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Disulfur dinitride

Names
Preferred IUPAC name Disulfur dinitride
Systematic IUPAC name 1λ,3,2,4-Dithiadiazete
Other names Cyclic sulfur(II,IV) nitride 1,3-dithia-2,4-diazacyclobutan-2,4-diyl
Identifiers
CAS Number	25474-92-4
3D model (JSmol)	Interactive image
ChEBI	CHEBI:37756
ChemSpider	124561
PubChem CID	141213
CompTox Dashboard (EPA)	DTXSID401027576
InChI InChI=1S/N2S2/c1-3-2-4-1Key: HGFWWXXKPBDJAH-UHFFFAOYSA-N
SMILES S1N=S=N1
Properties
Chemical formula	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 , 100 kPa). Infobox references

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,

S₄N₄ + 8 Ag → 4 Ag₂S + 2 N₂

S₄N₄ → 2 S₂N₂

An alternative uses the less explosive S₄N₃Cl.

S₂N₂ decomposes explosively above 30°C, and is shock sensitive. It readily sublimes, and is soluble in diethyl ether. Traces of water cause it to polymerize into S₄N₄. In the solid state it spontaneously polymerizes forming (SN)_n. It forms adducts with Lewis acids via a nitrogen atom, e.g. S₂N₂·BCl₃, S₂N₂·2AlCl₃, S₂N₂·SbCl₅, S₂N₂·2SbCl₅.

Structure and bonding

The S₂N₂ molecule is a four-membered ring, with alternating S and N atoms. The S₂N₂ molecule is a resonance hybrid of many contributing structures. In one of those structures, one S atom has valence 4 and the other S atom has valence 2, and both N atoms has valence 3. In the other structure both S atoms have valence 2 and both N atoms has valence 3, and one of the S atoms has a charge of +1, and one of the N atoms has a charge of −1. 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°. The S₂N₂ molecule is isoelectronic with the cyclic S2+4 dication and has 6π electrons. The bonding has been investigated using a spin-coupled valence bond method and is described as having four framework sigma bonds, with the N atoms bearing a high negative charge and the S atoms a corresponding positive charge. Two π electrons from the sulfur atoms are coupled across the ring making the molecule overall a singlet diradical.

See also

• Sulfur nitride
• Tetrasulfur tetranitride
• Polythiazyl
• Square planar molecular geometry

References

1. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
2. ^ Wiberg, E.; Holleman, A. F. (2001). Inorganic Chemistry. Elsevier. ISBN 0-12-352651-5.
3. 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.
4. 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. doi:10.1021/ja953994f.

• Nitrides
• Four-membered rings
• Sulfur–nitrogen compounds
• Explosive chemicals