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| Names | |||
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| IUPAC names Tin(II) chloride Tin dichloride | |||
Other names
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| Identifiers | |||
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3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider |
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| DrugBank | |||
| ECHA InfoCard | 100.028.971 | ||
| EC Number |
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| E number | E512(acidity regulators, ...) | ||
| RTECS number |
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| UNII |
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| UN number | 3260 | ||
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| Properties | |||
| SnCl2 | |||
| Molar mass | 189.60 g/mol (anhydrous) 225.63 g/mol (dihydrate) | ||
| Appearance | White crystalline solid | ||
| Odor | odorless | ||
| Density | 3.95 g/cm3 (anhydrous) 2.71 g/cm3 (dihydrate) | ||
| Melting point | 247 °C (477 °F; 520 K) (anhydrous) 37.7 °C (dihydrate) | ||
| Boiling point | 623 °C (1,153 °F; 896 K) (decomposes) | ||
| 83.9 g/100 ml (0 °C) Hydrolyses in hot water | |||
| Solubility | soluble inethanol,acetone,ether,Tetrahydrofuran insoluble inxylene | ||
| −69.0·10−6 cm3/mol | |||
| Structure | |||
| Layer structure (chains of SnCl3 groups) | |||
| Trigonal pyramidal (anhydrous) Dihydrate also three-coordinate | |||
| Bent (gas phase) | |||
| Thermochemistry | |||
Std enthalpy of formation(ΔfH⦵298) | −325 kJ/mol | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | Irritant, dangerous for aquatic organisms | ||
| GHS labelling:[2] | |||
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| Danger | |||
| H290,H302+H332,H314,H317,H335,H373,H412 | |||
| P260,P273,P280,P303+P361+P353,P304+P340+P312,P305+P351+P338+P310 | |||
| NFPA 704 (fire diamond) | |||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 700 mg/kg (rat, oral) 10,000 mg/kg (rabbit, oral) 250 mg/kg (mouse, oral)[1] | ||
| Safety data sheet (SDS) | ICSC 0955 (anhydrous) ICSC 0738 (dihydrate) | ||
| Related compounds | |||
Otheranions | Tin(II) fluoride Tin(II) bromide Tin(II) iodide | ||
Othercations | Germanium dichloride Tin(IV) chloride Lead(II) chloride | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Tin(II) chloride, also known asstannous chloride, is a whitecrystalline solid with the formulaSnCl2. It forms a stabledihydrate, butaqueous solutions tend to undergohydrolysis, particularly if hot. SnCl2 is widely used as areducing agent (in acid solution), and inelectrolytic baths fortin-plating. Tin(II) chloride should not be confused with the other chloride of tin;tin(IV) chloride or stannic chloride (SnCl4).
SnCl2 has alone pair ofelectrons, such that the molecule in the gas phase is bent. In the solid state, crystalline SnCl2 forms chains linked viachloride bridges as shown. The dihydrate has three coordinates as well, with one water on the tin and another water on the first. The main part of the molecule stacks into double layers in thecrystal lattice, with the "second" water sandwiched between the layers.
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Tin(II) chloride dissolves in less than its own mass of water. Dilute solutions are subject to hydrolysis, yielding an insoluble basic salt:
Hydrolysis is prevented in the presence ofhydrochloric acid, typically of the same or greater molarity as the stannous chloride. Solutions of SnCl2 are also unstable towardsoxidation by the air:
Oxidation can be prevented by storing the solution over lumps of tin metal.[4]
Tin(II) chloride acts as a reducing agent forsilver andgold salts to the metal, and iron(III) salts to iron(II), for example:
It also reduces copper(II) to copper(I).
Solutions of tin(II) chloride can also serve simply as a source of Sn2+ ions, which can form other tin(II) compounds viaprecipitation reactions. For example, reaction withsodium sulfide produces the brown/blacktin(II) sulfide:
Ifalkali is added to a solution of SnCl2, a white precipitate of hydratedtin(II) oxide forms initially; this then dissolves in excess base to form a stannite salt such as sodium stannite:
Anhydrous SnCl2 can be used to make a variety of tin(II) compounds in non-aqueous solvents. For example, thelithiumsalt of4-methyl-2,6-di-tert-butylphenol reacts with SnCl2 inTHF to give the yellow linear two-coordinate compound Sn(OAr)2 (Ar =aryl).[5]
Tin(II) chloride also behaves as a weakLewis acid, formingcomplexes withligands such aschloride ion, for example:
LikeSnCl2(H2O),trichlorostannate (SnCl−3) ion ispyramidal. Such complexes have a fulloctet. Thelone pair of electrons in such complexes is available for bonding. Therefore,SnCl−3 itself can serve as aLewis base or ligand:[6]
SnCl2 can be used to make a variety of related compounds containing metal-tin bonds. For example, the reaction withdicobalt octacarbonyl:
Anhydrous SnCl2 is prepared by the action of dryhydrogen chloride gas ontin metal. The dihydrate is made by a similar reaction, usinghydrochloric acid:
The water then carefully evaporated from the acidic solution to produce crystals of SnCl2·2H2O. This dihydrate can bedehydrated to anhydration usingacetic anhydride.[7]
A solution of tin(II) chloride containing a littlehydrochloric acid is used for thetin-plating of steel, in order to maketin cans. An electric potential is applied, andtin metal is formed at thecathode viaelectrolysis.
Tin(II) chloride is used as amordant in textiledyeing because it gives brighter colours with some dyes e.g.cochineal. This mordant has also been used alone to increase the weight of silk.
In recent years, an increasing number oftooth paste brands have been adding Tin(II) chloride as protection against enamel erosion to their formula, e. g.Oral-B orElmex.
It is used as a catalyst in the production of the plasticpolylactic acid (PLA).
It also finds a use as a catalyst between acetone and hydrogen peroxide to form the tetrameric form ofacetone peroxide.
Tin(II) chloride also finds wide use as areducing agent. This is seen in its use for silvering mirrors, wheresilver metal is deposited on the glass:
A related reduction was traditionally used as an analytical test forHg2+ (aq). For example, if SnCl2 is addeddropwise into a solution ofmercury(II) chloride, a white precipitate ofmercury(I) chloride is first formed; as more SnCl2 is added this turns black as metallic mercury is formed.
Stannous chloride is also used by many precious metals refining hobbyists and professionals to test for the presence ofgold salts.[8] When SnCl2 comes into contact with gold compounds, particularlychloroaurate salts, it forms a bright purple colloid known aspurple of Cassius.[9] A similar reaction occurs withplatinum andpalladium salts, becoming green and brown respectively.[10]
When mercury is analyzed using atomic absorption spectroscopy, a cold vapor method must be used, and tin (II) chloride is typically used as the reductant.
Inorganic chemistry, SnCl2 is used in theStephen reduction, whereby anitrile is reduced (via animidoyl chloride salt) to animine which is easily hydrolysed to analdehyde.[11]
The reaction usually works best witharomatic nitrilesAryl-CN. A related reaction (called the Sonn-Müller method) starts with an amide, which is treated withPCl5 to form the imidoyl chloride salt.
The Stephen reduction is less used today, because it has been mostly superseded bydiisobutylaluminium hydride reduction.
Additionally, SnCl2 is used to selectively reducearomaticnitro groups toanilines.[12]
SnCl2 also reducesquinones tohydroquinones.
Stannous chloride is also added as afood additive withE numberE512 to some canned and bottled foods, where it serves as acolor-retention agent andantioxidant.
SnCl2 is used inradionuclide angiography to reduce the radioactive agenttechnetium-99m-pertechnetate to assist in binding to blood cells.
Molten SnCl2 can be oxidised to form highly crystalline SnO2 nanostructures.[13][14]
A Stannous reduction is used innuclear medicinebone scans to remove the negative charge from freepertechnetate when it is bound to MDP for radiopharmaceutical studies. Incomplete reduction due to insufficient tin or accidental insufflation of air leads to the formation of free pertechnetate, a finding which can be seen on bone scans due to its inappropriate uptake in the stomach.[15]
Stannous Chloride is used for coating SnO2 Tin Oxide doped conductiveiridescent coatings for low e glass.[16]
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