Stibine (IUPAC name: stibane) is a chemical compound with the formula AntimonyHydrogen3. A pnictogen hydride, this colourless, highly toxic gas is the principal covalent hydride of antimony, and a heavy analogue of ammonia. The molecule is pyramidal with H–Sb–H angles of 91.7° and Sb–H distances of 170.7 picometre (1.707 Å). The smell of this compound from usual sources (like from reduction of antimony compounds) is reminiscent of arsine, i.e. garlic-like.
Preparation
SbH
3 is generally prepared by the reaction of Sb
3+ sources with H− equivalents:
- 2 Sb2O3 + 3 LiAlH4 → 4 SbH3 + 1.5 Li2O + 1.5 Al2O3
- 4 SbCl3 + 3 NaBH4 → 4 SbH3 + 3 NaCl + 3 BCl3
Alternatively, sources of Sb3− react with protonic reagents (even water) to also produce this unstable gas:
- Na3Sb + 3 H2O → SbH3 + 3 NaOH
Properties
The chemical properties of SbH
3 resemble those for
arsine.
Typical for a heavy hydride (e.g. AsH
3, H
2Te, SnH
4), SbH
3 is unstable with respect to its elements. The gas decomposes slowly at room temperature but rapidly at 200 °C:
- :2 SbH3 → 3 H2 + 2 Sb
The decomposition is
autocatalytic and can be explosive.
SbH3 is readily oxidation by O2 or even air:
- :2 SbH3 + 3 O2 → Sb2O3 + 3 H2O
SbH3 exhibits no basicity, but it can be deprotonated:
- :SbH3 + sodium amide → NaSbH2 + NH3
The salt is called sodium stibinide, and contains the stibinide anion .
Uses
Stibine is used in the
semiconductor industry to dope silicon with small quantities of
antimony via the process of chemical vapour deposition (CVD). It has also been used as a silicon dopant in epitaxial layers. Reports claim the use of SbH
3 as a
fumigation but its instability and awkward preparation contrast with the more conventional fumigant
phosphine.
History
As stibine (SbH
3) is similar to
arsine (AsH
3); it is also detected by the
Marsh test. This sensitive test detects arsine generated in the presence of
arsenic.
This procedure, developed circa 1836 by James Marsh, treats a sample with arsenic-free
zinc and dilute
sulfuric acid: if the sample contains arsenic, gaseous arsine will form. The gas is swept into a glass tube and decomposed by means of heating around 250 – 300 °C. The presence of arsenic is indicated by formation of a deposit in the heated part of the equipment. The formation of a black mirror deposit in the cool part of the equipment indicates the presence of
antimony.
In 1837 Lewis Thomson and Pfaff independently discovered stibine. It took some time before the properties of the toxic gas could be determined, partly because a suitable synthesis was not available. In 1876 Francis Jones tested several synthesis methods,
Safety
SbH
3 is an unstable flammable gas. It is highly toxic, with an LC50 of 100 ppm in mice.
Toxicology
The toxicity of stibine is distinct from that of other
antimony compounds, but similar to that of
arsine.
Stibine binds to the
haemoglobin of red blood cells, causing them to be destroyed by the body. Most cases of stibine poisoning have been accompanied by arsine poisoning, although animal studies indicate that their toxicities are equivalent. The first signs of exposure, which can take several hours to become apparent, are
, vertigo, and
nausea, followed by the symptoms of
hemolytic anemia (high levels of unconjugated
bilirubin),
hemoglobinuria, and
nephropathy.
See also
-
Antimony (Sb)
-
Arsine (AsH3)
-
Devarda's alloy, also used to produce arsine and stibine in the lab
-
List of highly toxic gases
-
Marsh test, first used to analyse AsH3 and SbH3
-
James Marsh, invented the Marsh test in 1836
-
Nascent hydrogen
External links
