Tin(II) chloride

Tin(II) chloride

Names
IUPAC names Tin(II) chloride Tin dichloride
Other names Stannous chloride Tin salt Tin protochloride
Identifiers
CAS Number	7772-99-8 Y 10025-69-1 (dihydrate) N
3D model (Jmol)	Interactive image
ChEBI	CHEBI:78067 N
ChemSpider	22887 N
ECHA InfoCard	100.133.348
E number	E512 (acidity regulators, ...)
PubChem	24479
RTECS number	XP8700000 (anhydrous) XP8850000 (dihydrate)
UN number	3260
InChI InChI=1S/2ClH.Sn/h2*1H;/q;;+2/p-2 N Key: AXZWODMDQAVCJE-UHFFFAOYSA-L N InChI=1/2ClH.Sn/h2*1H;/q;;+2/p-2 Key: AXZWODMDQAVCJE-NUQVWONBAJ
SMILES Cl[Sn]Cl
Properties
Chemical formula	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)
Solubility in water	83.9 g/100 ml (0 °C) Hydrolyses in hot water
Solubility	soluble in ethanol, acetone, ether, Tetrahydrofuran insoluble in xylene
Magnetic susceptibility (χ)	−69.0·10−6 cm3/mol
Structure
Crystal structure	Layer structure (chains of SnCl3 groups)
Coordination geometry	Trigonal pyramidal (anhydrous) Dihydrate also three-coordinate
Molecular shape	Bent (gas phase)
Hazards
Main hazards	Irritant, dangerous for aquatic organisms
Safety data sheet	See: data page ICSC 0955 (anhydrous) ICSC 0783 (dihydrate)
NFPA 704	0 1 0
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)
Related compounds
Other anions	Tin(II) fluoride Tin(II) bromide Tin(II) iodide
Other cations	Germanium dichloride Tin(IV) chloride Lead(II) chloride
Supplementary data page
Structure and properties	Refractive index (n), Dielectric constant (εr), etc.
Thermodynamic data	Phase behaviour solid–liquid–gas
Spectral data	UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Tin(II) chloride, also known as stannous chloride, is a white crystalline solid with the formula SnCl₂. It forms a stable dihydrate, but aqueous solutions tend to undergo hydrolysis, particularly if hot. SnCl₂ is widely used as a reducing agent (in acid solution), and in electrolytic baths for tin-plating. Tin(II) chloride should not be confused with the other chloride of tin; tin(IV) chloride or stannic chloride (SnCl₄).

SnCl₂ has a lone pair of electrons, such that the molecule in the gas phase is bent. In the solid state, crystalline SnCl₂ forms chains linked via chloride bridges as shown. The dihydrate is also three-coordinate, with one water coordinated on to the tin, and a second water coordinated to the first. The main part of the molecule stacks into double layers in the crystal lattice, with the "second" water sandwiched between the layers.

Tin(II) chloride can dissolve in less than its own mass of water without apparent decomposition, but as the solution is diluted hydrolysis occurs to form an insoluble basic salt:

Therefore, if clear solutions of tin(II) chloride are to be used, it must be dissolved in hydrochloric acid (typically of the same or greater molarity as the stannous chloride) to maintain the equilibrium towards the left-hand side (using Le Chatelier's principle). Solutions of SnCl₂ are also unstable towards oxidation by the air:

This can be prevented by storing the solution over lumps of tin metal.

There are many such cases where tin(II) chloride acts as a reducing agent, reducing silver and gold salts to the metal, and iron(III) salts to iron(II), for example: