Disulfur dinitride

Disulfur dinitride
Preferred IUPAC name dinitrogen disulfide
Systematic name 1λ4,3,2,4-Dithiadiazete
Other names Cyclic sulfur(II,IV) nitride
Identifiers
CAS number	25474-92-4
PubChem	141213 Y
ChemSpider	124561 Y
Jmol-3D images	Image 1
SMILES S1N=S=N1
InChI InChI=1S/N2S2/c1-3-2-4-1 Key: HGFWWXXKPBDJAH-UHFFFAOYSA-N
Properties
Molecular formula	S2N2
Molar mass	92.1444 g/mol
Appearance	colourless crystals
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Disulfur dinitride is the chemical compound S₂N₂ with a cyclic square planar structure.

Preparation and reactions

Passing gaseous S₄N₄ over silver metal wool at 250-300°C at low pressure (1mm Hg) 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 S₄N₄ into the four-membered ring S₂N₂,^[1]

S₄N₄ + 8 Ag → 4 Ag₂S + 2 N₂

S₄N₄ → 2S₂N₂

An alternative uses the less explosive S₄N₃Cl.^[2]
S₂N₂ decomposes explosively above 30°, and is shock sensitive.^[1] It readily sublimes, insoluble in water, soluble in diethyl ether and traces of water cause it to polymerise into S₄N₄.^[2] In the solid state it spontaneously polymerizes forming (SN)x.^[1] It forms adducts with Lewis acids via a nitrogen atom, e.g. S₂N₂.BCl₃, S₂N₂.2AlCl₃, S₂N₂.SbCl₅, S₂N₂.2SbCl₅.^[2][3]

Structure and bonding

The S₂N₂ molecule is virtually square and planar. The S-N bond lengths are 165.1pm and 165.7pm and the bond angles are very close to 90.^[1] The S₂N₂ molecule is isoelectronic with the S₄²⁺ and has 6π electrons.^[2] The bonding has been investigated using a spin-coupled valence bond method ^[4] 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

• Tetrasulfur tetranitride
• Polythiazyl

References

1. ^ ^{a b c d} Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419. 
2. ^ ^{a b c d} Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5
3. ^ The Crystal and Molecular Structure of S₂N₂(SbCl₅)₂ Patton R. L., Raymond K.N.,Inorganic Chemistry 8,11, 2426 (1969) doi:10.1021/ic50081a035
4. ^ ’’The Extraordinary Electronic Structure of N₂S₂’’ J. Gerratt, S. J. McNicholas, P. B. Karadakov, M. Sironi, M. Raimondi, D. L. Cooper, J. Am. Chem. Soc., 118 (27), 6472 -6476, 1996. doi:10.1021/ja953994f