Disulfur dinitride is the chemical compound with the formula .

Preparation and reactions

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

An alternative uses the less explosive .

decomposes explosively above 30°C, and is shock sensitive. It readily sublimes, and is soluble in diethyl ether. Traces of water or other nucleophiles cause it to polymerize into . In the solid state it spontaneously polymerizes forming (SN)_{n}, catalyzed by radical impurities. It forms adducts with Lewis acids via a nitrogen atom, e.g. , , , .

Structure and bonding

The 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°.

The molecule is isoelectronic with the cyclic dication, but the oft-quoted description of 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 are each nonbonding orbitals corresponding to these two electrons.

See also

• Sulfur nitride

• Tetrasulfur tetranitride

• Polythiazyl

• Square planar molecular geometry

References