Disulfur dinitride
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| Names | |
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| Preferred IUPAC name
Disulfur dinitride | |
| Systematic IUPAC name
1λ4,3,2,4-Dithiadiazete | |
| Other names
Cyclic sulfur(II,IV) nitride
1,3-dithia-2,4-diazacyclobutan-2,4-diyl | |
| Identifiers | |
3D model (JSmol)
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| ChEBI | |
| ChemSpider | |
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| S2N2 | |
| Molar mass | 92.1444 g/mol |
| Appearance | colourless crystals |
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 dinitride is the chemical compound with the formula S2N2.
Preparation and reactions
Passing gaseous S4N4 over silver metal wool at 250–300 °C at low pressure (1 mmHg) yields cyclic S2N2. The silver reacts with the sulfur produced by the thermal decomposition of the S4N4 to form Ag2S, and the resulting Ag2S catalyzes the conversion of the remaining S4N4 into the four-membered ring S2N2,[1]
- S4N4 + 8 Ag → 4 Ag2S + 2 N2
- S4N4 → 2 S2N2
An alternative uses the less explosive S4N3Cl.[2]
S2N2 decomposes explosively above 30°C, and is shock sensitive.[1] It readily sublimes, and is soluble in diethyl ether. Traces of water[2] or other nucleophiles cause it to polymerize into S4N4.[3] In the solid state it spontaneously polymerizes forming (SN)n,[1] catalyzed by radical impurities.[3] It forms adducts with Lewis acids via a nitrogen atom, e.g. S2N2·BCl3, S2N2·2AlCl3, S2N2·SbCl5, S2N2·2SbCl5.[2][4]
Structure and bonding
The S2N2 molecule is a four-membered ring, with alternating S and N atoms. The molecule is almost square and planar. The S–N bond lengths are 165.1 pm and 165.7 pm and the bond angles are very close to 90°.[1]
The S2N2 molecule is isoelectronic with the cyclic S2+4 dication,[2] but the oft-quoted description of S2N2 bearing 6 π electrons is inaccurate. According to spin-coupled valence bond analysis, the molecule is instead better interpreted as two conjoined sulfur diimides: each sulfur atom bears a single +1 formal charge and one lone pair and each nitrogen atom a single -1 formal charge and two lone pairs. The remaining two electrons, each located on sulfur, are coupled across the ring as a singlet diradical. Loosely, the HOMO and LUMO of S2N2 are each nonbonding orbitals corresponding to these two electrons.[5]
See also
- Sulfur nitride
- Tetrasulfur tetranitride
- Polythiazyl
- Square planar molecular geometry
References
- ^ a b c d Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.
- ^ a b c d Wiberg, E.; Holleman, A. F. (2001). Inorganic Chemistry. Elsevier. ISBN 0-12-352651-5.
- ^ a b Oakley, Richard T. "Cyclic and heterocyclic thiazines". In Lippard, Stephen L. (ed.). Progress in Inorganic Chemistry. Vol. 36. NY, NY: Interscience. p. 304. ISBN 0-471-61144-1. LCCN 59-13035.
- ^ Patton R. L.; Raymond, K. N. (1969). "The Crystal and Molecular Structure of S2N2(SbCl5)2". Inorganic Chemistry. 8 (11): 2426–2431. doi:10.1021/ic50081a035.
- ^ Gerratt, J.; McNicholas, S. J.; Karadakov, P. B.; Sironi, M.; Raimondi, M.; Cooper, D. L. (1996). "The Extraordinary Electronic Structure of N2S2". Journal of the American Chemical Society. 118 (27): 6472–6476. Bibcode:1996JAChS.118.6472G. doi:10.1021/ja953994f.