Tin(II) bromide is a chemical compound of
tin and
bromine
Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table ( halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simi ...
with a chemical formula of SnBr
2. Tin is in the +2 oxidation state. The stability of tin compounds in this oxidation state is attributed to the
inert pair effect.
Structure and bonding
In the gas phase SnBr
2 is non-linear with a bent configuration similar to SnCl
2 in the gas phase. The Br-Sn-Br angle is 95° and the Sn-Br bond length is 255pm. There is evidence of dimerisation in the gaseous phase. The
solid state structure is related to that of
SnCl2 and
PbCl2 and the tin atoms have five near bromine atom neighbours in an approximately trigonal bipyramidal configuration. Two polymorphs exist: a room-temperature orthorhombic polymorph, and a high-temperature hexagonal polymorph. Both contain (SnBr
2)
∞ chains but the packing arrangement differs.
Preparation
Tin(II) bromide can be prepared by the reaction of metallic tin and
HBr distilling off the H
2O/HBr and cooling:
:Sn + 2 HBr → SnBr
2 + H
2
However, the reaction will produce tin (IV) bromide in the presence of oxygen.
Reactions
SnBr
2 is soluble in donor solvents such as
acetone
Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour.
Acetone is miscibl ...
,
pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid w ...
and
dimethylsulfoxide to give pyramidal adducts.
A number of hydrates are known, 2SnBr
2·H
2O, 3SnBr
2·H
2O & 6SnBr
2·5H
2O which in the solid phase have tin coordinated by a distorted trigonal prism of 6 bromine atoms with Br or H
2O capping 1 or 2 faces.
When dissolved in
HBr the pyramidal SnBr
3− ion is formed.
Like SnCl
2 it is a reducing agent. With a variety of alkyl bromides oxidative addition can occur to yield the alkyltin tribromide e.g.
:SnBr
2 + RBr → RSnBr
3
Tin(II) bromide can act as 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 adducts with donor molecules e.g.
trimethylamine
Trimethylamine (TMA) is an organic compound with the formula N(CH3)3. It is a colorless, hygroscopic, and flammable tertiary amine. It is a gas at room temperature but is usually sold as a 40% solution in water. (It is also sold in pressurized ...
where it forms NMe
3·SnBr
2 and 2NMe
3·SnBr
2
It can also act as both donor and acceptor in, for example, the complex F
3B·SnBr
2·NMe
3 where it is a donor to
boron trifluoride
Boron trifluoride is the inorganic compound with the formula BF3. This pungent, colourless, and toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds.
Structure and bond ...
and an acceptor to
trimethylamine
Trimethylamine (TMA) is an organic compound with the formula N(CH3)3. It is a colorless, hygroscopic, and flammable tertiary amine. It is a gas at room temperature but is usually sold as a 40% solution in water. (It is also sold in pressurized ...
.
References
{{bromine compounds
Bromides
Metal halides
Tin(II) compounds
Reducing agents