Hydrogen selenide
General
Systematic name	Hydrogen selenide
Other names	Hydroselenic acid selane selenium hydride
Molecular formula	H2Se
Molar mass	80.9758 g/mol
Appearance	Colorless gas.
CAS number
Properties
Density and phase	3.310 g/l, gas.
Solubility in water	0.70 g/100 mL
Melting point	-65.73°C (207.42 K)
Boiling point	-41.25°C (231.9 K)
Acidity (pKa)	See Text
Structure
Molecular shape	Planar.
Dipole moment	? D
Hazards
MSDS	External MSDS
Main hazards	Highly toxic, highly flammable, corrosive
NFPA 704
Flash point	?°C
R/S statement	R: , , S: ?
RTECS number	X1050000
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other anions	Hydrogen fluoride hydrogen chloride hydrogen bromide hydrogen iodide
Other cations	?
Related compounds	?
Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Chemical infobox

Hydrogen selenide is H₂Se, the simplest hydride of selenium. H₂Se is a colorless, flammable gas under standard conditions. It is the most toxic selenium compound with an exposure limit: 0.3 ppm over an 8 hour period.

Structure

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H₂Se adopts a "bent" structure with a H-Se-H bond angle of 91°. Consistent with this structure, three IR-active vibrational bands are observed: 2358, 2345, and 1034 cm^-1.

Properties

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The properties of H₂S and H₂Se are somewhat similar, although the selenide is more acidic with pK_a = 3.89, and the second pK_a = 11.0 at 25°C. Reflecting its acidity, H₂Se is soluble in water.

Preparation

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H₂Se can be purchased in cylinders. A number of routes to H₂Se have been reported, which are suitable for both large and small scale preparations.

• H₂Se is usually prepared by the action of water on Al₂Se₃, concomitant with formation of hydrated alumina. A related reaction involves the acid hydrolysis of FeSe.

Al₂Se₃ + 6 H₂O 2 Al(OH)₃ + 3 H₂Se

• According to the Sonoda method, H₂Se is generated from the reactionof H₂O and CO on Se in the presence of Et₃N.
• H₂Se can by synthesized by the direct reaction of H₂ with elemental selenium at >350°C.

Selenium metal can be recovered from H₂Se through a reaction with aqueous sulfur dioxide (SO₂).

2 H₂Se + SO₂ 2 H₂O + Se + S

Applications

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• H₂Se is commonly used in the synthesis of Se-containing compounds; it adds across alkenes. Illustrative is the synthesis of selenoureas from nitriles.
  • H₂Se gas is used to dope semiconductors with selenium.

  References

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  1. Patnaik, Pradyot Handbook of Inorganic Chemicals. McGraw-Hill Handbooks New York (2003).
  2. V.I. Cohen, Synthesis 1:60-3 (1980).
  3. Greenwood, N. N., Earnshaw, A. Chemistry of the Elements Second Ed. Butterworth-Heinemann, Boston (1997).
  4. CRC Handbook of Chemistry and Physics Ed. 82. Chapman and Hall (2001-2002).
  • Feher, F. In "Handbook of Preparative Inorganic Chemistry"; Brauer, E., Ed.; Academic: New York, 1963; 1, p 418.
  • Sonoda, N.; Kondo K.; Nagano, K.; Kambe, N.; Morimoto, F. Angewandte Chemie, International Edition English 1980, vol. 19, page 308

  External links

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  • WebElements page on compound's properties

  Hydrogen compounds | Selenides

  セレン化水素