsCl(NO)(PPh3)2S2O NbCl(η-C5H5)2S2O Mn(CO)2(η-C5Me5)S2O Re(CO)2(η-C5Me5)S2O Re(CO)2(η-C5H5)S2O.

More complex nucleations occur with transition metal ligand combinations. With molybdenum Mo(CO)2(S2CNEt2)2 reacts with elemental sulfur and air to form a compound Mo2(S2O)2(S2CNEt2)4. Another way to form these complexes is to combine iminooxosulfurane (OSNSO2.R) complexes with hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

. Complexes formed in this way are: IrCl(CO)(PPh3)2S2O; Mn(CO)2(η-C5H5)S2O. With hydrosulfide and a base followed by oxygen, OsCl(NO)(PPh3)2S2O can be made.
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