Tin(II) bromide

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Tin(II) bromide
SnBr2-xtal-chain-3D-bs-17.png
part of an (SnBr2)∞ chain in the solid state [1]
Names
Other names
tin dibromide, stannous bromide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.067 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 233-087-0
PubChem CID
UNII
  • InChI=1S/2BrH.Sn/h2*1H;/q;;+2/p-2 X mark.svgN
    Key: ZSUXOVNWDZTCFN-UHFFFAOYSA-L X mark.svgN
  • InChI=1/2BrH.Sn/h2*1H;/q;;+2/p-2
    Key: ZSUXOVNWDZTCFN-NUQVWONBAM
  • Br[Sn]Br
Properties
SnBr2
Molar mass 278.518 g/mol
Appearanceyellow 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]
GHS-pictogram-acid.svg
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]

Contents

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. [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]

O-SnBr2-xtal-packing-2x2x2-3D-bs-17.png
orthorhombic polymorph [1] [7]
H-SnBr2-xtal-packing-2x2x2-3D-bs-17.png
hexagonal polymorph [1] [8]

Preparation

Tin(II) bromide can be prepared by the reaction of metallic tin and HBr distilling off the H2O/HBr and cooling: [9]

Sn + 2 HBr → SnBr2 + H2

However, the reaction will produce tin (IV) bromide in the presence of oxygen.

Reactions

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 and 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.

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 [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]

References

  1. 1 2 3 4 Eckold, Pierre; Hügel, Werner; Dinnebier, Robert E.; Niewa, Rainer (2005). "Two Modifications of Tin(II) Bromide". Z. Anorg. Allg. Chem. 641 (8–9): 1467–1472. doi:10.1002/zaac.201500108.
  2. ↑ "Tin(II) bromide". pubchem.ncbi.nlm.nih.gov. Retrieved 12 December 2021.
  3. 1 2 3 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. doi:10.1016/C2009-0-30414-6. ISBN   978-0-08-037941-8.
  4. ↑ J.L Wardell "Tin:Inorganic Chemistry" Encyclopedia of Inorganic Chemistry Ed: R Bruce King John Wiley & Sons (1994) ISBN   0-471-93620-0
  5. ↑ K. Hilpert; M. Miller; F. Ramondo (1991). "Thermochemistry of tetrabromoditin and bromoiodotin gaseous". J. Phys. Chem. 95 (19): 7261–7266. doi:10.1021/j100172a031.
  6. ↑ 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. Bibcode:2000JSSCh.149...28A. doi:10.1006/jssc.1999.8489.
  7. ↑ "ICSD Entry: 429132". Cambridge Structural Database: Access Structures. Cambridge Crystallographic Data Centre . Retrieved 2022-02-09.
  8. ↑ "ICSD Entry: 429133". Cambridge Structural Database: Access Structures. Cambridge Crystallographic Data Centre. Retrieved 2022-02-09.
  9. 1 2 Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN   0-471-19957-5
  10. ↑ Bulten E.J. (1975). "A convenient synthesis of (C1-C18) alkyltin tribromides". Journal of Organometallic Chemistry. 97 (1): 167–172. doi:10.1016/S0022-328X(00)89463-2. hdl: 1874/15985 .
  11. ↑ Chung Chun Hsu & R. A. Geanangel (1977). "Synthesis and studies of trimethylamine adducts with tin(II) halides". Inorg. Chem. 16 (1): 2529–2534. doi:10.1021/ic50176a022.
  12. ↑ Chung Chun Hsu & 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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