Boron sulfide

Boron sulfide

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Names
IUPAC name Boron sulfide
Other names Boron trisulfide
Identifiers
CAS Number	12007-33-9 Y
Properties
Chemical formula	B2S3
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 in water	decomposes
Solubility	soluble in ammonia
Structure
Crystal structure	monoclinic, mP40, SpaceGroup = P21/c, No. 14
Coordination geometry	B: planar, sp2
Thermochemistry
Specific heat capacity (C)	111.7 J/mol K
Std molar entropy (So298)	327 J/mol K
Std enthalpy of formation (ΔfHo298)	-240.6 kJ/mol
Vapor pressure	{{{value}}}
Related compounds
Related compounds	BCl3 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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Infobox references

Boron sulfide is the chemical compound with the formula B₂S₃. This polymeric material that 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 water, including atmospheric moisture to release H₂S. Thus, samples must be handled under anhydrous conditions.

Like the boron oxides, B₂S₃ readily forms glasses when blended with other sulfides such as P₄S₁₀. Such glasses absorb lower frequencies of Infra-red energy relative to conventional borosilicate glasses.

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

B
₂S
₃ + 3 (C
₆H
₅)
₂C=O → B
₂O
₃ + 3 (C
₆H
₅)
₂C=S

In practice, B₂S₃ would be used in excess.

Synthesis

Besides other methods the Diboron Trisulfide can be obtained by the reaction of iron or manganese boride with hydrogen sulfide at temperatures of 300°C.

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°.