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| Tin(II) bromide | |
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| Image:Tin(II) bromide.jpg | |
| Other names | tin dibromide, stannous bromide |
| Identifiers | |
| CAS number | [10031-24-0] |
| Properties | |
| Molecular formula | SnBr2 |
| Molar mass | 278.518 g/mol |
| Appearance | yellow powder |
| Density | 5.12 g/cm³, solid |
| Melting point |
215°C |
| Boiling point |
639°C |
| Solubility in water | ? |
| Structure | |
| Crystal structure | related to PbCl2 |
| Hazards | |
| EU classification | not listed |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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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.[1]
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Structure and bonding
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.[2]There is evidence of dimerisation in the gaseous phase.[3] 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.[4]
Preparation
Tin(II) bromide can be prepared by the reaction of metallic tin and HBr distilling off the H2O/HBr and cooling[5]:
- Sn + 2HBr→ SnBr2 + H2
Reactions
SnBr2 is soluble in donor solvents such as acetone, pyridine and dimethylsulfoxide to give pyramidal adducts[5]
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.[1] When dissolved in HBr the pyramidal SnBr3− ion is formed.[1] Like SnCl2 it is a reducing agent. With a variety of alkyl bromides oxidative addition can occur to yield the alkyltin tribromide[6] e.g.
- SnBr2 + RBr→ RSnBr3
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 [7] 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. [8]
References
- ^ a b c Greenwood, Norman N.; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford: Butterworth-Heinemann. ISBN 0-7506-3365-4.
- ^ J.L Wardell "Tin:Inorganic Chemistry" Encyclopedia of Inorganic Chemistry Ed: R Bruce King John Wiley & Sons (1994) ISBN 0-4719-3620-0
- ^ K. Hilpert, M. Miller, F. Ramondo (1991). "Thermochemistry of tetrabromoditin and bromoiodotin gaseous". J. Phys. Chem. 95 (19): 7261–7266. doi:.
- ^ Abrahams I.; Demetriou D.Z. (2000). "Inert Pair Effects in Tin and Lead Dihalides: Crystal Structure of Tin(II) Bromide". Journal of Solid State Chemistry 149 (1): 28–32. doi:.
- ^ a b Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999). Advanced Inorganic Chemistry (6th Edn.) New York:Wiley-Interscience. ISBN 0-471-19957-5.
- ^ Bulten E.J. (1975). "A convenient synthesis of (C1-C18) alkyltin tribromides". Journal of Oganometallic Chemistv 97 (1): 167–172.
- ^ Chung Chun Hsu and R. A. Geanangel (1977). "Synthesis and studies of trimethylamine adducts with tin(II) halides". Inorg. Chem. 16 (1): 2529–2534. doi:.
- ^ Chung Chun Hsu and R. A. Geanangel (1980). "Donor and acceptor behavior of divalent tin compounds". Inorg. Chem. 19 (1): 110–119. doi:.
