Nickel(II) bromide is the name for the
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 ...
s with the chemical formula NiBr
2(H
2O)
''x''. The value of ''x'' can be 0 for the anhydrous material, as well as 2, 3, or 6 for the three known
hydrate
In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...
forms. The anhydrous material is a yellow-brown solid which dissolves in
water to give blue-green hexahydrate (see picture).
Structure
The structure of the nickel bromides varies with the degree of hydration. In all of these cases, the nickel(II) ion adopts an
octahedral molecular geometry
In chemistry, octahedral molecular geometry, also called square bipyramidal, describes the shape of compounds with six atoms or groups of atoms or ligands symmetrically arranged around a central atom, defining the vertices of an octahedron. The oc ...
. Similar structures are observed in aqueous solutions of nickel bromide.
*Anhydrous NiBr
2 adopts the hexagonal
cadmium chloride
Cadmium chloride is a white crystalline compound of cadmium and chloride, with the formula CdCl2. This salt is a hygroscopic solid that is highly soluble in water and slightly soluble in alcohol. The crystal structure of cadmium chloride (describe ...
structure.
The interatomic distance for Ni-Br is 2.52—2.58 Å.
Anhydrous NiBr
2 is a
paramagnet at room temperature. Upon cooling, it turns into an
antiferromagnet at 52 K, and then into a helimagnet at 22.8 K.
[
*The structure of the trihydrate has not been confirmed by X-ray crystallography. It is assumed to adopt a chain structure.
*The di- and hexahydrates adopt structures akin to those for the corresponding chlorides. The dihydrate consists of a linear chain, whereas the hexahydrate features isolated ''trans''- iBr2(H2O)4molecules together with two water molecules of crystallization.
]
Reactions and uses
NiBr2 has 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 ...
character, as indicated by its tendency to hydrate and form adducts with a variety of other Lewis bases.
NiBr2 is also used to prepare catalysts for cross-coupling reactions and various carbonylations.[ NiBr2-glyme shows increased activity compared to NiCl2-glyme for some transformations.
]
Safety
This compound is a suspected carcinogen.
References
Cited sources
*
{{bromine compounds
Nickel compounds
Bromides
Metal halides