part of an (SnBr2)∞ chain in the solid state
[1]
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Names | |
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Other names
tin dibromide, stannous bromide
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Identifiers | |
3D model (
JSmol)
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ChemSpider | |
ECHA InfoCard | 100.030.067 |
EC Number |
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PubChem
CID
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UNII | |
CompTox Dashboard (
EPA)
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Properties | |
SnBr2 | |
Molar mass | 278.518 g/mol |
Appearance | yellow powder |
Density | 5.12 g/cm3, solid |
Melting point | 215 °C (419 °F; 488 K) |
Boiling point | 639 °C (1,182 °F; 912 K) |
Structure | |
related to PbCl2 | |
Hazards | |
GHS labelling: [2] | |
Danger | |
H314 | |
P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501 | |
Except where otherwise noted, data are given for materials in their
standard state (at 25 °C [77 °F], 100 kPa).
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Tin(II) bromide is a chemical compound of tin and bromine with a chemical formula of SnBr2. Tin is in the +2 oxidation state. The stability of tin compounds in this oxidation state is attributed to the inert pair effect. [3]
In the gas phase SnBr2 is non-linear with a bent configuration similar to SnCl2 in the gas phase. The Br-Sn-Br angle is 95° and the Sn-Br bond length is 255pm. [4] There is evidence of dimerisation in the gaseous phase. [5] 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. [6] Two polymorphs exist: a room-temperature orthorhombic polymorph, and a high-temperature hexagonal polymorph. Both contain (SnBr2)∞ chains but the packing arrangement differs. [1]
Tin(II) bromide can be prepared by the reaction of metallic tin and HBr distilling off the H2O/HBr and cooling: [9]
However, the reaction will produce tin (IV) bromide in the presence of oxygen.
SnBr2 is soluble in donor solvents such as
acetone,
pyridine and
dimethylsulfoxide to give pyramidal adducts.
[9]
A number of hydrates are known, 2SnBr2·H2O, 3SnBr2·H2O & 6SnBr2·5H2O which in the solid phase have tin coordinated by a distorted trigonal prism of 6 bromine atoms with Br or H2O capping 1 or 2 faces.
[3]
When dissolved in
HBr the pyramidal SnBr3− ion is formed.
[3]
Like SnCl2 it is a reducing agent. With a variety of alkyl bromides oxidative addition can occur to yield the alkyltin tribromide
[10] e.g.
Tin(II) bromide can act as a Lewis acid forming adducts with donor molecules e.g. trimethylamine where it forms NMe3·SnBr2 and 2NMe3·SnBr2 [11] It can also act as both donor and acceptor in, for example, the complex F3B·SnBr2·NMe3 where it is a donor to boron trifluoride and an acceptor to trimethylamine. [12]