Tin(II) bromide
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2008-05-29T14:29:39Z
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{{Chembox new
| Name = Tin(II) bromide
| ImageFile = Tin(II)_bromide.jpg
<!-- | ImageSize = 200px -->
| ImageName = Tin(II) bromide
| OtherNames = tin dibromide, stannous bromide
| Section1 = {{Chembox Identifiers
| CASNo = 10031-24-0
}}
| Section2 = {{Chembox Properties
| Formula = SnBr<sub>2</sub>
| MolarMass = 278.518 g/mol
| Appearance = yellow powder
| Density = 5.12 g/cm³, solid
| Solubility = ?
| MeltingPt = 215°C
| BoilingPt = 639°C
}}
| Section3 = {{Chembox Structure
| CrystalStruct = related to PbCl<sub>2</sub>
}}
| Section7 = {{Chembox Hazards
| EUClass = not listed
}}
}}
'''Tin(II) bromide''' is a chemical compound of [[tin]] and [[bromine]] with a chemical formula of SnBr<sub>2</sub>. Tin is in the +2 oxidation state. The stability of tin compounds in this oxidation state is attributed to the [[inert pair effect]].<ref name = "Greenwood"> {{Greenwood&Earnshaw}}</ref>
<br />
==Structure and bonding==
In the gas phase SnBr<sub>2</sub> is non-linear with a bent configuration similar to SnCl<sub>2</sub> in the gas phase. The Br-Sn-Br angle is 95° and the Sn-Br bond length is 255pm.<ref> J.L Wardell "Tin:Inorganic Chemistry" ''Encyclopedia of Inorganic Chemistry'' Ed: R Bruce King John Wiley & Sons (1994) ISBN 0-4719-3620-0</ref>There is evidence of dimerisation in the gaseous phase.<ref>{{cite journal
| title = Thermochemistry of tetrabromoditin and bromoiodotin gaseous
| author = K. Hilpert, M. Miller, F. Ramondo
| journal =J. Phys. Chem.
| year = 1991
| volume = 95
| issue = 19
| pages = 7261–7266
| doi = 10.1021/j100172a031
}}</ref> The solid state structure is related to that of [[tin(II) chloride|SnCl<sub>2</sub>]] and [[lead(II) chloride|PbCl<sub>2</sub>]] and the tin atoms have five near bromine atom neighbours in an approximately trigonal bipyramidal configuration.<ref>{{cite journal
| title = Inert Pair Effects in Tin and Lead Dihalides: Crystal Structure of Tin(II) Bromide
| author = Abrahams I.; Demetriou D.Z.
| journal =Journal of Solid State Chemistry
| year = 2000
| volume = 149
| issue = 1
| pages = 28–32
| doi = 10.1006/jssc.1999.8489
}}</ref>
==Preparation==
Tin(II) bromide can be prepared by the reaction of metallic tin and [[hydrobromic acid|HBr]] distilling off the H<sub>2</sub>O/HBr and cooling<ref name= "Cotton">{{Cotton&Wilkinson6th}}</ref>:
:Sn + 2HBr<nowiki>→</nowiki> SnBr<sub>2</sub> + H<sub>2</sub>
==Reactions==
SnBr<sub>2</sub> is soluble in donor solvents such as [[acetone]], [[pyridine]] and [[dimethylsulfoxide]] to give pyramidal adducts<ref name = "Cotton"/><br />
A number of hydrates are known,2SnBr<sub>2</sub>.H<sub>2</sub>O, 3SnBr<sub>2</sub>.H<sub>2</sub>O & 6SnBr<sub>2</sub>.5H<sub>2</sub>O which in the solid phase have tin coordinated by a distorted trigonal prism of 6 bromine atoms with Br or H<sub>2</sub>O capping 1 or 2 faces.<ref name = "Greenwood"> {{Greenwood&Earnshaw}}</ref>
When dissolved in [[hydrobromic acid|HBr]] the pyramidal SnBr<sub>3</sub><sup>−</sup> ion is formed.<ref name = "Greenwood" />
Like SnCl<sub>2</sub> it is a reducing agent. With a variety of alkyl bromides oxidative addition can occur to yield the alkyltin tribromide<ref>{{cite journal
| title = A convenient synthesis of (C<sub>1</sub>-C<sub>18</sub>) alkyltin tribromides
| author = Bulten E.J.
| journal = Journal of Oganometallic Chemistv
| year = 1975
| volume = 97
| issue = 1
| pages = 167–172
}}</ref> e.g.
:SnBr<sub>2</sub> + RBr<nowiki>→</nowiki> RSnBr<sub>3</sub>
Tin(II) bromide can act as a [[Lewis acid]] forming adducts with donor molecules e.g. [[trimethylamine]] where it forms NMe<sub>3</sub>.SnBr<sub>2</sub> and 2NMe<sub>3</sub>.SnBr<sub>2</sub>
<ref>{{cite journal
| title = Synthesis and studies of trimethylamine adducts with tin(II) halides
| author = Chung Chun Hsu and R. A. Geanangel
| journal = Inorg. Chem.
| year = 1977
| volume = 16
| issue = 1
| pages = 2529–2534
| doi = 10.1021/ic50176a022
}}</ref>
It can also act as both donor and acceptor in, for example, the complex F<sub>3</sub>B.SnBr<sub>2</sub>.NMe<sub>3</sub> where it is a donor to [[boron trifluoride]] and an acceptor to [[trimethylamine]].
<ref>{{cite journal
| title = Donor and acceptor behavior of divalent tin compounds
| author = Chung Chun Hsu and R. A. Geanangel
| journal = Inorg. Chem.
| year = 1980
| volume = 19
| issue = 1
| pages = 110–119
| doi = 10.1021/ic50203a024
}}</ref>
==References==
{{reflist}}
[[Category:Bromides]]
[[Category:Tin compounds]]
[[ar:بروميد قصدير ثنائي]]