Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references
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.
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
The properties of H2S and H2Se are similar, although the selenide is more acidic with pKa = 3.89, and the second pKa = 11.0 at 25°C. Reflecting its acidity, H2Se is soluble in water.
Preparation
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 reaction of 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
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
The references in this article would be clearer with a different or consistent style of citation, footnoting, or external linking.
Patnaik, Pradyot Handbook of Inorganic Chemicals. McGraw-Hill Handbooks New York (2003).
V.I. Cohen, Synthesis 1:60-3 (1980).
Greenwood, N. N., Earnshaw, A. Chemistry of the Elements Second Ed. Butterworth-Heinemann, Boston (1997).
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
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