Disulfur dinitride

Passing gaseous tetrasulfur tetranitride over silver metal wool at 250–300 °C at low pressure (1 mmHg) yields cyclic {{chem2|S2N2}}. The silver reacts with the sulfur produced by the thermal decomposition of the {{chem2|S4N4}} to form silver sulfide, and the resulting {{chem2|Ag2S}} catalyzes the conversion of the remaining {{chem2|S4N4}} into the four-membered ring {{chem2|S2N2}},{{Greenwood&Earnshaw}}

:{{chem2|S4N4 + 8 Ag → 4 Ag2S + 2 N2}}

:{{chem2|S4N4 → 2 S2N2}}

An alternative uses the less explosive {{chem2|S4N3Cl}}.{{cite book|author1=Wiberg, E.|author2=Holleman, A. F.|year = 2001|title = Inorganic Chemistry|publisher = Elsevier|isbn = 0-12-352651-5}}{{cln|What is S4N3Cl?|date=October 2022}}

{{chem2|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 {{chem2|S4N4}}. In the solid state it spontaneously polymerizes forming polythiazyl. It forms adducts with Lewis acids via a nitrogen atom, e.g. {{chem2|S2N2*BCl3}}, {{chem2|S2N2*2AlCl3}}, {{chem2|S2N2*SbCl5}}, {{chem2|S2N2*2SbCl5}}.{{cite journal|author1=Patton R. L.|author2=Raymond, K. N.|title = The Crystal and Molecular Structure of S₂N₂(SbCl₅)₂|journal = Inorganic Chemistry|year = 1969|volume = 8|issue = 11|pages = 2426–2431|doi = 10.1021/ic50081a035}}

The {{chem2|S2N2}} molecule is a four-membered ring, with alternating S and N atoms. The {{chem2|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 {{chem2|S2N2}} molecule is isoelectronic with the cyclic {{chem2|S4(2+)}} dication and has 6π electrons. The bonding has been investigated using a spin-coupled valence bond method {{cite journal|author1=Gerratt, J.|author2=McNicholas, S. J.|author3=Karadakov, P. B.|author4=Sironi, M.|author5=Raimondi, M.|author6=Cooper, D. L.|title = The Extraordinary Electronic Structure of N₂S₂|journal = Journal of the American Chemical Society|year = 1996|volume = 118|issue = 27|pages = 6472–6476|doi = 10.1021/ja953994f}} 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.

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

{{reflist}}

{{Sulfur compounds}}

{{Nitrides}}

Category:Nitrides

Category:Four-membered rings

Category:Sulfur–nitrogen compounds

Category:Explosive chemicals