Boron sulfide is the chemical compound with the formula B<sub>2</sub>S<sub>3</sub>. It is a white, moisture-sensitive solid. It has a polymeric structure. The material has been of interest as a component of "high-tech" glasses and as a reagent for preparing organosulfur compounds. It is the parent member of the thioborates.
Like the sulfides of silicon and phosphorus, B<sub>2</sub>S<sub>3</sub> reacts with traces of water, including atmospheric moisture to release H<sub>2</sub>S. This hydrolysis is described by the following idealized equation:
B<sub>2</sub>S<sub>3</sub> readily forms glasses when blended with other sulfides such as P<sub>4</sub>S<sub>10</sub>. Such glasses do not absorb mid-frequencies of Infra-red energy relative to conventional borosilicate glasses. Some of these ternary phases that are fast ion conductors.
B<sub>2</sub>S<sub>3</sub> converts ketones into the corresponding thiones. For example, the conversion of benzophenone to its thione proceeds as follows:
In practice, B<sub>2</sub>S<sub>3</sub> would be used in excess.
An early synthesis involved the reaction of iron and manganese borides with hydrogen sulfide at temperatures of 300 ðC. The conversion is shown for the monoborides in the following idealized equation:
The first synthesis was done by Jöns Jakob Berzelius in 1824 by direct reaction of amorphous boron with sulfur vapor.
Another synthesis was favoured by Friedrich Wöhler and Henri Etienne Sainte-Claire Deville first published in 1858, starting from boron and hydrogen sulfide.
The boron atoms in B<sub>2</sub>S<sub>3</sub> are trigonal planar, and are arranged in B<sub>3</sub>S<sub>3</sub> and B<sub>2</sub>S<sub>2</sub> rings with bridging S atoms forming a layer structure with an interlayer distance of 355 pm. This is different from boron trioxide which has a three dimensional structure. The molecular, monomeric, form of B<sub>2</sub>S<sub>3</sub> has a planar V shape with the central B-S-B angle of approximately 120ð.