Bismuth chloride (or butter of bismuth) is an
inorganic compound
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...
with the chemical formula BiCl
3. It is a covalent compound and is the common source of the Bi
3+ ion. In the gas phase and in the crystal, the species adopts a pyramidal structure, in accord with
VSEPR theory.
Preparation
Bismuth chloride can be synthesized directly by passing
chlorine over
bismuth.
:2 Bi + 3 Cl
2 → 2 BiCl
3
or by dissolving bismuth metal in
aqua regia, evaporating the mixture to give BiCl
3·2H
2O, which can be distilled to form the anhydrous trichloride.
Alternatively, it may be prepared by adding
hydrochloric acid to
bismuth oxide and evaporating the solution.
:Bi
2O
3 + 6 HCl → 2 BiCl
3 + 3 H
2O
Also, the compound can be prepared by dissolving bismuth in concentrated
nitric acid and then adding solid
sodium chloride
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...
into this solution.
:Bi + 6 HNO
3 → Bi(NO
3)
3 + 3 H
2O + 3 NO
2
:Bi(NO
3)
3 + 3 NaCl → BiCl
3 + 3 NaNO
3
Structure
In the gas phase BiCl
3 is pyramidal with a Cl–Bi–Cl angle of 97.5° and a bond length of 242 pm. In the solid state, each Bi atom has three near neighbors at 250 pm, two at 324 pm and three at a mean of 336 pm,
[Wells A.F. (1984) ''Structural Inorganic Chemistry'' 5th edition, pp. 879–884, Oxford Science Publications, ] the image above highlights the three closest neighbours. This structure is similar to that of
AsCl3, AsBr
3,
SbCl3 and SbBr
3.
Chemistry
Bismuth chloride is
hydrolyzed
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis ...
readily to
bismuth oxychloride, BiOCl:
:(aq) + (aq) + (l) ⇌ BiOCl (s) + 2 (aq)
This reaction can be reversed by adding an acid, such as
hydrochloric acid.
Reaction of solid BiCl
3 with water vapour below 50 °C has been shown to produce the intermediate monohydrate, BiCl
3·H
2O.
Bismuth chloride is an oxidizing agent, being readily reduced to metallic bismuth by reducing agents.
Chloro complexes
In contrast to the usual expectation by consistency with periodic trends, BiCl
3 is a
Lewis acid
A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...
, forming a variety of chloro complexes such as
iCl6sup>3− that strongly violates the
octet rule. Furthermore, the octahedral structure of this
coordination complex does not follow the predictions of VSEPR theory, since the
lone pair
In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bondIUPAC ''Gold Book'' definition''lone (electron) pair''/ref> and is sometimes called an unshared pair or non-bonding pair. Lone ...
on bismuth is unexpectedly stereochemically inactive. The dianionic complex
iCl5sup>2− does however adopt the expected square pyramidal structure.
Organic catalysis
Bismuth chloride is used as a
catalyst in
organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
. In particular, it catalyzes the
Michael reaction and the
Mukaiyama aldol reaction. The addition of other metal
iodides increases its catalytic activity.
References
{{DEFAULTSORT:Bismuth Chloride
Bismuth compounds
Chlorides
Metal halides