Disulfur monoxide: Difference between revisions

Disulfur monoxide
Names
	Other names sulfur suboxide; sulfuroxide;
Identifiers
CAS Number	20901-21-7 ;
3D model (JSmol)	Interactive image;
ChemSpider	124163;
PubChem CID	140772;
CompTox Dashboard (EPA)	DTXSID90175054 ;
	InChI : InChI=1S/OS2/c1-3-2 Key: TXKMVPPZCYKFAC-UHFFFAOYSA-N;
	SMILES O=S=S;
Properties
Chemical formula	S2O
Molar mass	80.1294 g/mol
Appearance	colourless gas or dark red solid
Structure
Coordination geometry	bent
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	toxic
Related compounds
Related compounds	Trisulfur; SO; Ozone; SO2
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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Disulfur monoxide or sulfur suboxide is an inorganic compound with the formula S₂O, one of the lower sulfur oxides. It is a colourless gas and condenses to give a roughly dark red coloured solid that is unstable at room temperature.

S
₂O occurs rarely in natural atmospheres, but can be made by a variety of laboratory procedures. For this reason, its spectroscopic signature is very well understood.

Structure and spectrum

Like sulfur dioxide (and, indeed, most molecules) but unlike sulfur monoxide, disulfur, or dioxygen, the ground state of disulfur monoxide is a singlet.^[3]^[4]

Condensed solid S₂O absorbs at 420 nm (roughly indigo) and 530 nm (roughly lime). These bands have been assigned to decomposition products S₃ and S₄.^[5]

In the ultraviolet, S₂O has absorption band systems in the ranges 250–340 nm and 190–240 nm. There are bands at 323.5 and 327.8 nm.^[6] The band in the 315–340 nm range is due to the C¹A′–X¹A′ (π* ← π) transition.^[7]

Gaseous disulfur monoxide does not absorb light in the visible spectrum.

The microwave spectrum of S₂O has the following rotational parameters: A = 41915.44 MHz, B = 5059.07 MHz, and C = 4507.19 MHz.^[8] Moreover, the microwave spectrum suggests the S−S−O angle is 117.88° with S−S and S−O bond lengths of 188.4 and 146.5 pm, respectively.^[9] In the 327.8 nm excited state, the central angle tightens to 109°.^[6]

The harmonic frequency for S−S stretching is 415.2 cm⁻¹.^[7]

Synthesis

Historical

Disulfur monoxide was discovered by Peter W. Schenk in 1933^[10] 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 it decomposed near 30 mmHg (4 kPa). Schenk assigned the formula as SO and called it sulfur monoxide. In 1956, D. J. Meschi and R. J. Myers established the formula as S₂O.^[11]

Preparation

Oxidizing sulfur with copper(II) oxide:^[12]^[13]

3 S₈ + 12 CuO → 12 CuS + 4 S₂O + 4 SO₂

A relatively pure generator is the reaction of thionyl chloride with silver(I) sulfide:^[14]

SOCl₂ + Ag₂S → 2 AgCl + S₂O

Also 5,6-di-tert-butyl-2,3,7-trithiabicyclo[2.2.1]hept-5-ene 2-endo-7-endo-dioxide decomposes upon heating with release of S₂O:^[15]

Occurrence

Volcanism

Volcanoes on Io produce substantial quantities of S
₂O. It can form between 1% and 6% when hot 100-bar S₂ and SO₂ gas erupts from volcanoes. It is believed that Pele on Io is surrounded by solid S₂O.^[16]

Terran atmosphere

Disulfur monoxide is too unstable to survive at standard conditions,^[10] but transient sources include incomplete combustion of sulfur vapor^[17] and thermal decomposition of sulfur dioxide in a glow discharge.^[18]

As a ligand

Disulfur monoxide occurs as a ligand bound to transition metals, typically with hapticity 2.^[19] Examples include OsCl(NO)(PPh₃)₂(S₂O);^[20] [Ir(PPh₂)₂(S₂O)]⁺; and MeCpMn(CO₂)(S₂O).^[19] These complexes are closely related to transition metal sulfur dioxide complexes.

Reactions

On decomposition at room temperature it forms SO₂ via the formation of polysulfur oxides:^[18]

2 S₂O → "S₃" + SO₂

S
₂O reacts with diazoalkanes to form dithiirane 1-oxides.^[21]

References

^ ^a ^b ^c "Disulfur monoxide". NIST. 2008.
^ Hapke, B.; Graham, F. (May 1989). "Spectral properties of condensed phases of disulfur monoxide, polysulfur oxide, and irradiated sulfur". Icarus. 79 (1): 47. Bibcode:1989Icar...79...47H. doi:10.1016/0019-1035(89)90107-3.
^ Clouthier, Dennis J.; Rutherford, Michael L. (1988) [13 May 1988], "Supersonic jet spectroscopy of S₂O", Chemical Physics, 127, Amsterdam: North-Holland: 190, doi:10.1016/0301-0104(88)87117-9
^ Han Huixian; Suo Bingbing; Jiang Zhenyi; Wang Yubin; Wen Zhenyi (2008) [7 Jan 2008]. "The potential energy curves of low-lying electronic states of S₂O". The Journal of Chemical Physics. 128. American Institute of Physics. Fig. 2. doi:10.1063/1.2917236.
^ Navizet, Isabelle; Komiha, Najia; Linguerri, Roberto; Chambaud, Gilberte; Rosmus, Pavel (November 2010). "On the formation of S₂O at low energies: An ab initio study". Chemical Physics Letters. 500 (4–6): 207–210. Bibcode:2010CPL...500..207N. doi:10.1016/j.cplett.2010.10.012.
^ ^a ^b Hallin, K-E. J.; Merer, A. J.; Milton, D. J. (November 1977). "Rotational analysis of bands of the 3400 Å system of disulphur monoxide (S₂O)". Canadian Journal of Physics. 55 (21): 1858–1867. Bibcode:1977CaJPh..55.1858H. doi:10.1139/p77-226.
^ ^a ^b Zhang, Qingguo; Dupré, Patrick; Grzybowski, Bartosz; Vaccaro, Patrick H. (1995). "Laser-induced fluorescence studies of jet-cooled S₂O: Axis-switching and predissociation effects". The Journal of Chemical Physics. 103 (1): 67. Bibcode:1995JChPh.103...67Z. doi:10.1063/1.469623.
^ Cook, Robert L; Winnewisser, Gisbert; Lindsey, D.C (May 1973). "The centrifugal distortion constants of disulfur monoxide". Journal of Molecular Spectroscopy. 46 (2): 276–284. Bibcode:1973JMoSp..46..276C. doi:10.1016/0022-2852(73)90042-8.
^ Meschi, D. J.; Myers, R. J. (1959). "The microwave spectrum, structure, and dipole moment of disulfur monoxide". Journal of Molecular Spectroscopy. 3 (1–6): 405–416. Bibcode:1959JMoSp...3..405M. doi:10.1016/0022-2852(59)90036-0.
^ ^a ^b Steudel, R. (2003). "Sulfur-Rich Oxides S_nO and S_nO₂". In Steudel, R. (ed.). Elemental Sulfur and Sulfur-Rich Compounds II. Berlin/Heidelberg: Springer. ISBN 9783540449515.
^ Meschi, David J.; Myers, Rollie J. (30 July 1956). "Disulfur Monoxide. I. Its Identification as the Major Constituent in Schenk's "Sulfur Monoxide"". Journal of the American Chemical Society. 78 (24): 6220. doi:10.1021/ja01605a002.
^ Satyanarayana, S. R.; Vasudeva Murthy, A. R. (1964). "Reactions with Disulphur monoxide Solutions Obtained by the Reduction of Cupric Oxide by Elemental Sulphur" (PDF). Proceedings of the Indian Academy of Sciences, Section A. 59 (4): 263–267. doi:10.1007/BF03046440. S2CID 91428580. Archived from the original (PDF) on 2014-10-17. Retrieved 2013-11-08.
^ Dodson, R. M.; Srinivasan, V.; Sharma, K. S.; Sauers, Richard F. (July 1972). "Disulfur monoxide. Reaction with dienes". The Journal of Organic Chemistry. 37 (15): 2367–2372. doi:10.1021/jo00980a001. ISSN 0022-3263.
^ Schenk, P. W.; Steudel, R. (1964). "Preparation of Pure Disulfur Monoxide". Angewandte Chemie International Edition in English. 3 (1): 61. doi:10.1002/anie.196400611. ISSN 1521-3773.
^ Nakayama, J.; Aoki, S.; Takayama, J.; Sakamoto, A.; Sugihara, Y.; Ishii, A. (28 July 2004). "Reversible disulfur monoxide (S₂O)-forming retro-Diels–Alder reaction. disproportionation of S₂O to trithio-ozone (S₃) and sulfur dioxide (SO₂) and reactivities of S₂O and S₃". Journal of the American Chemical Society. 126 (29): 9085–9093. doi:10.1021/ja047729i. PMID 15264842.
^ Zolotov, Mikhail Yu.; Fegley, Bruce (9 March 1998). "Volcanic Origin of Disulfur Monoxide (S₂O) on Io" (PDF). Icarus. 133 (2): 293. Bibcode:1998Icar..133..293Z. doi:10.1006/icar.1998.5930. Archived from the original (PDF) on 10 October 2017. Retrieved 2 October 2010.
^ Khan, Ashikur R. (August 1999). Experimental Studies of the Homogenous Conversion of Sulfur Di-Oxide to Sulfur Tri-Oxide via Natural Gas Reburning (Thesis). Ohio University. p. 8. Other sulfur oxides are sulfur monoxide, SO, its dimer, (SO)
_z, and disulfur monoxide, S
₂O. These are too unstable or reactive to appear as products of combustion in the ordinary sense, but they are known to occur as intermediates in appropriate circumstances.
^ ^a ^b Cotton and Wilkinson (1966). Advanced Inorganic Chemistry: A Comprehensive Treatise. p. 540.
^ ^a ^b Urove, Greg A.; Welker, Mark E. (April 1988). "Synthesis of a stable disulfur monoxide precursor and trapping of disulfur monoxide with transition-metal complexes". Organometallics. 7 (4): 1013–1014. doi:10.1021/om00094a037. ISSN 0276-7333.
^ Pandey, Krishna K. (2009-09-17). "Coordination chemistry of thionitrosyl (NS), thiazate (NSO⁻
), disulfidothionitrate (S
₃N⁻
), sulfur monoxide (SO), and disulfur monoxide (S
₂O) ligands". In Lippard, Stephen J. (ed.). Progress in Inorganic Chemistry. Vol. 80. John Wiley & Sons. p. 492. ISBN 978-0-470-16698-7.
^ Ishii, A.; Kawai, T.; Tekura, K.; Oshida, H.; Nakayama, J. (18 May 2001). "A Convenient Method for the Generation of a Disulfur Monoxide Equivalent and Its Reaction with Diazoalkanes to Yield Dithiirane 1-Oxides". Angewandte Chemie International Edition. 40 (10): 1924–1926. doi:10.1002/1521-3773(20010518)40:10<1924::AID-ANIE1924>3.0.CO;2-F. PMID 11385674.

[nist-1] "Disulfur monoxide". NIST. 2008.

[2] Hapke, B.; Graham, F. (May 1989). "Spectral properties of condensed phases of disulfur monoxide, polysulfur oxide, and irradiated sulfur". Icarus. 79 (1): 47. Bibcode:1989Icar...79...47H. doi:10.1016/0019-1035(89)90107-3.

[3] Clouthier, Dennis J.; Rutherford, Michael L. (1988) [13 May 1988], "Supersonic jet spectroscopy of S₂O", Chemical Physics, 127, Amsterdam: North-Holland: 190, doi:10.1016/0301-0104(88)87117-9

[4] Han Huixian; Suo Bingbing; Jiang Zhenyi; Wang Yubin; Wen Zhenyi (2008) [7 Jan 2008]. "The potential energy curves of low-lying electronic states of S₂O". The Journal of Chemical Physics. 128. American Institute of Physics. Fig. 2. doi:10.1063/1.2917236.

[Nav10-5] Navizet, Isabelle; Komiha, Najia; Linguerri, Roberto; Chambaud, Gilberte; Rosmus, Pavel (November 2010). "On the formation of S₂O at low energies: An ab initio study". Chemical Physics Letters. 500 (4–6): 207–210. Bibcode:2010CPL...500..207N. doi:10.1016/j.cplett.2010.10.012.

[Hall77-6] Hallin, K-E. J.; Merer, A. J.; Milton, D. J. (November 1977). "Rotational analysis of bands of the 3400 Å system of disulphur monoxide (S₂O)". Canadian Journal of Physics. 55 (21): 1858–1867. Bibcode:1977CaJPh..55.1858H. doi:10.1139/p77-226.

[Zhang95-7] Zhang, Qingguo; Dupré, Patrick; Grzybowski, Bartosz; Vaccaro, Patrick H. (1995). "Laser-induced fluorescence studies of jet-cooled S₂O: Axis-switching and predissociation effects". The Journal of Chemical Physics. 103 (1): 67. Bibcode:1995JChPh.103...67Z. doi:10.1063/1.469623.

[8] Cook, Robert L; Winnewisser, Gisbert; Lindsey, D.C (May 1973). "The centrifugal distortion constants of disulfur monoxide". Journal of Molecular Spectroscopy. 46 (2): 276–284. Bibcode:1973JMoSp..46..276C. doi:10.1016/0022-2852(73)90042-8.

[9] Meschi, D. J.; Myers, R. J. (1959). "The microwave spectrum, structure, and dipole moment of disulfur monoxide". Journal of Molecular Spectroscopy. 3 (1–6): 405–416. Bibcode:1959JMoSp...3..405M. doi:10.1016/0022-2852(59)90036-0.

[Steudel-10] Steudel, R. (2003). "Sulfur-Rich Oxides S_nO and S_nO₂". In Steudel, R. (ed.). Elemental Sulfur and Sulfur-Rich Compounds II. Berlin/Heidelberg: Springer. ISBN 9783540449515.

[11] Meschi, David J.; Myers, Rollie J. (30 July 1956). "Disulfur Monoxide. I. Its Identification as the Major Constituent in Schenk's "Sulfur Monoxide"". Journal of the American Chemical Society. 78 (24): 6220. doi:10.1021/ja01605a002.

[Satyanarayana64-12] Satyanarayana, S. R.; Vasudeva Murthy, A. R. (1964). "Reactions with Disulphur monoxide Solutions Obtained by the Reduction of Cupric Oxide by Elemental Sulphur" (PDF). Proceedings of the Indian Academy of Sciences, Section A. 59 (4): 263–267. doi:10.1007/BF03046440. S2CID 91428580. Archived from the original (PDF) on 2014-10-17. Retrieved 2013-11-08.

[13] Dodson, R. M.; Srinivasan, V.; Sharma, K. S.; Sauers, Richard F. (July 1972). "Disulfur monoxide. Reaction with dienes". The Journal of Organic Chemistry. 37 (15): 2367–2372. doi:10.1021/jo00980a001. ISSN 0022-3263.

[14] Schenk, P. W.; Steudel, R. (1964). "Preparation of Pure Disulfur Monoxide". Angewandte Chemie International Edition in English. 3 (1): 61. doi:10.1002/anie.196400611. ISSN 1521-3773.

[15] Nakayama, J.; Aoki, S.; Takayama, J.; Sakamoto, A.; Sugihara, Y.; Ishii, A. (28 July 2004). "Reversible disulfur monoxide (S₂O)-forming retro-Diels–Alder reaction. disproportionation of S₂O to trithio-ozone (S₃) and sulfur dioxide (SO₂) and reactivities of S₂O and S₃". Journal of the American Chemical Society. 126 (29): 9085–9093. doi:10.1021/ja047729i. PMID 15264842.

[16] Zolotov, Mikhail Yu.; Fegley, Bruce (9 March 1998). "Volcanic Origin of Disulfur Monoxide (S₂O) on Io" (PDF). Icarus. 133 (2): 293. Bibcode:1998Icar..133..293Z. doi:10.1006/icar.1998.5930. Archived from the original (PDF) on 10 October 2017. Retrieved 2 October 2010.

[17] Khan, Ashikur R. (August 1999). Experimental Studies of the Homogenous Conversion of Sulfur Di-Oxide to Sulfur Tri-Oxide via Natural Gas Reburning (Thesis). Ohio University. p. 8. Other sulfur oxides are sulfur monoxide, SO, its dimer, (SO)
_z, and disulfur monoxide, S
₂O. These are too unstable or reactive to appear as products of combustion in the ordinary sense, but they are known to occur as intermediates in appropriate circumstances.

[candw-18] Cotton and Wilkinson (1966). Advanced Inorganic Chemistry: A Comprehensive Treatise. p. 540.

[:0-19] Urove, Greg A.; Welker, Mark E. (April 1988). "Synthesis of a stable disulfur monoxide precursor and trapping of disulfur monoxide with transition-metal complexes". Organometallics. 7 (4): 1013–1014. doi:10.1021/om00094a037. ISSN 0276-7333.

[20] Pandey, Krishna K. (2009-09-17). "Coordination chemistry of thionitrosyl (NS), thiazate (NSO⁻
), disulfidothionitrate (S
₃N⁻
), sulfur monoxide (SO), and disulfur monoxide (S
₂O) ligands". In Lippard, Stephen J. (ed.). Progress in Inorganic Chemistry. Vol. 80. John Wiley & Sons. p. 492. ISBN 978-0-470-16698-7.

[21] Ishii, A.; Kawai, T.; Tekura, K.; Oshida, H.; Nakayama, J. (18 May 2001). "A Convenient Method for the Generation of a Disulfur Monoxide Equivalent and Its Reaction with Diazoalkanes to Yield Dithiirane 1-Oxides". Angewandte Chemie International Edition. 40 (10): 1924–1926. doi:10.1002/1521-3773(20010518)40:10<1924::AID-ANIE1924>3.0.CO;2-F. PMID 11385674.

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+{{Short description|Chemical compound with sulfur and oxygen}}
+{{Redirect|S<sub>2</sub>O|S2O, a business model for open access|Subscribe to Open}}
 {{chembox
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 | MainHazards = toxic
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-| SPhrases =
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-'''Disulfur monoxide''' or '''sulfur suboxide''' is an [[inorganic compound]] with formula S<sub>2</sub>O.  It is one of the [[lower sulfur oxides]]. It is a colourless gas and condenses to give a pale coloured solid that is unstable at room temperature.<ref name=Steudel>{{cite book|first=R.|last=Steudel|contribution=Sulfur-Rich Oxides S<sub>''n''</sub>O and S<sub>''n''</sub>O<sub>2</sub>|title=Elemental Sulfur and Sulfur-Rich Compounds II|editor-last=Steudel|editor-first=R.|date=2003|publisher=Springer|location=Berlin/Heidelberg|isbn=9783540449515}}</ref>  It is a bent molecule with an S&minus;S&minus;O angle of 117.88°, S&minus;S bond length of 188.4&nbsp;pm, and S&minus;O bond length of 146.5&nbsp;pm.<ref>{{cite journal
+'''Disulfur monoxide''' or '''sulfur suboxide''' is an [[inorganic compound]] with the formula S<sub>2</sub>O, one of the [[lower sulfur oxides]]. It is a colourless gas and condenses to give a roughly dark red coloured solid that is unstable at room temperature.
-| last1 =Meschi | first1 =D. J. | last2=Myers|first2= R. J.| year = 1959| title = The microwave spectrum, structure, and dipole moment of disulfur monoxide| journal = Journal of Molecular Spectroscopy| volume = 3| issue =1–6 | pages =405–416 | doi = 10.1016/0022-2852(59)90036-0|bibcode = 1959JMoSp...3..405M }}</ref>
+{{Chem|S|2|O}} occurs rarely in natural atmospheres, but can be made by a variety of laboratory procedures.  For this reason, its spectroscopic signature is very well understood.
+== Structure and spectrum ==
+Like [[sulfur dioxide]] (and, indeed, most molecules) but unlike [[sulfur monoxide]], [[disulfur]], or [[dioxygen]], the ground state of disulfur monoxide is a singlet.<ref>{{cite|doi=10.1016/0301-0104(88)87117-9|p=190|journal=Chemical Physics|volume=127|year=1988|publisher=North-Holland|location=Amsterdam|title=Supersonic jet spectroscopy of S<sub>2</sub>O|first1=Dennis&nbsp;J.|last1=Clouthier|first2=Michael&nbsp;L.|last2=Rutherford|orig-date=13 May 1988}}</ref><ref>{{cite journal|doi=10.1063/1.2917236|journal=The Journal of Chemical Physics|volume=128|at=Fig.&nbsp;2.|year=2008|title=The potential energy curves of low-lying electronic states of S<sub>2</sub>O|author1=Han Huixian|author2=Suo Bingbing|author3=Jiang Zhenyi|author4=Wang Yubin|author5=Wen Zhenyi|orig-date=7 Jan 2008|publisher=American Institute of Physics}}</ref>
+Condensed solid S<sub>2</sub>O [[absorption bands|absorbs]] at {{Val|420|u=nm}} (roughly [[Indigo (color)|indigo]]) and {{Val|530|u=nm}} (roughly [[Lime (color)|lime]]). These bands have been assigned to decomposition products [[Trisulfur|S<sub>3</sub>]] and [[Tetrasulfur|S<sub>4</sub>]].<ref name=Nav10>{{cite journal|last1=Navizet|first1=Isabelle|last2=Komiha|first2=Najia|last3=Linguerri|first3=Roberto|last4=Chambaud|first4=Gilberte|last5=Rosmus|first5=Pavel|title=On the formation of S<sub>2</sub>O at low energies: An ab initio study|journal=Chemical Physics Letters|date=November 2010|volume=500|issue=4–6|pages=207–210|doi=10.1016/j.cplett.2010.10.012|bibcode = 2010CPL...500..207N }}</ref>
-It also arises via thermal decomposition of [[sulfur dioxide]] in a [[glow discharge]].<ref name=candw/>
+In the ultraviolet, S<sub>2</sub>O has absorption band systems in the ranges 250–340&nbsp;nm and 190–240&nbsp;nm. There are bands at 323.5 and 327.8&nbsp;nm.<ref name="Hall77">{{cite journal|last1=Hallin|first1=K-E. J.|last2=Merer|first2=A. J.|last3=Milton|first3=D. J.|title=Rotational analysis of bands of the 3400&nbsp;Å system of disulphur monoxide (S<sub>2</sub>O)|journal=Canadian Journal of Physics|date=November 1977|volume=55|issue=21|pages=1858–1867|doi=10.1139/p77-226|bibcode = 1977CaJPh..55.1858H }}</ref> The band in the 315–340&nbsp;nm range is due to the {{nowrap|C<sup>1</sup>''A''′–X<sup>1</sup>''A''′ (π* ← π)}} transition.<ref name="Zhang95">{{cite journal|last1=Zhang|first1=Qingguo|last2=Dupré|first2=Patrick|last3=Grzybowski|first3=Bartosz|last4=Vaccaro|first4=Patrick H.|title=Laser-induced fluorescence studies of jet-cooled S<sub>2</sub>O: Axis-switching and predissociation effects|journal=The Journal of Chemical Physics|date=1995|volume=103|issue=1|pages=67|doi=10.1063/1.469623|bibcode = 1995JChPh.103...67Z }}</ref>
-Disulfur monoxide forms a yellow solution in [[carbon tetrachloride]].<ref name="Satyanarayana64"/>  The solid can be obtained at [[liquid nitrogen]] temperatures, often appearing dark-colored owing to impurities. On decomposition at room temperature it forms [[sulfur dioxide|SO<sub>2</sub>]] via the formation of polysulfur oxides.<ref name=candw>{{cite book|title=Advanced Inorganic Chemistry: A Comprehensive Treatise|author=Cotton and Wilkinson|year=1966|page=540}}</ref>
+Gaseous disulfur monoxide does not absorb light in the [[visible spectrum]].
-==Spectroscopy==
-Condensed solid S<sub>2</sub>O [[absorption bands|absorbs]] at 420 and 530&nbsp;nm. These bands have been assigned to decomposition products [[Trisulfur|S<sub>3</sub>]] and [[Tetrasulfur|S<sub>4</sub>]].<ref name=Nav10>{{cite journal|last1=Navizet|first1=Isabelle|last2=Komiha|first2=Najia|last3=Linguerri|first3=Roberto|last4=Chambaud|first4=Gilberte|last5=Rosmus|first5=Pavel|title=On the formation of S<sub>2</sub>O at low energies: An ab initio study|journal=Chemical Physics Letters|date=November 2010|volume=500|issue=4–6|pages=207–210|doi=10.1016/j.cplett.2010.10.012|bibcode = 2010CPL...500..207N }}</ref>
-The [[Microwave spectroscopy|microwave spectrum]] of S<sub>2</sub>O has the following rotational parameters: ''A''&nbsp;= 41915.44&nbsp;MHz, ''B''&nbsp;= 5059.07&nbsp;MHz, and ''C''&nbsp;= 4507.19&nbsp;MHz.<ref>{{cite journal|last1=Cook|first1=Robert L|last2=Winnewisser|first2=Gisbert|last3=Lindsey|first3=D.C|title=The centrifugal distortion constants of disulfur monoxide|journal=Journal of Molecular Spectroscopy|date=May 1973|volume=46|issue=2|pages=276–284|doi=10.1016/0022-2852(73)90042-8|bibcode = 1973JMoSp..46..276C }}</ref>
+The [[Microwave spectroscopy|microwave spectrum]] of S<sub>2</sub>O has the following rotational parameters: ''A''&nbsp;= 41915.44&nbsp;MHz, ''B''&nbsp;= 5059.07&nbsp;MHz, and ''C''&nbsp;= 4507.19&nbsp;MHz.<ref>{{cite journal|last1=Cook|first1=Robert L|last2=Winnewisser|first2=Gisbert|last3=Lindsey|first3=D.C|date=May 1973|title=The centrifugal distortion constants of disulfur monoxide|journal=Journal of Molecular Spectroscopy|volume=46|issue=2|pages=276–284|bibcode=1973JMoSp..46..276C|doi=10.1016/0022-2852(73)90042-8}}</ref>  Moreover, the microwave spectrum suggests the S&minus;S&minus;O angle is 117.88° with S&minus;S and S&minus;O bond lengths of 188.4 and 146.5&nbsp;pm, respectively.<ref>{{cite journal|last1=Meschi|first1=D. J.|last2=Myers|first2=R. J.|year=1959|title=The microwave spectrum, structure, and dipole moment of disulfur monoxide|journal=Journal of Molecular Spectroscopy|volume=3|issue=1–6|pages=405–416|bibcode=1959JMoSp...3..405M|doi=10.1016/0022-2852(59)90036-0}}</ref>  In the 327.8&nbsp;nm excited state, the central angle tightens to 109°.<ref name="Hall77" />
+The [[harmonic frequency]] for S&minus;S stretching is 415.2&nbsp;cm<sup>−1</sup>.<ref name=Zhang95/>
-In the ultraviolet S<sub>2</sub>O has absorption band systems in the ranges 250–340&nbsp;nm and 190–240&nbsp;nm. There are bands at 323.5 and 327.8&nbsp;nm.<ref name=Hall77>{{cite journal|last1=Hallin|first1=K-E. J.|last2=Merer|first2=A. J.|last3=Milton|first3=D. J.|title=Rotational analysis of bands of the 3400&nbsp;Å system of disulphur monoxide (S<sub>2</sub>O)|journal=Canadian Journal of Physics|date=November 1977|volume=55|issue=21|pages=1858–1867|doi=10.1139/p77-226|bibcode = 1977CaJPh..55.1858H }}</ref> The band in the 315–340&nbsp;nm range is due to the {{nowrap|C<sup>1</sup>''A''′–X<sup>1</sup>''A''′ (π* ← π)}} transition.<ref name=Zhang95>{{cite journal|last1=Zhang|first1=Qingguo|last2=Dupré|first2=Patrick|last3=Grzybowski|first3=Bartosz|last4=Vaccaro|first4=Patrick H.|title=Laser-induced fluorescence studies of jet-cooled S<sub>2</sub>O: Axis-switching and predissociation effects|journal=The Journal of Chemical Physics|date=1995|volume=103|issue=1|pages=67|doi=10.1063/1.469623|bibcode = 1995JChPh.103...67Z }}</ref>
-The bond angle S&minus;S&minus;O is 109°.<ref name=Hall77/> The [[harmonic frequency]] for S&minus;S stretching is 415.2&nbsp;cm<sup>−1</sup>.<ref name=Zhang95/>
 ==Synthesis==
 ===Historical===
-Disulfur monoxide was discovered by Peter W. Schenk in 1933.<ref name=Steudel/> 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 it decomposed near {{cvt|30|mmHg|kPa|0}}. Schenk assigned the formula as SO and called it [[sulfur monoxide]].   In 1956, D. J. Meschi and R. J. Myers established the formula as S<sub>2</sub>O.<ref>{{cite journal|journal=Journal of the American Chemical Society|title=Disulfur Monoxide. I. Its Identification as the Major Constituent in Schenk's "Sulfur Monoxide"|first1=David J.|last1=Meschi|first2=Rollie J.|last2=Myers|date=30 July 1956|volume=78|issue=24|page=6220|doi=10.1021/ja01605a002}}</ref>
+Disulfur monoxide was discovered by Peter W. Schenk in 1933<ref name="Steudel">{{cite book|last=Steudel|first=R.|title=Elemental Sulfur and Sulfur-Rich Compounds II|date=2003|publisher=Springer|isbn=9783540449515|editor-last=Steudel|editor-first=R.|location=Berlin/Heidelberg|contribution=Sulfur-Rich Oxides S<sub>''n''</sub>O and S<sub>''n''</sub>O<sub>2</sub>}}</ref> 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 it decomposed near {{cvt|30|mmHg|kPa|0}}. Schenk assigned the formula as SO and called it [[sulfur monoxide]].   In 1956, D. J. Meschi and R. J. Myers established the formula as S<sub>2</sub>O.<ref>{{cite journal|journal=Journal of the American Chemical Society|title=Disulfur Monoxide. I. Its Identification as the Major Constituent in Schenk's "Sulfur Monoxide"|first1=David J.|last1=Meschi|first2=Rollie J.|last2=Myers|date=30 July 1956|volume=78|issue=24|page=6220|doi=10.1021/ja01605a002}}</ref>
 ===Preparation===
+Oxidizing [[sulfur]] with [[copper(II) oxide]]:<ref name="Satyanarayana64">{{cite journal|last1=Satyanarayana|first1=S. R.|last2=Vasudeva Murthy|first2=A. R.|year=1964|title=Reactions with Disulphur monoxide Solutions Obtained by the Reduction of Cupric Oxide by Elemental Sulphur|url=http://eprints.iisc.ernet.in/28079/1/32.pdf|journal=Proceedings of the Indian Academy of Sciences, Section A|volume=59|issue=4|pages=263–267|doi=10.1007/BF03046440|s2cid=91428580|access-date=2013-11-08|archive-date=2014-10-17|archive-url=https://web.archive.org/web/20141017050607/http://eprints.iisc.ernet.in/28079/1/32.pdf|url-status=dead}}</ref><ref>{{Cite journal|last1=Dodson|first1=R. M.|last2=Srinivasan|first2=V.|last3=Sharma|first3=K. S.|last4=Sauers|first4=Richard F.|date=July 1972|title=Disulfur monoxide. Reaction with dienes|url=https://pubs.acs.org/doi/pdf/10.1021/jo00980a001|journal=The Journal of Organic Chemistry|volume=37|issue=15|pages=2367–2372|doi=10.1021/jo00980a001|issn=0022-3263}}</ref>
-The reaction of [[thionyl chloride]] with [[silver(I) sulfide]]:
+:3&nbsp;S<sub>8</sub> + 12&nbsp;CuO → 12&nbsp;CuS +  4&nbsp;S<sub>2</sub>O + 4&nbsp;SO<sub>2</sub>
+A relatively pure generator is the reaction of [[thionyl chloride]] with [[silver(I) sulfide]]:<ref>{{Cite journal|last1=Schenk|first1=P. W.|last2=Steudel|first2=R.|date=1964|title=Preparation of Pure Disulfur Monoxide|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.196400611|journal=Angewandte Chemie International Edition in English|language=en|volume=3|issue=1|pages=61|doi=10.1002/anie.196400611|issn=1521-3773}}</ref>
 :SOCl<sub>2</sub> + Ag<sub>2</sub>S → 2&nbsp;AgCl + S<sub>2</sub>O
-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 S<sub>2</sub>O.<ref>{{cite journal|title=Reversible disulfur monoxide (S<sub>2</sub>O)-forming retro-Diels–Alder reaction. disproportionation of S<sub>2</sub>O to trithio-ozone (S<sub>3</sub>) and sulfur dioxide (SO<sub>2</sub>) and reactivities of S<sub>2</sub>O and S<sub>3</sub>|first6=A.|last6=Ishii|first5=Y.|last5=Sugihara|first4=A.|last4=Sakamoto|first3=J.|last3=Takayama|first2=S.|last2=Aoki|last1=Nakayama|first1=J.|journal=Journal of the American Chemical Society|date=28 July 2004|volume=126|issue=29|pmid=15264842|doi=10.1021/ja047729i|pages=9085–9093}}</ref>  It reacts with diazoalkanes to form dithiirane 1-oxides.<ref>{{cite journal|title=A Convenient Method for the Generation of a Disulfur Monoxide Equivalent and Its Reaction with Diazoalkanes to Yield Dithiirane 1-Oxides|first5=J.|last5=Nakayama|first4=H.|last4=Oshida|first3=K.|last3=Tekura|first2=T.|last2=Kawai|first1=A.|last1=Ishii|journal=Angewandte Chemie International Edition|date=18 May 2001|pages=1924–1926|volume=40|issue=10|pmid=11385674|doi=10.1002/1521-3773(20010518)40:10<1924::AID-ANIE1924>3.0.CO;2-F}}</ref>
+Also 5,6-di-''tert''-butyl-2,3,7-trithiabicyclo[2.2.1]hept-5-ene 2-''endo''-7-''endo''-dioxide decomposes upon heating with release of S<sub>2</sub>O:<ref>{{cite journal|title=Reversible disulfur monoxide (S<sub>2</sub>O)-forming retro-Diels–Alder reaction. disproportionation of S<sub>2</sub>O to trithio-ozone (S<sub>3</sub>) and sulfur dioxide (SO<sub>2</sub>) and reactivities of S<sub>2</sub>O and S<sub>3</sub>|first6=A.|last6=Ishii|first5=Y.|last5=Sugihara|first4=A.|last4=Sakamoto|first3=J.|last3=Takayama|first2=S.|last2=Aoki|last1=Nakayama|first1=J.|journal=Journal of the American Chemical Society|date=28 July 2004|volume=126|issue=29|pmid=15264842|doi=10.1021/ja047729i|pages=9085–9093}}</ref>  <blockquote>[[File:S2Ogeneration.svg]]</blockquote>
-[[File:S2Ogeneration.svg]]
 ==Occurrence==
 ===Volcanism===
-S<sub>2</sub>O can be found coming from volcanoes on [[Io (moon)|Io]]. It can form between 1% and 6% when hot 100-bar S<sub>2</sub> and SO<sub>2</sub> gas erupts from volcanoes.  It is believed that [[Pele (volcano)|Pele]] on Io is surrounded by solid S<sub>2</sub>O.<ref>{{cite journal|url=http://zolotov.faculty.asu.edu/publ/Io-S2O-1998.pdf|first1=Mikhail Yu.|last1=Zolotov|first2=Bruce|last2=Fegley|title=Volcanic Origin of Disulfur Monoxide (S<sub>2</sub>O) on Io|journal=Icarus|volume=133|page=293|date=9 March 1998|doi=10.1006/icar.1998.5930|issue=2 |bibcode = 1998Icar..133..293Z }}</ref>
+Volcanoes on [[Io (moon)|Io]] produce substantial quantities of {{Chem|S|2|O}}.  It can form between 1% and 6% when hot 100-bar S<sub>2</sub> and SO<sub>2</sub> gas erupts from volcanoes.  It is believed that [[Pele (volcano)|Pele]] on Io is surrounded by solid S<sub>2</sub>O.<ref>{{cite journal|url=http://zolotov.faculty.asu.edu/publ/Io-S2O-1998.pdf|first1=Mikhail Yu.|last1=Zolotov|first2=Bruce|last2=Fegley|title=Volcanic Origin of Disulfur Monoxide (S<sub>2</sub>O) on Io|journal=Icarus|volume=133|page=293|date=9 March 1998|doi=10.1006/icar.1998.5930|issue=2|bibcode=1998Icar..133..293Z|access-date=2 October 2010|archive-date=10 October 2017|archive-url=https://web.archive.org/web/20171010200253/http://zolotov.faculty.asu.edu/publ/Io-S2O-1998.pdf|url-status=dead}}</ref>
-===Combustion===
-It can be formed by many methods, including combustion of sulfur vapour in a deficiency of oxygen. It arises by oxidizing [[sulfur]] with [[copper(II) oxide]]:<ref name="Satyanarayana64">{{cite journal|last=Satyanarayana|first=S. R.|first2=A. R.|last2=Vasudeva Murthy|year=1964|title=Reactions with Disulphur monoxide Solutions Obtained by the Reduction of Cupric Oxide by Elemental Sulphur|journal=Proceedings of the Indian Academy of Sciences, Section A|volume=59|issue=4|url=http://eprints.iisc.ernet.in/28079/1/32.pdf}}</ref>
+===Terran atmosphere===
-:3&nbsp;S<sub>8</sub> + 12&nbsp;CuO → 12&nbsp;CuS +  4&nbsp;S<sub>2</sub>O + 4&nbsp;SO<sub>2</sub>
+Disulfur monoxide is too unstable to survive at standard conditions,<ref name="Steudel" /> but transient sources include [[incomplete combustion]] of sulfur vapor<ref>{{Cite thesis|last=Khan|first=Ashikur R.|title=Experimental Studies of the Homogenous Conversion of Sulfur Di-Oxide to Sulfur Tri-Oxide via Natural Gas Reburning|date=August 1999|publisher=Ohio University|url=https://etd.ohiolink.edu/apexprod/rws_etd/send_file/send?accession=ohiou1175798586|page=8|quote=Other sulfur oxides are sulfur monoxide, {{chem|S|O}}, its dimer, {{chem|(SO)|z}}, and disulfur monoxide, {{chem|S|2|O}}. These are too unstable or reactive to appear as products of combustion in the ordinary sense, but they are known to occur as intermediates in appropriate circumstances.}}</ref> and thermal decomposition of [[sulfur dioxide]] in a [[glow discharge]].<ref name="candw" />
 ===As a ligand ===
+Disulfur monoxide occurs as a [[ligand]] bound to [[transition metal]]s, typically with [[hapticity]] 2.<ref name=":0">{{Cite journal|last1=Urove|first1=Greg A.|last2=Welker|first2=Mark E.|date=April 1988|title=Synthesis of a stable disulfur monoxide precursor and trapping of disulfur monoxide with transition-metal complexes|url=https://pubs.acs.org/doi/pdf/10.1021/om00094a037|journal=Organometallics|volume=7|issue=4|pages=1013–1014|doi=10.1021/om00094a037|issn=0276-7333}}</ref> Examples include {{Chem2|OsCl(NO)(PPh3)2(S2O)}};<ref>{{Cite book|last=Pandey|first=Krishna&nbsp;K.|chapter-url=https://books.google.com/books?id=-mtAYfs9B3YC&pg=PA492|title=Progress in Inorganic Chemistry|date=2009-09-17|publisher=John Wiley & Sons|isbn=978-0-470-16698-7|editor-last=Lippard|editor-first=Stephen&nbsp;J.|volume=80|pages=492|language=en|chapter=Coordination chemistry of thionitrosyl ({{chem|N|S}}), thiazate ({{chem|N|S|O|-}}), disulfidothionitrate ({{chem|S|3|N|-}}), sulfur monoxide ({{chem|S|O}}), and disulfur monoxide ({{chem|S|2|O}}) ligands}}</ref> {{Chem2|[Ir(PPh2)2(S2O)]+}}; and {{Chem2|MeCpMn(CO2)(S2O)}}.<ref name=":0" />  These complexes are closely related to [[transition metal sulfur dioxide complex]]es.
-Disulfur monoxide is a [[ligand]] bound to [[transition metal]]s. These are formed by oxidation peroxide oxidation of a disulfur ligand. Excessive oxygen can yield a dioxygendisulfur ligand, which can be reduced in turn with [[triphenylphosphine]]. Examples are: [Ir(dppe)<sub>2</sub>S<sub>2</sub>O]<sup>+</sup>, OsCl(NO)(PPh<sub>3</sub>)<sub>2</sub>S<sub>2</sub>O, NbCl(''η''-C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>S<sub>2</sub>O, Mn(CO)<sub>2</sub>(''η''-C<sub>5</sub>Me<sub>5</sub>)S<sub>2</sub>O, Re(CO)<sub>2</sub>(''η''-C<sub>5</sub>Me<sub>5</sub>)S<sub>2</sub>O, Re(CO)<sub>2</sub>(''η''-C<sub>5</sub>H<sub>5</sub>)S<sub>2</sub>O.<ref name=aioc>{{cite book|url=https://books.google.com/books?id=SMsrNhK_5y4C|page=168|title=Advances in Organometallic Chemistry|volume=36|first=F. G. A.|last=Stone|isbn=978-0-12-031136-1|date=7 March 1994}}</ref>
-The molybdenum compound Mo(CO)<sub>2</sub>(S<sub>2</sub>CNEt<sub>2</sub>)<sub>2</sub> reacts with elemental sulfur and air to form a compound Mo<sub>2</sub>(S<sub>2</sub>O)<sub>2</sub>(S<sub>2</sub>CNEt<sub>2</sub>)<sub>4</sub>.<ref name=aioc/>   Another way to form these complexes is to combine [[sulfonyliminooxosulfurane|sulfonyliminooxo-''λ''<sup>4</sup>-sulfurane]] (OSNSO<sub>2</sub>·R) complexes with [[hydrogen sulfide]].<ref name=aioc/>  Complexes formed in this way are: IrCl(CO)(PPh<sub>3</sub>)<sub>2</sub>S<sub>2</sub>O; Mn(CO)<sub>2</sub>(''η''-C<sub>5</sub>H<sub>5</sub>)S<sub>2</sub>O.  With hydrosulfide and a base followed by oxygen, OsCl(NO)(PPh<sub>3</sub>)<sub>2</sub>S<sub>2</sub>O can be made.<ref name=aioc/>
 ==Reactions==
+On decomposition at room temperature it forms [[sulfur dioxide|SO<sub>2</sub>]] via the formation of polysulfur oxides:<ref name=candw>{{cite book|title=Advanced Inorganic Chemistry: A Comprehensive Treatise|author=Cotton and Wilkinson|year=1966|page=540}}</ref>
-S<sub>2</sub>O disproportionates to [[trisulfur]] and [[sulfur dioxide]]:
-:2&nbsp;S<sub>2</sub>O → S<sub>3</sub> + SO<sub>2</sub>
+:2&nbsp;S<sub>2</sub>O → "S<sub>3</sub>"  +  SO<sub>2</sub>
+{{Chem|S|2|O}} reacts with [[diazoalkane]]s to form [[dithiirane 1-oxides]].<ref>{{cite journal|last1=Ishii|first1=A.|last2=Kawai|first2=T.|last3=Tekura|first3=K.|last4=Oshida|first4=H.|last5=Nakayama|first5=J.|date=18 May 2001|title=A Convenient Method for the Generation of a Disulfur Monoxide Equivalent and Its Reaction with Diazoalkanes to Yield Dithiirane 1-Oxides|journal=Angewandte Chemie International Edition|volume=40|issue=10|pages=1924–1926|doi=10.1002/1521-3773(20010518)40:10<1924::AID-ANIE1924>3.0.CO;2-F|pmid=11385674}}</ref>
 ==Further reading==
-*Possible biological occurrence: {{cite journal|last1=Iverson|first1=W. P.|title=Disulfur monoxide: production by ''Desulfovibrio''|journal=Science|date=26 May 1967|volume=156|pages=1112–1114|issue=3778|pmid= 6024190|doi=10.1126/science.156.3778.1112|bibcode = 1967Sci...156.1112I |url=http://www.dtic.mil/get-tr-doc/pdf?AD=AD0813804}}
+*Possible biological occurrence: {{cite journal|last1=Iverson|first1=W. P.|title=Disulfur monoxide: production by ''Desulfovibrio''|journal=Science|date=26 May 1967|volume=156|pages=1112–1114|issue=3778|pmid= 6024190|doi=10.1126/science.156.3778.1112|bibcode = 1967Sci...156.1112I |s2cid=3058359|url=http://www.dtic.mil/get-tr-doc/pdf?AD=AD0813804|archive-url=https://web.archive.org/web/20170926033814/http://www.dtic.mil/get-tr-doc/pdf?AD=AD0813804|url-status=dead|archive-date=September 26, 2017}}
 *Cyclic disulfur monoxide: {{cite journal|last1=Lo|first1=Wen-Jui|last2=Wu|first2=Yu-Jong|author-link3=Yuan-Pern Lee|last3=Lee|first3=Yuan-Pern|title=Ultraviolet Absorption Spectrum of Cyclic S<sub>2</sub>O in Solid Ar|journal=The Journal of Physical Chemistry A|date=September 2003|volume=107|issue=36|pages=6944–6947|doi=10.1021/jp034563j|bibcode=2003JPCA..107.6944L}}
 *Discovery of S<sub>2</sub>O: {{cite journal|last1=Schenk|first1=Peter W.|title=Über das Schwefelmonoxyd|trans-title=On sulfur monoxide|journal=Zeitschrift für Anorganische und Allgemeine Chemie|date=18 March 1933|volume=211|issue=1–2|pages=150–160|doi=10.1002/zaac.19332110117|language=de}}