Boron sulfide

Boron sulfide is the chemical compound with the formula B2S3. 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.

Reactions
Like the sulfides of silicon and phosphorus, B2S3 reacts with traces of water, including atmospheric moisture to release H2S. This hydrolysis is described by the following idealized equation:
 * B2S3 + 3 H2O  ->  B2O3  +  3 H2S

B2S3 readily forms glasses when blended with other sulfides such as P4S10. 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.

B2S3 converts ketones into the corresponding thiones. For example, the conversion of benzophenone to its thione proceeds as follows:
 * B2S3 + 3 (C6H5)2C\dO -> B2O3 + 3 (C6H5)2C\dS

In practice, B2S3 would be used in excess.

Synthesis
An early synthesis involved the reaction of iron and manganese borides with hydrogen sulfide at temperatures of 300 °C. The conversion is shown for the monoborides in the following idealized equation:
 * 2 FeB + 4 H2S  →  B2S3 +  FeS + 4 H2

The first synthesis was done by Jöns Jakob Berzelius in 1824 by direct reaction of amorphous boron with sulfur vapor.
 * 2 B +  3 S  →  B2S3

Another synthesis was favoured by Friedrich Wöhler and Henri Etienne Sainte-Claire Deville first published in 1858, starting from boron and hydrogen sulfide.


 * 2 B +  3 H2S  →  B2S3  +  3 H2

Structure
The boron atoms in B2S3 are trigonal planar, and are arranged in B3S3 and B2S2 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 B2S3 has a planar V shape with the central B-S-B angle of approximately 120°.