[biz-muh-theen, -thin]
Bismuthine is the chemical compound with the formula BiH3. As the heaviest analogue of ammonia, BiH3 is unstable, decomposing to bismuth metal well below 0 °C. In fact, the compound has only been characterized (by infra-red spectroscopy and microwave spectroscopy) as a component of a mixture. This compound is also predicted to have a pyramidal structure with H-Bi-H angles of 90°. Bismuthines also describes a family of organobismuth(III) species; for example Bi(CH3)3 is trimethylbismuthine.

Preparation and properties

BiH3 is prepared by the redistribution of methylbismuthine BiH2Me:
3 BiH2Me → 2 BiH3 + BiMe3
The required BiH2Me, which is also thermally unstable, is generated by reduction of methylbismuth dichloride, BiCl2Me with LiAlH4.

As suggested by the behavior of SbH3, BiH3 is unstable with respect to its elements. The gas decomposes according to the following equation:

2 BiH3 → 3 H2 + 2 Bi
ΔHf'ogas = −278 kJ/mol

The methodology used for detection of arsenic ("Marsh Test") can also be used to detect BiH3. This test relies on the thermal decomposition of these trihydrides to the metallic mirrors of metallic As, Sb, and Bi. These deposits can be further distinguished by their distinctive solubility characteristics: As dissolves in NaOCl, Sb dissolves in ammonium polysulfide, and Bi resists both reagents.

Uses and safety considerations

The low stability of BiH3 preclude significant hazards and technical applications.


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