Bismuthine (IUPAC name: bismuthane) is the
chemical compound with the formula BiH
3. As the heaviest analogue of
ammonia (a
pnictogen hydride), BiH
3 is unstable, decomposing to
bismuth metal well below 0 °C. This compound adopts the expected pyramidal structure with H–Bi–H angles of around 90°.
The term ''bismuthine'' may also refer to a member of the family of organobismuth(III) species having the general formula , where R is an organic substituent. For example, Bi(CH
3)
3 is ''trimethylbismuthine''.
Preparation and properties
BiH
3 is prepared by the redistribution of methylbismuthine (BiH
2Me):
[Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001..]
:3 BiH
2Me → 2 BiH
3 + BiMe
3
The required BiH
2Me, which is also thermally unstable, is generated by reduction of
methylbismuth dichloride
Methylbismuth dichloride is the organobismuth compound with the formula CH3BiCl2. It is a pale yellow solid. The compound can be prepared in two steps from diphenylbismuth chloride, first by methylation with methylmagnesium chloride. Treatment o ...
, BiCl
2Me with
LiAlH4.
As suggested by the behavior of
SbH3, BiH
3 is unstable and decomposes to its constituent elements according to the following equation:
:2 BiH
3 → 3 H
2 + 2 Bi (Δ''H''(gas) = −278 kJ/mol)
The methodology used for detection of
arsenic ("
Marsh test
The Marsh test is a highly sensitive method in the detection of arsenic, especially useful in the field of forensic toxicology when arsenic was used as a poison. It was developed by the chemist James Marsh and first published in 1836. The method ...
") can also be used to detect BiH
3. This test relies on the
thermal decomposition of these trihydrides to the metallic mirrors of reduced As, Sb, and Bi. These deposits can be further distinguished by their distinctive solubility characteristics: arsenic dissolves in
NaOCl, antimony dissolves in
ammonium polysulfide
The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary amm ...
, and bismuth resists both reagents.
[
]
Uses and safety considerations
The low stability of BiH3 precludes significant health effects, it decomposes rapidly well below room temperature.
References
{{Hydrides by group
Bismuth compounds
Metal hydrides