Tin(II) bromide

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Tin(II) bromide
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 disclaimer and references

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]

Contents

[edit] 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]

[edit] 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

[edit] 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]

[edit] References

  1. ^ a b c Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4. 
  2. ^ J.L Wardell "Tin:Inorganic Chemistry" Encyclopedia of Inorganic Chemistry Ed: R Bruce King John Wiley & Sons (1994) ISBN 0-4719-3620-0
  3. ^ K. Hilpert, M. Miller, F. Ramondo (1991). "Thermochemistry of tetrabromoditin and bromoiodotin gaseous". J. Phys. Chem. 95 (19): 7261–7266. doi:10.1021/j100172a031. 
  4. ^ 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:10.1006/jssc.1999.8489. 
  5. ^ 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.
  6. ^ Bulten E.J. (1975). "A convenient synthesis of (C1-C18) alkyltin tribromides". Journal of Oganometallic Chemistv 97 (1): 167–172. 
  7. ^ 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:10.1021/ic50176a022. 
  8. ^ Chung Chun Hsu and R. A. Geanangel (1980). "Donor and acceptor behavior of divalent tin compounds". Inorg. Chem. 19 (1): 110–119. doi:10.1021/ic50203a024. 
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