Tin(II) bromide
{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 428749496
| Name = Tin(II) bromide
| ImageFile = SnBr2-xtal-chain-3D-bs-17.png
| ImageName =
| ImageCaption = part of an (SnBr2)∞ chain in the solid state{{ cite journal | title = Two Modifications of Tin(II) Bromide | first1 = Pierre | last1 = Eckold | first2 = Werner | last2 = Hügel | first3 = Robert E. | last3 = Dinnebier | first4 = Rainer | last4 = Niewa | journal = Z. Anorg. Allg. Chem. | year = 2005 | volume = 641 | issue = 8–9 | pages = 1467–1472 | doi = 10.1002/zaac.201500108 }}
| OtherNames = tin dibromide, stannous bromide
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 10031-24-0
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 55F23H2K96
| PubChem = 66224
| EINECS = 233-087-0
| SMILES = Br[Sn]Br
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 59609
| InChI = 1/2BrH.Sn/h2*1H;/q;;+2/p-2
| InChIKey = ZSUXOVNWDZTCFN-NUQVWONBAM
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/2BrH.Sn/h2*1H;/q;;+2/p-2
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = ZSUXOVNWDZTCFN-UHFFFAOYSA-L
}}
|Section2={{Chembox Properties
| Formula = SnBr2
| MolarMass = 278.518 g/mol
| Appearance = yellow powder
| Density = 5.12 g/cm3, solid
| Solubility =
| MeltingPtC = 215
| BoilingPtC = 639
}}
|Section3={{Chembox Structure
| CrystalStruct = related to PbCl2
}}
|Section7={{Chembox Hazards
| GHSPictograms = {{GHS05}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|314}}
| PPhrases = {{P-phrases|260|264|280|301+330+331|303+361+353|304+340|305+351+338|310|321|363|405|501}}
}}
}}
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.{{Greenwood&Earnshaw}}
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.J.L Wardell "Tin:Inorganic Chemistry" Encyclopedia of Inorganic Chemistry Ed: R Bruce King John Wiley & Sons (1994) {{ISBN|0-471-93620-0}} There is evidence of dimerisation in the gaseous phase.{{cite journal
| title = Thermochemistry of tetrabromoditin and bromoiodotin gaseous
|author1=K. Hilpert |author2=M. Miller |author3=F. Ramondo | journal =J. Phys. Chem.
| year = 1991
| volume = 95
| issue = 19
| pages = 7261–7266
| doi = 10.1021/j100172a031
}} 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.{{cite journal
| title = Inert Pair Effects in Tin and Lead Dihalides: Crystal Structure of Tin(II) Bromide
|author1=Abrahams I. |author2=Demetriou D.Z. | journal =Journal of Solid State Chemistry
| year = 2000
| volume = 149
| issue = 1
| pages = 28–32
| doi = 10.1006/jssc.1999.8489
| bibcode = 2000JSSCh.149...28A }} Two polymorphs exist: a room-temperature orthorhombic polymorph, and a high-temperature hexagonal polymorph. Both contain (SnBr2)∞ chains but the packing arrangement differs.
{{multiple image
| align = none
| direction = horizontal
| total_width = 500
| image1 = o-SnBr2-xtal-packing-2x2x2-3D-bs-17.png
| caption1 = orthorhombic polymorph{{ Cite journal | url = https://www.ccdc.cam.ac.uk/structures/Search?Ccdcid=1737946&DatabaseToSearch=Published | title = ICSD Entry: 429132 | website = Cambridge Structural Database: Access Structures | publisher = Cambridge Crystallographic Data Centre | access-date = 2022-02-09 }}
| image2 = h-SnBr2-xtal-packing-2x2x2-3D-bs-17.png
| caption2 = hexagonal polymorph{{ Cite journal | url = https://www.ccdc.cam.ac.uk/structures/Search?Ccdcid=1737947&DatabaseToSearch=Published | title = ICSD Entry: 429133 | website = Cambridge Structural Database: Access Structures | publisher = Cambridge Crystallographic Data Centre | access-date = 2022-02-09 }}
}}
Preparation
Tin(II) bromide can be prepared by the reaction of metallic tin and HBr distilling off the H2O/HBr and cooling:{{Cotton&Wilkinson6th}}
: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.
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.{{Greenwood&Earnshaw}}
When dissolved in HBr the pyramidal SnBr3− ion is formed.
Like SnCl2 it is a reducing agent. With a variety of alkyl bromides oxidative addition can occur to yield the alkyltin tribromide{{cite journal
| title = A convenient synthesis of (C1-C18) alkyltin tribromides
| author = Bulten E.J.
| journal = Journal of Organometallic Chemistry
| year = 1975
| volume = 97
| issue = 1
| pages = 167–172
| doi = 10.1016/S0022-328X(00)89463-2
| hdl = 1874/15985
| hdl-access = free
}} 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
| title = Synthesis and studies of trimethylamine adducts with tin(II) halides
|author1=Chung Chun Hsu |author2=R. A. Geanangel
|name-list-style=amp | journal = Inorg. Chem.
| year = 1977
| volume = 16
| issue = 1
| pages = 2529–2534
| doi = 10.1021/ic50176a022
}}
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.{{cite journal
| title = Donor and acceptor behavior of divalent tin compounds
|author1=Chung Chun Hsu |author2=R. A. Geanangel
|name-list-style=amp | journal = Inorg. Chem.
| year = 1980
| volume = 19
| issue = 1
| pages = 110–119
| doi = 10.1021/ic50203a024
}}
References
{{reflist}}
{{Tin compounds}}
{{bromides}}