Bismuth compounds


forms mainly trivalent and a few pentavalent compounds. Many of its chemical properties are similar to those of arsenic and antimony, although much less toxic.

Oxides and sulfides

At elevated temperatures, vaporized bismuth metal and oxygen combine into the yellow trioxide, Bismuth oxide|. At temperatures above 710 °C, this oxide corrodes all known oxides and even platinum. It forms two series of oxyanions in basic conditions: linear, chain-polymeric ; and cubic. In, the anion forms the octamer ; in, the tetramer.
The dark red bismuth oxide,, is unstable, liberating oxygen| gas upon heating. The compound NaBiO3 is a strong oxidant.
Bismuth sulfide, Bismuth sulfide|, occurs naturally in bismuth ores, but can be synthesized from molten bismuth and sulfur.

Halides

In oxidation state +3, bismuth forms salts with all the halogens: bismuth trifluoride|, bismuth chloride|, bismuth tribromide|, and bismuth iodide|. All hydrolyze in water except. Bismuth chloride reacts with hydrogen chloride in ether solution to produce the acid.
The oxidation state +5 is less frequently encountered. One such compound is the powerful oxidant and fluorinator, bismuth pentafluoride|. It is also a strong fluoride acceptor, forming the cation from xenon tetrafluoride:
The low-oxidation-state bismuth halides adopt unusual cluster structures. What was originally thought bismuth chloride, BiCl, is in fact a lattice of Bi cations and BiCl and BiCl anions. The Bi cation has a distorted tricapped trigonal prismatic molecular geometry and is also found in, which is prepared by reducing a mixture of hafnium chloride and bismuth chloride with elemental bismuth, having the structure. Other polyatomic bismuth cations are also known, such as Bi, found in.
There is a true monoiodide, BiI, which contains chains of units. BiI decomposes upon heating to the triiodide, Bismuth iodide|, and elemental bismuth.
Bismuth forms at least two "monobromides": one isostructural to "BiCl" and one isostructural to.

Aqueous species and the bismuthyl cation

In aqueous solution, the Bi ion is solvated to form the aqua ion in strongly acidic conditions. At pH > 0 polynuclear species exist, the most important of which is believed to be the octahedral complex .
Bismuth oxychloride and bismuth oxynitrate stoichiometrically appear simple anionic salts of the bismuthyl cation, which commonly occurs in aqueous bismuth compounds. However, in the case of BiOCl, the salt crystal forms alternating plates of Bi, O, and Cl atoms. Each oxygen coordinates with four bismuth atoms in the adjacent plane.

Bismuthine and bismuthides

Unlike the lighter pnictogens nitrogen, phosphorus, and arsenic, but similar to antimony, bismuth does not form a stable hydride. Bismuth hydride, bismuthine, is an endothermic compound that spontaneously decomposes at room temperature. It is stable only below −60 °C. Bismuthides are intermetallic compounds between bismuth and other metals.
In 2014 researchers discovered that sodium bismuthide admits bulk 3D Dirac fermions. As a topological Dirac semi-metal, it is a three-dimensional counterpart to graphene with similar electron mobility and velocity. While sodium bismuthide is too unstable to be used in devices without packaging, it may offer distinct efficiency and fabrication advantages over planar graphene in semiconductor and spintronics applications.

Applications

Coloration