Silicon disulfide is the inorganic compound with the formula SiS<sub>2</sub>. Like silicon dioxide, this material is polymeric, but it adopts a 1-dimensional structure quite different from the usual forms of SiO<sub>2</sub>.
The material is formed by heating silicon and sulfur or by the exchange reaction between SiO<sub>2</sub> and Al<sub>2</sub>S<sub>3</sub>. The material consists of chains of edge-shared tetrahedra, -Si(ü-S)<sub>2</sub>Si(ü-S)<sub>2</sub>-.
Like other silicon sulfur-compounds (e.g., bis(trimethylsilyl)sulfide) SiS<sub>2</sub> hydrolyzes readily to release H<sub>2</sub>S. In liquid ammonia it is reported to form the imide Si(NH)<sub>2</sub> and NH<sub>4</sub>SH, but a recent report has identified crystalline (NH<sub>4</sub>)<sub>2</sub>[SiS<sub>3</sub>(NH<sub>3</sub>)]÷2NH<sub>3</sub> as a product which contains the tetrahedral thiosilicate anion, SiS<sub>3</sub>(NH<sub>3</sub>)<sup>2-</sup>.
Reaction with ethanol gives the alkoxide tetraethyl orthosilicate and H<sub>2</sub>S. With bulky tert-butanol, alcoholysis gives tris(tert-butoxy)silanethiol:
Reaction with sodium sulfide, magnesium sulfide and aluminum sulfide give thiosilicates.
SiS<sub>2</sub> is claimed to occur in certain interstellar objects.