Boron sulfide
IUPAC name
Boron sulfide
Other names
Boron sesquisulfide, Diboron trisulfide
3D model (JSmol)
ECHA InfoCard 100.031.355 Edit this at Wikidata
EC Number
  • 234-504-9
  • InChI=1S/B2S3/c3-1-5-2-4
  • S=BSB=S
Molar mass 117.80 g/mol
Appearance colorless crystals
Density 1.55 g/cm3, solid
Melting point 563 °C (1,045 °F; 836 K)
Boiling point decomposes at high T
Solubility soluble in ammonia
monoclinic, mP40, SpaceGroup = P21/c, No. 14
B: planar, sp2
111.7 J/mol K
327 J/mol K
-240.6 kJ/mol
Occupational safety and health (OHS/OSH):
Main hazards
source of H2S
GHS labelling:
GHS02: FlammableGHS06: ToxicGHS07: Exclamation mark
H225, H260, H301, H311, H315, H318, H335
P210, P223, P231+P232, P280, P302+P352, P303+P361+P353, P305+P351+P338, P312, P402+P404, P405
NFPA 704 (fire diamond)
Flash point 18°C (64.4°F)
Safety data sheet (SDS)
Related compounds
Related compounds
Lawesson's reagent
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.


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.[2]

B2S3 converts ketones into the corresponding thiones. For example, the conversion of benzophenone to its thione proceeds as follows:

B2S3 + 3 (C6H5)2C=O → B2O3 + 3 (C6H5)2C=S

In practice, B2S3 would be used in excess.[3]


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:[4]

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.[5]

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.[6][7]

2 B + 3 H2S → B2S3 + 3 H2


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.[8] The molecular, monomeric, form of B2S3 has a planar V shape with the central B-S-B angle of approximately 120°.[8]


  1. ^ Material Safety Data Sheet, VWR, 2010, retrieved November 11, 2023
  2. ^ Kincs, Joseph; Martin, Steve W. (1996). "Non-Arrhenius Conductivity in Glass: Mobility and Conductivity Saturation Effects". Physical Review Letters. 76 (1): 70–73. Bibcode:1996PhRvL..76...70K. doi:10.1103/physrevlett.76.70. PMID 10060436.
  3. ^ Sato, R. (2004). "Boron Trisulfide". In L. Paquette (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X.rb255. ISBN 0471936235.
  4. ^ Hoffmann, J. (1908). "Synthese von Borsulfid aus Ferro- und Manganbor". Zeitschrift für anorganische Chemie. 59 (1): 127–135. doi:10.1002/zaac.19080590116.
  5. ^ Berzelius, J. (1824). "Undersökning af flusspatssyran och dess märkvärdigaste föreningar" [Investigation of hydrofluoric acid and of its most noteworthy compounds]. Kongliga Vetenskaps-Academiens Handlingar [Proceedings of the Royal Science Academy]. 12: 46–98.
    Reprinted in German as:
    Berzelius, J. J. (1824). "Untersuchungen über die Flußspathsäure und deren merkwürdigsten Verbindungen". Annalen der Physik und Chemie. 78 (10): 113–150. Bibcode:1824AnP....78..113B. doi:10.1002/andp.18240781002. see especially pages 145–147.
  6. ^ Wöhler, F.; Deville, H. E. S.-C. (1858). "Neue Beobachtungen über das Bor und einige seiner Verbindungen" [New observations concerning boron and some of its compounds]. Liebigs Annalen der Chemie und Pharmacie. 105 (1): 67–73. doi:10.1002/jlac.18581050109.
  7. ^ Wöhler, F.; Deville, H. E. S.-C. (1858). "Du Bore". Annales de Chimie et de Physique. 52: 62–93.
  8. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.