Tin(II) bromide

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]

Tin(II) bromide

part of an (SnBr2)∞ chain in the solid state[1]
Names
Other names tin dibromide, stannous bromide
Identifiers
CAS Number	10031-24-0 Y
3D model (JSmol)	Interactive image
ChemSpider	59609 Y
ECHA InfoCard	100.030.067
EC Number	233-087-0
PubChem CID	66224
UNII	55F23H2K96 Y
CompTox Dashboard (EPA)	DTXSID501015689 DTXSID70830932, DTXSID501015689
InChI InChI=1S/2BrH.Sn/h2*1H;/q;;+2/p-2 N Key: ZSUXOVNWDZTCFN-UHFFFAOYSA-L N InChI=1/2BrH.Sn/h2*1H;/q;;+2/p-2 Key: ZSUXOVNWDZTCFN-NUQVWONBAM
SMILES Br[Sn]Br
Properties
Chemical formula	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
Crystal structure	related to PbCl2
Hazards
GHS labelling:[2]
Pictograms
Signal word	Danger
Hazard statements	H314
Precautionary statements	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). N verify (what is YN ?) Infobox references

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]

orthorhombic polymorph^[1][7]

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 & 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]